Talk:Mercury (planet)/Archive 2

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Please add the Unicode of the Mercury symbol ☿ (xml->& #9791;) in addition to the .svg file. (talk) 21:24, 7 August 2009 (UTC)

Cilcle of 87969 days

Wanted to fill in how much years it takes to fulfill 87969 days. And that is approximately earthen 241 years. -- (talk) 16:51, 29 September 2009 (UTC)


Since this mission that is still in the planning phase and is subject to revision or cancellation, it seems difficult to justify why it has such a large section in this article. I think that section should be trimmed to a single paragraph or removed entirely (replaced with a link in the "See also" section) until the spacecraft actually reaches Mercury. Thoughts?—RJH (talk) 17:45, 21 October 2009 (UTC)

I trimmed out most of the material that was not directly related to Mercury.—RJH (talk) 18:20, 28 October 2009 (UTC)

Apparent visual magnitude for Mercury

The apparent visual magnitude for Mercury in the main article is given as: -2.0 to 5.5.

At its brightest Mercury reaches magnitude –2.3, a figure that may be computed from the formula given in the Astronomical Ephemeris or the old Nautical Almanac (HMSO).

When in transit of the Sun, Mercury is sensibly black since unlike Venus it has no atmosphere to enable light to be conveyed to the side facing Earth. At other times, the diminution in brightness close to inferior conjunction can take the planet well below magnitude 5.5.

Wilberfalse (talk) 21:59, 25 November 2009 (UTC)

The two references from NASA give -1.9 and 5.7 (May 2002). I am not sure we need to worry about extreme scenarios and any numbers used should be properly referenced with a reliable website. -- Kheider (talk) 23:50, 25 November 2009 (UTC)

Since the geometry in these arguments refers to the centre of both bodies, Sun and Mercury, even during a transit of the Sun’s disc (unless the centres coincide, and I have not computed a date when this is likely to happen, if at all) Mercury will have a magnitude between infinity and “something”.

I agree from a practical point of view it may be splitting hairs a little to argue over these limits but it does need to be pointed out that the choice of a minimum brightness at magnitude 5.5 is itself somewhat arbitrary.

I am also prepared to admit that the formulae used in these calculations are not set in stone: I speak from over fifty years experience of computing ephemeredes for various publications including for the International Astronomical Union and others.

As a matter of observational fact, I have on several occasions observed Mercury close to superior conjunction using small refractors (85 mm to 100 mm aperture) to within 2 arc-degrees of the Sun’s limb.

Wilberfalse (talk) 17:25, 26 November 2009 (UTC)

JPL Horizons shows Mercury at apmag –2.4 on 2006-May-18 04:45UT, but of course Mercury is only 0.79° from the magnitude –26 Sun. When Mercury is 4° from the Sun it is only mag –1.9. I have changed the range to show "–2.3 (May 19 2002) to 5.7 (May 28 2002)" -- Kheider (talk) 18:41, 26 November 2009 (UTC)

"Mercury (planet)" -> "Mercury"

Should this article not be moved to "Mercury" and whatever occupies that name moved to "Mercury (whatever the type is)"? All of the other planets have the primacy of the titles; even Pluto occupies "Pluto" and not "Pluto (dwarf planet)"! I am fairly certain that the planet is the first thing most people think of when hearing the name Mercury; why does the article title not match this? -RadicalOneContact MeChase My Tail 22:40, 6 February 2010 (UTC)

Are you sure? What about Mercury (element)? I'm pretty sure most people would think of that first. Serendipodous 22:46, 6 February 2010 (UTC)
I don't, but I agree that is another prolific use of the name. However, given that the other planets all dominate their names, why is Mercury an exception? Mercury (element) is not in the "main" position either. -RadicalOneContact MeChase My Tail 23:00, 6 February 2010 (UTC)
Because, unlike the other planet names, there is no consensus on which article describes the most common use of the term. Serendipodous 23:03, 6 February 2010 (UTC)
Except the element is not used in a way to hold that position either...a disambiguation page is. -RadicalOneContact MeChase My Tail 23:13, 6 February 2010 (UTC)
Exactly. They're both equal. Serendipodous 23:25, 6 February 2010 (UTC)

I may be wrong on this, but it appears that the default procedure is to make one article the "main" one, with regards to consistency, and then make the other a "this is about the [object]. For the [other object, see [name] ([other object]). -RadicalOneContact MeChase My Tail 23:31, 6 February 2010 (UTC)

Yep. WP:PRIMARYTOPIC.—RJH (talk) 03:02, 7 February 2010 (UTC)
I'd actually prefer to have the planet's article at Mercury as well, even if only for a standard presentation. I think we could make the case if it were simply a decision between the planet and the god, as with other astronomy articles. Unfortunately, it is hard to argue a primary topic when one subject is a planet and another is an element. --Ckatzchatspy 08:27, 7 February 2010 (UTC)
Could the argument for consistency be made? -RadicalOneContact MeChase My Tail 15:36, 7 February 2010 (UTC)
I'm with Serendipodous on this one. The element Mercury is a significant article, so that planet Mercury is by no means the overwhelming topic of choice. Per WP:PRIMARYTOPIC, in this case I don't think we can select one article above the others to be the primary. The other planets don't have an equally weighty article with the same name, so in their cases they can be the primary article.—RJH (talk) 16:21, 7 February 2010 (UTC)

IMHO, the way it is now is best. As much as I like astronomy, Mercury (planet) has no right to claim priority of Mercury (element). It is best and fairest to treat them as equals. -- Kheider (talk) 18:25, 7 February 2010 (UTC)

I agree Raywil (talk) 23:03, 7 February 2010 (UTC)
For what is worth, I've looked at a random sample from the Corpus of Contemporary American English and references to the planet and those to the metal were nearly in the same number (within a factor of 2 of each other). A quick glance at a similar sample from the British National Corpus doesn't show a clear predominance of either meaning. ― A._di_M.3rd Dramaout (formerly Army1987) 07:39, 28 June 2010 (UTC)

Super-human feat?

I just wanted to point out what appears to be a super-human feat. The following was recently added to the text:

In the 12th century, Ibn Bajjah observed "two planets as black spots on the face of the Sun," which was later identified as the transit of Mercury and Venus by the Maragha astronomer Qotb al-Din Shirazi in the 13th century.

The average angular resolution of the human eye is one minute of arc. At inferior conjunction, Venus has an angular size of about 67 arc seconds, or 1.1 arc minutes. Thus it is plausible that Venus could be perceived. Mercury, however, has a maximum angular size of 13 arc seconds. This is 0.22 arc minutes, or one-fifth the average resolution of the human eye. Ibn Bajjah must have had pupils the size of binocular lenses to accomplish this feat.

Conversely, there have been records of people seeing sun spots dating back to the seventeenth century. Per this article, a sun spot is visible to the unaided eye when it is 50 arc seconds in diameter.

The cited reference states:
It is interesting to note that in connection with the transit of Venus he [Abu Talib] mentions the name of Quotbuddin Shirazi (1236-1311), to whom it was known. We know today that Ibn Sina (d. 1073), Ibn Bajja (d. 1138) and others had observed "the two planets as black dots on the face of the Sun", evidently due to the transit(s) of Venus and/or Mercury. In fact, Quotbuddin has referred to the observation of the Venus transit by Ibn Bajja.
It is unclear whether the assertion about the transit(s) of Venus and/or Mercury was due to the observers or to the author of the Journal article. My sense in this is that the citation makes it plausible that the Venus transit was observed, but the observation of a Mercury transit is more dubious.
There was apparently an 807 report, during the era of Charlemagne, about a dark spot on the face of the Sun. Astronomers at the time interpreted this as a transit of Mercury. However, the spot was seen for eight days, making a transit unlikely.[1]RJH (talk) 18:16, 6 March 2010 (UTC)—RJH (talk) 19:44, 7 March 2010 (UTC)

Article size

The Mars article has a separate History of Mars observation article to cover the details that are included in this article's "Ancient astronomers" and "Ground-based telescopic research" sections. Would that make sense here? In this article, the "Research with space probes" section could be trimmed by removing the information that is not directly relevant to Mercury. E.g. the orbital maneuvering, fly-bys of other planets, and the loss of fuel. Any objections to these ideas?—RJH (talk) 14:56, 7 May 2010 (UTC)


Why is Mercury 200*F - 800*F and Venus is only 900*F? Because Mercury is the first planet from the Sun. Cpcheats (talk) 17:25, 29 May 2010 (UTC)

Because Venus has a CO2 atmosphere that increases surface temperatures. Serendipodous 17:36, 29 May 2010 (UTC)
Venus' CO2 atmosphere keeps heat from escaping the planet. Thus, even though Mercury is closer, Venus' surface temperature is hotter. -- (talk) 04:04, 28 June 2010 (UTC)

because mercury has no clouds to trap the heat but Venus has many clouds so that the heat will not escape. —Preceding unsigned comment added by (talk) 13:52, 8 June 2010 (UTC)

Smallest or 2nd Smallest Planet?

When they said "Mercury is the smallest Planet in the Solar System", I thought it was the second smallest Planet in the Solar System. Because first they discovered Pluto in 1930, then they changed it to a Dwarf Planet in 2005, and then they changed it to a Planet again in 2008-2009. So shouldn't Mercury be the second smallest Planet in the Solar System? Please answer right when you find this question!!! Cpcheats (talk) 17:34, 29 May 2010 (UTC)

The IAU has not reversed its decision on Pluto. It's still not a planet. Serendipodous 17:35, 29 May 2010 (UTC)
Also, for the record Mercury is much more massive and physically larger than Pluto, no matter what you call Pluto. :-) -- Kheider (talk) 13:57, 8 June 2010 (UTC)


The hatnote I added was removed with the edit summary "Mercury does not redirect here". Well, Mercury doesn't redirect to Mercury (element) either, but that article does have a hatnote. Why? ― A._di_M.3rd Dramaout (formerly Army1987) 07:34, 28 June 2010 (UTC)

Looks like the hatnote was just removed from Mercury (element) as well, because of WP:NAMB.—RJH (talk) 17:02, 28 June 2010 (UTC)

Conjunction Mercury, Venus and moom

Is it possible this File:Mercury, Venus and the Moon Align.jpg conjunction? OTAVIO1981 (talk) 11:32, 24 September 2010 (UTC)

Nice picture. And perfectly possible - why not? (In fact I think I saw one a few years ago.) Rothorpe (talk) 15:27, 24 September 2010 (UTC)
I thought Mercury was too far away from the Sun. OTAVIO1981 (talk) 17:36, 24 September 2010 (UTC)
It happened March 6, 2008. I looked it up on skyviewcafe, a planetarium program. The location and month were here. Saros136 (talk) 18:54, 24 September 2010 (UTC)
Skyviewcafe is here . I used the search to find Antofagasta, Chile, about 120 km away from the observatory. Saros136 (talk) 19:03, 24 September 2010 (UTC)

IPA redo

I suggest that the IPA pronounciation of "Mercury" should be redone to the standards of the International Phonetic Alphabet, not the English version because non-english speakers would read the "r" and say a trill rather than "ɹ" which is the correct IPA letter for r as in "bird". —Preceding unsigned comment added by Agrasa (talkcontribs) 00:44, 17 November 2010 (UTC)

You're confusing the phoneme [r] with its allophone [ɹ]. I'm British, and don't pronounce any 'r' sound in 'bird' (allophone: [ ]). Rothorpe (talk) 23:25, 23 December 2010 (UTC)

How Long is a Century

This article says the precession of the perihelion is at an excess of "43 arcseconds per century". Is that an Earth century or a Mercury century and, more importantly, should the article make that distinction clear? (talk) 12:34, 19 December 2010 (UTC)

Earth's, of course. Mercury does not have centuries. Ruslik_Zero 18:36, 19 December 2010 (UTC)
A "day" is how long it takes to revolve on its own axis; a "year" is how long it takes to revolve around the sun. Why does it not have centuries, which would simply be a hundred revolutions around the sun? And, more importantly, was your answer based on your incorrect assertion or vice versa? (talk) 12:16, 22 December 2010 (UTC)
It's safe to say in any astronomical context that when a time period (days or years) that could be applied to different bodies is mentioned without specifying the body, it's referring to Earth time. --Patteroast (talk) 06:52, 23 December 2010 (UTC)
It's also not clear that terms like decade, century or millennium would be meaningful in the context of Mercury-based time-keeping. Those are words that are typically applied as a convenience in the context of human history.—RJH (talk) 20:15, 23 December 2010 (UTC)


Is it time to protect this article? -- Kheider (talk) 19:13, 11 January 2011 (UTC)

There have been a few useful edits by anonymous editors over the past month, so we would risk losing that.—RJH (talk) 16:28, 12 January 2011 (UTC)

Edit request from Bvera234, 2 March 2011

{{edit semi-protected}} it takes mercury 59 earth days. Bvera234 (talk) 23:14, 2 March 2011 (UTC)

Already in the article. Materialscientist (talk) 23:25, 2 March 2011 (UTC)

Magnetic field and magnetosphere

Hi, I'm traslating this article in italian and I have found some inaccuracies:

Does Mercury have radiation belts? Here, the Article states that «The planet's magnetosphere, though small enough to fit within the Earth,[62] is strong enough to trap solar wind plasma» however, Van Allen (1999) and Slavin (2007) say that there aren't radiation belts around Mercury. Van Allen, also, is the same source numbered as [62] in the sentence.

Again, the Article states that «Unlike Earth, however, Mercury's poles are nearly aligned with the planet's spin axis. [65]», while the same source number [65] specifies also the value (dipole tilt ~ 10°). Earth tilt is just 11,3°! Anderson (2010) states that the dipole tilt value should be less than 5°. So, it would be possible to specify the value, without the comparison with the Earth.

Lastly, «It is likely that this magnetic field is generated by way of a dynamo effect, in a manner similar to the magnetic field of Earth.[66][67]» However Christensen (2006), the same [67], states: "the low intensity of Mercury’s magnetic field [...] cannot be reconciled with an Earth-like dynamo".

Bie. --Harlock81 (talk) 10:28, 3 March 2011 (UTC)


With Messenger in orbit, I'd imagine that findings will start coming in a flood now. The article may get overwhelmed with a multitude of minor additions and badly formed citations.—RJH (talk) 18:05, 18 March 2011 (UTC)

We've got a while yet; it will be weeks before the actual science starts coming in. But yes, we need to be on our guard. Serendipodous 19:29, 18 March 2011 (UTC)

Article Tone Too Academic

Hello, I'm a 34 yr old computer programmer with a strong science background, and even I find this article exceedingly dry and academic to the point of being unreadable. I even checked the URL again to make sure I was on wikipedia and not some other -pedia for specialists. I came to this page for two pieces of information: the size of Mercury and its distance from the sun. I began by reading the introduction, which informs me "The perihelion of Mercury's orbit precesses around the Sun at an excess of 43 arcseconds per century," which seems to have been regarded as so important as to be the second sentence. After wading through all of this gibberish, I finally discovered the information I was looking for, buried among similar gibberish in the right-hand column. I can only infer that the distance from the sun is the labeled by the aphelion and perihelion.

Please keep in mind that Mercury is one of the nine planets (er, eight now, I guess) memorized by every schoolchild in first or second grade, not some obscure academic topic. It might be worthwhile to clean up the introduction, at least, to give some physical and orbital characteristics of Mercury in as plain an english as possible, before venturing into more obscure matter. For example, the physical appearence of mercury, the distance from the sun compared to that of Earth's distance and it's size, as well as fun tidbits such as, e.g. how large the sun looks from its surface (and there's already some good stuff like this).

Anyway, chalk up one vote for cleaning up the article's tone. (talk) 04:01, 31 March 2011 (UTC)

Forgive me for being blunt, but the information you were seeking is included in the infobox on the right. It is very useful for people as yourself, who are looking for a quick reference material. --Xession (talk) 04:04, 31 March 2011 (UTC)
Yes, as I explained, I found the distance from the sun labeled as 'aphelion' and 'perihelion', words not commonly known to most college graduates. (talk) 06:12, 31 March 2011 (UTC)
Most concepts in the infobox, as with most other science related concepts, are linked to articles that describe those concepts in depth. Alternately, for faster information referencing that does not require further reading, I might suggest Google or WolframAlpha.
No shit, is that why the words are in blue? And thanks for that link to Google, asshole. - (talk) 02:56, 4 April 2011 (UTC)
Such a pleasant attitude for someone seeking help.--Xession (talk) 03:01, 4 April 2011 (UTC)
Despite his uncivil tongue and boorish behavior, he does have something of a point. The first four sentences of the lead don't quite satisfy the engaging prose requirement of the FA criteria. :-) Regards, RJH (talk) 15:55, 5 April 2011 (UTC)

Should we add "Mean orbital radius" to the infobox, just for clarity? Serendipodous 07:47, 31 March 2011 (UTC)

distance from sun in the sky

would it be much to ask that, near one of the references to the sight of mercury being obscured by the glare of the sun, to (calculate and) note the maximum distance mercury can appear from the sun in the sky? I honestly don't know how to do that myself. --— robbiemuffin page talk 14:34, 31 March 2011 (UTC)

This information is located in the second paragraph of the "Observation" section.—RJH (talk) 14:37, 31 March 2011 (UTC)

Length of Mercury Day Discrepancy

On the sidebar, the day length (sidereal rotation period) is listed at 54 Earth days. The year is listed as 88 Earth days, but also as .5 Mercury days. 88 is not equal to (1/2)*54, is this a mistake? Schlitzer90 (talk) 18:12, 26 April 2011 (UTC)

The day on Mercury is 176 Earth's days=2 Mercury's years=3 Mercury's rotation periods. The latter is actually 58.6 days not 54. Ruslik_Zero 18:44, 26 April 2011 (UTC)


So is Mercury brown or grey? (talk) 14:44, 6 July 2011 (UTC)

From what I've seen, my sense is that Mercury is a lot like the Moon: mostly gray with faint hints of various hues. The colors need to be exaggerated to make them plainly visible,[2] but there seem to be a lot of red-browns and pale blues. Regards, RJH (talk) 22:05, 6 July 2011 (UTC)

Messenger reporting sulphur and a large lava plain suggesting volcanism

daily mail article containing a fair bit of interest - is this 'new' news - or old news? it looks like new news to me, but I don't know. Perhaps the article needs a section volcanism on mercury or similar ? EdwardLane (talk) 10:35, 20 June 2011 (UTC)

Is it not obvious the core of Mercury is of a dead star? Just look at the way its made of carbon. This is easy, mercury is transformed via lava and instant cold. The dust barrier just stopped because it became too cold. Mercury was a clean sphere once though therefore it was a star's hardened core incased with crust and well transformed via lava and signature frozen craters like the moon hence wat forms a sphere is immense heat, asteroids made of black carbon hardened liquid or lava which generates the crater surface themselves. Instant heat and cold. It was saturnian, once probably yes. No doubt some process of a dying star is involved here, no moon for the solar system but for venus, just look at its scar.-- (talk) 18:50, 30 September 2011 (UTC)


Does Mercury's optimal visibility really depend on whether the observer is located in the Northern or the Southern hemisphere of the Earth? I can't check the (non-online) reference given for this, and e.g. [3] does not mention this, and indeed claims it is never visible in a totally dark sky, no matter which hemisphere. --Roentgenium111 (talk) 21:21, 30 September 2011 (UTC)

Organic Chemistry

The temperature range on Mercury and the range of elements present should be ideal for organic chemistry to take place. Are there any evidence for organic compounds on Mercury? (talk) 23:26, 30 September 2011 (UTC)

One might speculate that organic compounds could exist near the poles or in subterranean locales.[4] But I haven't heard of any such discovery yet. The high temperatures, near vacuum and solar wind probably strip volatiles from any exposed surface nearer the equator. Regards, RJH (talk) 20:10, 14 October 2011 (UTC)

Requested move

The following discussion is an archived discussion of the proposal. Please do not modify it. Subsequent comments should be made in a new section on the talk page. No further edits should be made to this section.

No consensus to move. Vegaswikian (talk) 05:11, 30 October 2011 (UTC)

Mercury (planet)Mercury – Primary topic. This article has viewed 92973 times back in September and it is the first planet near Venus and the Sun, like Pluto which had been moved. JJ98 (Talk / Contributions) 03:28, 23 October 2011 (UTC)

Would you consider withdrawing this request after comparing these links [5] [6]? Materialscientist (talk) 03:42, 23 October 2011 (UTC)
  • Oppose. No evidence of primary topic. As Materialscientist has cited, Mercury (element) was viewed 130596 during that same time period. Zzyzx11 (talk) 04:25, 23 October 2011 (UTC)
  • Oppose there is no way that the planet could be considered the primary topic when in the same time frame the nominator mentioned the element has 37623 more views.-- (talk) 05:03, 23 October 2011 (UTC)
  • Comment I think for most people, "Hg" is the primary topic, since its something they look at every morning. (talk) 05:34, 23 October 2011 (UTC)
  • Oppose. As already noted, the nom's reasoning is flawed in that the page view stats don't actually favour his/her proposal. It's also slightly amusing that Mercury is the example given at Wikipedia:Disambiguation of a term that clearly has no primary topic and needs a disambiguation page. Jenks24 (talk) 05:59, 23 October 2011 (UTC)
  • Oppose—Sorry but I have to agree with the above arguments. Perhaps what could be done instead is to try and disambiguate any links to the topic "Mercury" within the Wikipedia article space. (Actually there's only a few.) Regards, RJH (talk) 15:55, 23 October 2011 (UTC)
  • Oppose. In 2010, there were 1.4 million page views for the element, 1.3 million for the planet. Kauffner (talk) 05:52, 29 October 2011 (UTC)
The above discussion is preserved as an archive of the proposal. Please do not modify it. Subsequent comments should be made in a new section on this talk page. No further edits should be made to this section.

Edit Request

{{Edit semi-protected}}

Messenger entered orbit on the 17th, not the 18th. See here: —Preceding unsigned comment added by (talk) 03:30, 19 March 2011 (UTC)

Please change from...

"The second is the MESSENGER spacecraft, which attained orbit around Mercury on March 18, 2011,[12] where it will begin mapping the rest of the planet."


"The second is the MESSENGER spacecraft, which attained orbit around Mercury on March 17, 2011,[12] where it will begin mapping the rest of the planet."

and please update the reference [12] from...

to... —Preceding unsigned comment added by (talk) 03:37, 19 March 2011 (UTC)

Done by User:Kheider. — Bility (talk) 05:15, 19 March 2011 (UTC)

The reference to the 1.5 m Hale Telescope links to the wrong Hale Telescope. Please redirect to the Mount Wilson Observatory page — Preceding unsigned comment added by (talk) 04:31, 1 July 2011 (UTC)

Delinked. Materialscientist (talk) 04:47, 1 July 2011 (UTC)

New astronomy: "Daily beast and Newsweek (education)" by author Boris Spadina (Croatia): (talk) 16:00, 5 August 2011 (UTC)

Change obvious typo "Internal structure of Mars" to "Internal structure of Mercury"

Fixed, thanks. Materialscientist (talk) 09:43, 11 November 2011 (UTC)

Could this article possibly be rewritten in conversational English? I was just looking for simple information about why we can't usually see Mercury, as well as when and where we can see it. I probably would have stayed for the rest, except that the first section was simply incomprehensible. The writing is factually correct, I'm sure, but I can only understand about half of it because of all the technical jargon. People come to Wikipedia for quick information, not for a college-level education. The articles need to be correct, but they should also be broadly approachable. — Preceding unsigned comment added by Carlogesualdo (talkcontribs) 02:06, 28 December 2011 (UTC)

Maybe this? Many wikipedia articles have a "Simple English" version, which can be found in the left panel, among other language versions (sorted alphabetically). Materialscientist (talk) 03:07, 28 December 2011 (UTC)

Edit request on 13 February 2012

The onmouseover caption of "Synodic period" on the planet specifications is wrong. It says "orbital period"

Zitronic (talk) 13:42, 13 February 2012 (UTC)

Synodic period is defined under orbital period. -- Kheider (talk) 14:27, 13 February 2012 (UTC)
X mark.svg Not done per above - andy4789 · (talk? contribs?) 23:54, 13 February 2012 (UTC)
Sorry but I didn't say it wasn't defined. I said the onmouseover caption was wrong. Screenshot — Preceding unsigned comment added by Zitronic (talkcontribs) 19:04, February 15, 2012
This isn't an error. Synodic period is a redirect which points to Orbital period, because "synodic period" doesn't have its own article. When you mouse over the wikilink, it shows you the page it redirects to. elektrikSHOOS (talk) 19:18, 15 February 2012 (UTC)

All that being said, it's hard to figure out what the Synodic period in this article's info box means using the def in Orbital period.--agr (talk) 22:48, 15 February 2012 (UTC)


The info panel on the right of the page says the average surface temperature varies from 340K at the equator to 200K at the poles, but the main text says the overall average surface temperature is 442.5K. This is not physically possible. — Preceding unsigned comment added by (talk) 21:49, 6 February 2012 (UTC)

Yes, I have no idea where the temperatures in the infobox come from. They need better referencing. Regards, RJH (talk) 22:21, 6 February 2012 (UTC)

Thanks. It may be that the info panel is correct and NASA's figure is wrong. Stefan-Boltzmann has been badly misapplied to hemispheres. See — Preceding unsigned comment added by (talk) 09:19, 7 February 2012 (UTC)

While the blog apparently isn't peer reviewed, I think the argument is strong enough to remove the inconsistent 442.5K figure from the text.--agr (talk) 16:25, 7 February 2012 (UTC)
It's only inconsistent if we have a valid reference for the infobox data. Do we? (They seem also to contradict the value of 167K maximum "on the polar plains" given (and referenced) in Geology of Mercury, and the 90K minimum claimed in the lede.) --Roentgenium111 (talk) 17:12, 7 February 2012 (UTC)
I found this, but I haven't had a chance to check the references it cites. --agr (talk) 18:36, 7 February 2012 (UTC)

This reference from the blog might do: , however it makes the point that the temperature a few centimeters below the surface experiences much smaller temperature swings and converges to a constant, year round level, well above the mean surface temperature, at less than a meter depth. This was measured on the moon by the ALSEP experiments on Apollo 15 and 17. So just reporting surface temp may be misleading.--agr (talk) 16:34, 9 February 2012 (UTC)

Yes, the numbers given can roughly be read off Figure 3 (with the "TWO model"), AFAICS. I don't think listing just the surface temperatures is misleading (it's the temperatures relevant for all potential landing missions, unless we can construct "mole-like" landers), but it's certainly a good idea to note the "at depth" temperatures as well. Adding temperatures at 90 degrees of longitude would also be sensible, since Mercury's orbital resonance together with its eccentric orbit lead to large longitudinal temperature changes as well. Mercury seems to be the most complicated planet with respect to surface temperatures... --Roentgenium111 (talk) 20:23, 18 February 2012 (UTC)
I've added the reference to the article. I'd also like to add the actual pole's temperature (180 K max.), but this doesn't seem to work with the infobox's code. Interestingly, temperatures in Mercury's polar regions are constantly below a comfortable 310 K (37° C) from about 87°N 0°W and 85°N 90°W northward, according to Figure 5... --Roentgenium111 (talk) 21:40, 18 February 2012 (UTC)


I would like to remove the mention of the precession of Mercury's orbit at the beginning of this article. There is not yet scientific agreement that there is a net precession of Mercury's orbit. There are some papers confirming 43 arcsecs and some finding zero arcsecs. So, best to remove this until the issue is resolved. D c weber (talk) 21:09, 19 November 2011 (UTC)

Looking at your talk page you seem to have issues with General relativity. I do not agree with removing the content. -- Kheider (talk) 22:53, 19 November 2011 (UTC)
I concur. The precession of Mercury's orbit predicted by general relativity is pretty widely accepted in the scientific community, and Wikipedia isn't the place to contest well-accepted theories. Regards, RJH (talk) 01:10, 20 November 2011 (UTC)

- I grant that most people think that Mercury has a net precession that GRT can account for, but not all. So, in the interest of NPOV, we should mention that Mercury's net precession after subtracting other causes was used to confirm the Einstein GRT and the Lorenz LET relativity theories. And that the precession is still under debate. [Obviously we are debating.] D c weber (talk) 13:15, 8 January 2012 (UTC)

This is an article about Mercury, it is not about your dislike of relativity. -- Kheider (talk) 13:36, 8 January 2012 (UTC)
Then in the interest on NPOV, may I remove the mention of any precession of Mercury's perihelion. i.e. since this has not yet been confirmed that any exists. This way the article is just about Mercury.D c weber (talk) —Preceding undated comment added 00:31, 12 February 2012 (UTC).

There is no need to remove an accepted theory. Even you accept that "most people think that Mercury has a net precession that GRT can account for". -- Kheider (talk) 14:20, 13 February 2012 (UTC)

Yep, WP:WEIGHT definitely applies here. Regards, RJH (talk) 19:33, 8 March 2012 (UTC)

Edit Request

A 3:2 spin-orbit resonance would not make one Mercury day last exactly two Mercury years (this would be a 1:2 spin-orbit resonance). Rather 1 Mercury year would take 1.5 Mercury days (so either footnote 19 or 74 were mis-cited or are wrong). — Preceding unsigned comment added by (talk) 16:55, 22 March 2012 (UTC)

No, the day on Mercury equals exactly two years: 6=1/(1/2-1/3). Ruslik_Zero 18:51, 22 March 2012 (UTC)
A year is 1.5 sidereal days, but 0.5 solar days. — kwami (talk) 18:55, 22 March 2012 (UTC)

Hypothetical origin as the moon of Venus

German Wikipedia says the following (my own translation):

Mercury lacks a natural satellite. A satellite has never seriously been considered for the planet, either. However, since the 1960s, the hypothesis exists that Mercury used to be a satellite itself, which has escaped Venus. Reasons for this assumption are the slow rotation and high eccentricity of its orbit, as well as the surface shape analogous to the Moon, with two strikingly different hemispheres. Using this assumption, it would also be possible to explain why both planets alone in the Solar System are without a moon.

Anyone familiar with this hypothesis? The reasoning appears quite sound, at least to me as a layman. Unfortunately, no source is cited nor is there even a hint at any supporter of the hypothesis; but it would be surprising if mention of a hypothesis so attractive on the surface at least was difficult to locate in the relevant literature – which, I emphasise, I'm not familiar with, therefore my inquiry. --Florian Blaschke (talk) 21:39, 22 April 2012 (UTC)

Not that scenario in particular, but there is some discussion of the topic of a lack of a Venusian moon here: Giant impact hypothesis#Lack of a Venusian moon. Note that Mars doesn't have a native moon either; both Phobos and Deimos were probably captured. I'd imagine the above hypothesis would have some serious issues trying to explain the compositional differences between Venus and Mercury. Regards, RJH (talk) 22:01, 26 April 2012 (UTC)
Theories of Mercury's history involving massive impacts have been essentially disproven by new data from MESSENGER. See doi:10.1126/science.1211576, for example. Since any other escape mechanism would have left detectable evidence in the composition of Mercury, this theory is not taken very seriously, AFAIK. siafu (talk) 23:40, 26 April 2012 (UTC)

Edit request on 28 April 2012

Please edit this page to include the recent discovery of a small 70 meter moon orbiting Mercury.

Verification and more information can be found here

I would do it myself but I don't have the authority.

Ben.echapman (talk) 23:41, 28 April 2012 (UTC)

I'm a little iffy about this change because of WP:UNDUE. Regards, RJH (talk) 03:35, 29 April 2012 (UTC)
This would have made a great DYK hook, if only the source were a little more recent. (talk) 05:18, 29 April 2012 (UTC)
I'm thinking there may be more than one reason to be "iffy" about adding this info. Photoshop much? .. just saying. — Ched :  ?  06:01, 29 April 2012 (UTC)
LOL. Thanks for your link, user:☂. I guess you didn't click on it, Ched? (Sententiously.) Always click on links. darwinbish BITE 08:51, 29 April 2012 (UTC).
Hmm, I guess I did not. It's mildly amusing I suppose. Regards, RJH (talk) 13:52, 29 April 2012 (UTC)

Absolute magnitude

What is the absolute magnitude of Mercury? --JorisvS (talk) 13:25, 11 May 2012 (UTC)

Find the apparent magnitude of the Sun and Mercury at Apparent magnitude#Table of notable celestial objects, then apply the same adjustment used to derive the Sun's absolute magnitude of 4.83. Regards, RJH (talk) 14:48, 11 May 2012 (UTC)
What?? Way too complicated. Using [7] gives me H=−0.705. Can you (or anyone else) confirm this value? --JorisvS (talk) 10:59, 12 May 2012 (UTC)
Ah, different absolute magnitude. My mistake. Shrug. Regards, RJH (talk) 14:57, 12 May 2012 (UTC)

infobox image

Should a false color image be used in the infobox? I dont have a problem with including false color images in the article but am concerned that readers will take away from the article the wrong idea based on that image. This image includes wavelengths not visible to the human eye, namely infrared, which is great for study but not as an identifying image. Are there other full color images (including only visible light), that could be used instead?--RadioFan (talk) 12:54, 30 October 2011 (UTC)

I think you're right, although a natural light image will be rather drab. Regards, RJH (talk) 17:12, 30 October 2011 (UTC)
The purpose of the info-box image is to be identifying, not pretty. If an attractive image can be found that is faithful to what the planet really looks like, that would be fine of course.--RadioFan (talk) 17:28, 30 October 2011 (UTC)
All images are modified to some degree, whether it is in the choice of the exposure, the degree of contrast, the target of the focus, the size of the aperture, or whatever. Hence, my preference is for an accurate representation that is also aesthetically appealing. However, it is important that specifics of the image generation be mentioned in the caption in cases where the image has been significantly modified. Regards, RJH (talk) 19:43, 8 March 2012 (UTC)
I wouldn't call the things you list "modifications", they're necessary conditions for taking any image. I agree with RadioFan in preferring a true-colour image in the infobox, if one is available. --Roentgenium111 (talk) 19:45, 8 April 2012 (UTC)
Okay... so you want to take an image generated from specific frequency scans on a spacecraft and then modify it so as to appear like it would with natural colors. Face-smile.svg Is there a site we can pull it from? Regards, RJH (talk) 20:43, 8 April 2012 (UTC)
I didn't say that; any image taken by an earthly photographer with a "normal" camera (in a high enough resolution) would be fine with me. Unfortunately I don't know how Mercury looks in true colour myself, so it's difficult for me to identify such a photo...--Roentgenium111 (talk) 19:05, 16 April 2012 (UTC)
In any 'early photograph with a "normal" camera' it is just a star-like object. Ruslik_Zero 08:52, 17 April 2012 (UTC)
It should be possible to find something from the unmanned spaceflight forums, I think I've seen some approximate true colour images there. (talk) 21:49, 26 April 2012 (UTC)
@Ruslik0: What I meant was taking a photograph with a normal camera through a sufficiently highly resolving telescope. Earthly telescopes are certainly able to show Mercury as a disc. @IP: If you find one, please post a link here. Thanks! --Roentgenium111 (talk) 10:23, 12 June 2012 (UTC)
The problem is how low Mercury always is in the atmosphere/sky. Any Earth-based image will have horrible turbulence. -- Kheider (talk) 10:34, 12 June 2012 (UTC)
Couldn't you take a picture during a (mid-day) total Solar eclipse, when Mercury is high in the sky? It should be dark enough then... (But as I said above, I'd be happy with any true-colour image, whether space-based or not.) --Roentgenium111 (talk) 14:47, 12 June 2012 (UTC)

Perihelion 5600"/cy vs 574"/cy

At we find "The perihelion precession of Mercury is 5600 arc seconds (1.5556°) per century." This statement is internally inconsistent, as 5600 has only 2 significant figures, buy after conversion the result has 5 significant figures. Can't be. If 5600 arc seconds, then 1.6°, etc. Nicholas Crestone (talk) 19:31, 27 May 2012 (UTC)

At we find "The total observed precession of Mercury is 574.10±0.65 arc-seconds per century[3] relative to the inertial ICFR."

It would appear that at least one of these is wrong. (talk) 13:01, 5 April 2012 (UTC)

Both are correct in their own reference frames. 5600"/century refers to the equinox of date or Earth's moving equinox, whereas 574"/century refers to a fixed equinox or Earth's equinox as it existed at J2000. More specifically, see Simon (1994) and compare §5.9.1 with §5.8.1. For Mercury's perihelion (curly pi), the coefficient of t (millennia not centuries) in §5.9.1 (moving equinox) is 56030.42645"/millennia whereas in §5.8.1 (fixed equinox) it is 5719.11590"/millennia, or 5603.042645"/century vs 571.911590"/century. The latter figure differs from 574.10"/century: Tests of general relativity#Perihelion precession of Mercury mixes old figures from Clemence (1947) with modern figures. The values in both frames of reference should be mentioned to avoid confusion. Another major problem is that most of the current literature only discusses the relativistic difference of 43"/century as if that was the total precession, totally ignoring the moving equinox of 5031"/century and Newtonian perturbations of about 532"/century (ignoring solar oblateness). — Joe Kress (talk) 06:46, 8 April 2012 (UTC)

Adding mention of distance to the Earth

I think it would be worth adding somewhere in the article that Mercury is (on average) the closest planet to the Earth — Preceding unsigned comment added by Gmacks (talkcontribs) 21:34, 23 May 2012 (UTC)

Heh, funny, and you can drown in a river whose average depth is one centimeter. Face-smile.svg Yes it's a curious piece of trivia that may be of interest to the mathematically inclined, and I thank you for posting it. However, I see a few concerns. First it would need a reliable citation; next it would need to be explained to the audience for each of the terrestrial planets; then it would need an explanation as to why it even matters. I'm not so sure it does, although possibly it impacts astronomical observation schedules to some degree. Regards, RJH (talk) 22:46, 23 May 2012 (UTC)
I don't consider this fact notable enough to add; it's an automatic consequence of it being the closest planet to the Sun AFAICS. The Sun itself is even closer to the Earth than Mercury, on average! --Roentgenium111 (talk) 14:14, 12 June 2012 (UTC)

Discovery date in infobox?

I think it would be great if the estimated date of discovery could be added to the infobox. It's believed to have been discovered by the Babylonians around 1370BC as far as I know. In fact I think this info should be provided for all of the planets. Any thoughts on this?Nozzleberry (talk) 17:40, 17 June 2012 (UTC)

As one of the 5 naked eye planets, Mercury has been known for tens of thousands of years. -- Kheider (talk) 18:02, 17 June 2012 (UTC)
Yes, I see your point. On reflection I think that it's 'discovery' date is more when it was understood to be a planet than when it was first spotted as 'wandering star'. I guess this would be when Nicolaus Copernicus first proposed his heliocentric model of the solar system in 1543.Nozzleberry (talk) 19:37, 17 June 2012 (UTC)
Why not Philolaus or Aristarchus of Samos? The discovery date is hopelessly ambivalent so I don't see a need to add this information. Regards, RJH (talk) 19:59, 17 June 2012 (UTC)
Well said! absolutely true. Many thanks for the feedback. RegardsNozzleberry (talk) 22:43, 17 June 2012 (UTC)

The lead seems short, how about...

Mercury is the innermost of the eight planets in the Solar System with a mean distance to the Sun of 0.39 ± 0.09 AU[Not verified in body]. It is also the smallest (about 40% the diameter of the Earth), and its orbit has the highest eccentricity. It orbits the Sun once in about 88 Earth days, completing exactly three rotations about its axis for every two orbits. Mercury has the smallest axial tilt of the Solar System planets meaning that it its axis is almost perpendicular to the plane of its orbit. The orbit itself rotates slowly around the Sun but slightly faster than predicted by classical physics, which was not explained until the 20th century by the General Theory of Relativity.

Belonging to the 4 innermost planets, Mercury is a terrestrial planet with a rocky body like the Earth. It consist of 70% metallic compounds and 30% silicates. Mercury's core has the highest iron content of any planet in the Solar System, and further, Mercury has a magnetic field which is believed to be generated by a molten core heated by tidal forces by the Sun. The planet has no atmosphere and therefore the surface temperature varies by several hundred Kelvin from 700 K at its equator at perihelion to 100 K in its shadow side or at its poles. Its surface resembles the Moon with craters from old meteoroid impacts. A distinctive feature is ridges, up to several hundred kilometers long believed to have been formed as Mercury’s interior cooled and contracted under an already solidified crust.

Being within the orbit of the Earth, it appears as a morning star and an evening star alternatively. It was not until 400 BC that astronomers realized that it was one object and gave it its present name after the messenger of the Greek gods, Hermes or in latin Mercury. Being closer to the Sun than Earth also means that Mercury regularly comes between the Earth and the Sun and sometimes makes a transit. These transits of Mercury are more frequent than transits of Venus due to Mercury's short orbital period, however, its small size makes them more difficult to observe.

Mercury has been observed by telescopes since the 17 century. Even though it is bright, Earth based observations of Mercury are difficult because of its proximity to the Sun. Further, it rotates in a way that means it is normally seen facing the same side towards the Sun and thereby this side is the only visible. This originally led to believe that Mercury was locked with the Sun, keeping the same face towards it. However, Radar observations in the 1960s proved that this was not the case. Since late 20s century Mercury has been visited twice by satellites which have mapped its surface and measured the magnetic field. Traveling to Mercury is challenging because of its high velocity and the attraction from the Sun; both satellites took a gravitational assist from Venus or Earth to reach Mercury.

Soerfm (talk) 20:50, 16 July 2012 (UTC)

Internal structure

Mercury's core is 85% its radius (meaning 85% of its diameter also?), according to new calculations. Mercury’s Surprising Core and Landscape Curiosities, Carnegie Institution for Science, March 21, 2012  Sidelight12 (talk) 07:44, 30 July 2012 (UTC)

Incorrect period of mercury in intro.

In the intro there is a line with an incorrect time it takes Mercury to orbit the Sun once.

"It orbits the Sun once in about 88 Earth days, completing three rotations about its axis for every two orbits. Mercury has the smallest axial tilt of the Solar System planets."

Can I have permission to correct this and change it to approx. 59 days as stated in "Hoff, Darryl B. &; Schmidt, Gary 1979, 'Laboratory exercises in astronomy - the rotation of Mercury', Sky and telescope, vol. 58, no. 3, pp. 219-221."

Jaycastle (talk) 12:03, 1 August 2012 (UTC)

The orbital period is 87.9 days and the rotation period is 58.6 days. 58.6*3=87.9*2. -- Kheider (talk) 12:29, 1 August 2012 (UTC) Sidelight12 (talk) 08:40, 2 August 2012 (UTC)

Sorry guys, I was mislead by a Practical at University which actually referred to the rotation period, not the orbital period :|. Got confused as the rotation period was believed to be 88 days up until the 60's. Jaycastle (talk) 09:18, 2 August 2012 (UTC)


The article states that one day on Mercury lasts two Mercury years. It later says that Mercury rotates three times for every two revolutions around the sun, which would mean that 3 Mercury days = 2 Mercury years. Obviously these cannot both be correct, so which is it? Tad Lincoln (talk) 05:20, 20 August 2012 (UTC)

  • You have a point: it needs clarification. I think it depends on whether we are talking about a sidereal day or a solar day. A solar day is the time that passes from you (standing on Mercury) have the sun over your head and until that happens next time. A sidereal day is the time it takes from you have a certain star (not the sun) above your head and until it happens next. If you look at it this way (and if I have got it right) you will see that 1 solar day = 3 sidereal days = 2 years on Mercury. Soerfm (talk) 19:28, 27 August 2012 (UTC)

Apparent Visual Magnitude

When I lasted contributed to this page in 2009 you adopted my figures for the range in apparent visual magnitude of the planet. I now see a figure of –2.6 given for the planet at its brightest. I am not aware that this has been substantiated either by calculation or by observation, my figure of –2.3 being that adopted for many years as determined from formulae used by established ephemeredes.

My figure for magnitude at the other end of the scale remains at 5.7 but it should be stated that this is an arbitrary figure since when close to the Sun’s limb at inferior conjunction, or indeed at transit, the theoretical magnitude tend towards infinity. — Preceding unsigned comment added by Wilberfalse (talkcontribs) 18:30, 5 September 2012 (UTC)

  • Actually, a thin ring of Mercury's disk is illuminated by the Sun and visible from the Earth even when Mercury appears to be at the centre of the solar disk during a transit. This is because the Sun appears as a large sphere to an observer on Mercury, so it illuminates more than 50% of Mercury's surface. So the visual magnitude of Mercury, seen from Earth, does not tend to infinity during a transit. I have no idea what the figure is, but it's not infinite. It would be brighter, of course, when Mercury is near perihelion than aphelion, since more of Mercury is illuminated, and more brightly. DOwenWilliams (talk) 20:07, 5 September 2012 (UTC)

"Closest planet to Earth and other planets" section

"Averaged over time, Mercury's distance from the Earth is less than that of any other planet. Venus and Mars come closer when they are on the nearby parts of their orbits, but on the more distant parts they go much further away than Mercury. Averaged over a complete orbital cycle, Mercury is about 1.08 Astronomical Units (AU) from Earth. The corresponding distance for Venus is about 1.3 AU. By the same logic, Mercury is the time averaged closest planet to all the others, so it is the closest planet to Jupiter, and so on. (It is, however, not quite as close to Jupiter as the Trojan asteroids, which are the same distance away as the Sun.)[citation needed]"

The numbers were also wrong. For Mercury it is 1.04 au and 1.14 au for Venus. I realize it doesn't need to be exact, but the difference between the two Venus numbers is greater than the difference between the two correct answers. There is another point to be made here though. The time-averaged distances can be gotten with no more math than an averaging function in a spreadsheet. So then the no-OR argument wouldn't apply here. Saros136 (talk) 05:41, 21 September 2012 (UTC)
Some argument validating the use of "time-averaged distance" as a useful or meaningful metric is also needed, otherwise this is very much OR for that reason alone. This is not a quantity that is really mentioned or discussed much in the field of astrodynamics. Additionally, this is still very much OR for the calculations, as well, since while it may seem simplistic to us to do an averaging function in a spreadsheet, it certainly wouldn't be to anyone who has never used spreadsheets or computed averages-- which likely includes the majority of the population of Earth. siafu (talk) 15:46, 21 September 2012 (UTC)
I only meant to argue the point the calculations were OR because they were some advanced math, your second point. Every reader knows what an average is. I'm not fighting to get this included, but suppose I would. I'd just post the spreadsheet, with the numbers and answer. I could even direct them to the cell that contains the average function, so they could see for themselves that the number I call an average really is just that.
And by the way, in some of the planet articles the escape velocity is calculated. The formula is given, but it involves notation most people don't know (or remember) and a square root, which is much less familiar to the average adult than an average. Saros136 (talk) 04:44, 27 September 2012 (UTC)
Tables of escape velocity values for the planets are commonly found in textbooks and references. Time-averaged distance from Earth values are not. siafu (talk) 06:33, 27 September 2012 (UTC)
I understand that. I'm only addressing the argument that time-average is not simple enough not to be OR. You objected that while it may seem simplistic to us to do an averaging function in a spreadsheet, it certainly wouldn't be to anyone who has never used spreadsheets or computed averages-- which likely includes the majority of the population of Earth. It is not necessary for others to repeat the process to confirm it. They could look and see for themselves what was done, and that is very simple, and simpler than following the note to the escape velocity calculation the Wikipedia editors used for their demonstration. Saros136 (talk) 07:16, 27 September 2012 (UTC)
It really doesn't matter how simple the calculations are, the point is that these are novel calculations, and thus OR. They are also unusual and never used quantities, which means that their inclusion here would be (ipso facto) either OR or SYNTH, which is the other point. With escape velocity, I have literally three different books on my shelf that have not only the formula for the calculation (i.e., it's not novel), but also values for the planets and some other larger solar system bodies (i.e., no new calculations required at all). siafu (talk) 19:21, 27 September 2012 (UTC)

I think this section is misleading at best and out-and-out silly at worst. Not to mention it doesn't clearly explain what it means by "Closest planet", and it arrives at that decision by some mathematical technicality. If this section is not removed, then it should at least be clarified, or renamed to "'Closest' planet to Earth and other planets". -- (talk) 03:39, 16 September 2012 (UTC)

Surely, it is no worse than the popular, and usually unexplained, assertion that Venus is the closest planet to the Earth. DOwenWilliams (talk) 03:45, 16 September 2012 (UTC)
Actually, I question the usefulness of the section as well. The fact Venus comes closer to the Earth than other planets is far more important than Mercury's average distance. -- Kheider (talk) 20:25, 16 September 2012 (UTC)
Along with the fact that it was unreferenced, I thought it best to remove this section too. --John (talk) 20:52, 16 September 2012 (UTC)
I checked once to find which planet is most often the closest to Earth, using a program to calculate the distance at daily intervals. It is indeed Mercury. Saros136 (talk) 03:53, 17 September 2012 (UTC)
Did you by any chance calculate it for any other planet? Is the planet most often closest to Mars also Mercury? And for Jupiter? I think that was the point. The statement in the article was also true for every other planet. It was trivia, or an answer to a trick question, more than anything. --RacerX11 Talk to meStalk me 04:12, 17 September 2012 (UTC)
My statement is slightly different, and Mars is most often closest to Jupiter. Saturn has the smallest time-averaged distance, but is never the closest, making the statement in question inaccurate. It is not a trick question. It's not obvious at all, which makes it interesting. (talk) 06:46, 17 September 2012 (UTC)
I made a mistake for Saturn. Mercury does have, barely, the smallest average distance over the interval I used (120,000 distance taken at 3-day intervals beginning at Jan 1, 1900). The averages for the inner planets are all very close. And Saturn can be the closest. Saros136 (talk) 06:59, 17 September 2012 (UTC)
It's pretty easy to prove that, for planets in concentric, independent orbits, the time-averaged closest planet to any of the others is the innermost, Mercury; the next-closest is Venus, and so on. Things get trickier if orbital resonances occur. On average, Trojan asteroids are closer to their parent planets (mostly Jupiter and Neptune) than Mercury. More complex orbital resonances, such as that between Neptune and Pluto, may have interesting effects. I have no idea if Pluto's time-averaged distance from Neptune is greater or less than Mercury's. DOwenWilliams (talk) 15:26, 17 September 2012 (UTC)
That's actually very interesting, yes, but back to the original issue, a better explanation for deletion could then be: Mercury being Earth's time-averaged closest planet has more to do with the properties of orbiting objects in general and nothing to do with their proximity or any special relation between the two. --RacerX11 Talk to meStalk me 22:41, 18 September 2012 (UTC)

──────────────────────────────────────────────────────────────────────────────────────────────────── Should we therefore delete all mentions of the fact that the surface of Mercury is hot? After all, that's just a result of being close to the Sun. If you ask anyone who knows a bit about astronomy which is the closest planet to Earth, and you will almost certainly get the answer "Venus". But in reality, the answer should depend on what is meant by "closest". If is means the planet with the smallest time-averaged distance from Earth, then the correct answer is "Mercury". Surely, this fact is worth mentioning in Wikipedia somewhere, to correct the popular misconception. If not in this article, then where? DOwenWilliams (talk) 01:29, 19 September 2012 (UTC)

When Venus is at inferior conjunction Venus is the closest planet to the Earth. When Mercury is at inferior conjunction, either Venus or Mars can be closer to the Earth. Perhaps this concept would be better added to the orbit article. But since Mercury is a Featured Article, the statements really should have a reference to a reliable source. Wikipedia needs to try and avoid original research. If it is notable someone reliable generally has written about it. -- Kheider (talk) 02:00, 19 September 2012 (UTC)
When Mercury is at inferior conjunction, if Venus and Mars are both on the more distant parts of their orbits, then Mercury is the closest planet to Earth. Actually, if Mercury is at superior conjunction, and Venus and Mars are also near superior conjunction, then Mercury is closest to Earth. Venus is never the closest planet to Earth when it is at superior conjunction. Mercury is always closer. In total, Mercury is the closest planet to Earth for quite a large fraction of the time. DOwenWilliams (talk) 02:35, 19 September 2012 (UTC)
In total, Mercury is the closest planet to Earth for quite a large fraction of the time.. Yes, 47% of the time. This is from the comparison of distances of Mercury,Venus, and Mars from the Earth calculated 10,000 times at intervals of 36 hours. I would like to see the simple statement that Mercury is most often closest to Earth in the article. Saros136 (talk) 04:33, 19 September 2012 (UTC)
At the least, you would have to give a reliable source for your claims, not just private computations. Either way, I don't consider it an encyclopedic fact; in fact, the Sun is on average (and more than half the time) even closer to Earth than Mercury, and thus more often the closest large body to Earth than Mercury. --Roentgenium111 (talk) 14:12, 19 September 2012 (UTC)
There's nothing private about the computations. The data on which they're based are widely published. Anyone with some mathematical skill can duplicate them. This is one of the basic troubles with Wikipedia. It refuses to accept work done by its contributors, who may be highly knowledgeable and who are available to discuss their work, instead relying on citations of writings by people who may or may not be knowledgeable, are generally not available, and may have done the work far enough in the past that it is now outdated or discredited. (See my own user page for a couple of examples of incorrect citations.) Yes. The Sun is closer to Earth than Mercury, in a time-averaged sense. But if we're going to accept it as a "planet", maybe we should count the Moon as the closest large body to Earth. DOwenWilliams (talk) 15:26, 19 September 2012 (UTC)
Wikipedia's reliable source requirements prevent "Youtube researchers" from overrunning people "who may be highly knowledgeable". References allow a reader that may only casually know the subject to check the quality of the source. Footnotes can be used for very simple calculations, but every step of the calculation must be shown. -- Kheider (talk) 17:41, 19 September 2012 (UTC)
This seems to be a good example of how simpleminded analyses of concepts that work well in our daily lives do not work very well in different contexts, specifically the idea of being "closest". Planets are not static entities, and over time different planets will be closer to other planets than at other times due to the nature of objects orbiting a central body. A more meaningful understanding of "closer" might be "more accessible" or "easy to get to", in which case Mercury is NEVER the closest planet to Earth as the required delta-V will always be higher than that needed to get to Mars or Venus. Calling Mercury the "closest planet" to Earth is really quite misleading here, as it would imply that it trumps the two planets in the nearest orbits in terms of close proximity, and could, for example, leave the layperson wondering why it took so long to actually send a probe to orbit Mercury if it's so "close". Similarly, other exploratory techniques, like bouncing RADAR reflections from terrestrial sites off the surface of another planet, were first done on Venus and Mars because they get much closer to Earth than Mercury does. As was pointed out above, by this sort of thinking, the Sun is in fact the closest body to any of the planets, in a "time-averaged" sense; this whole concept of time-averaged proximity is kind of weird, since it's basically saying something like "Often, Earth is closest to Mercury, except when another planet is closer", which is frankly rather tautological. siafu (talk) 21:40, 19 September 2012 (UTC)

Magnetic field contributes to space weathering?

The article states that Mercury's magnetic field contributes to space weathering. This seems counterintuitive - I would expect it to shield it from space weathering by only allowing the solar wind access to the polar regions. I did not find any mention of weathering in the source given after the paragraph. Amaurea (talk) 21:01, 1 December 2012 (UTC)

Temperature extremes

I think the cited temperature range needs a citation, agreed? --maye (talk) 18:09, 14 February 2013 (UTC)

There is already a citation given, in the infobox. --Roentgenium111 (talk) 12:41, 28 May 2013 (UTC)

What does "day" mean?

"Four days after perihelion, the Sun's normal apparent motion resumes." Whenever the word "day" is used, it should always say either "Mercury day" or "Earth day". I think that that example was Earth day, but this ambiguity of "day" should be explained. (talk) 09:29, 21 April 2013 (UTC)

The word "day" appears twice in that short paragraph. The first one was preceded by "Earth". The second, wasn't, but the implication should have been obvious. However, to hammer home the point, I've put "Earth" before the second one too. DOwenWilliams (talk) 14:15, 21 April 2013 (UTC)

"Orbit and rotation" section is useless in understanding why the orbit is so eccentric, comparing to others

Seriously, this article is as old as ancient, and yet it only blatantly states that the orbit of Mercury is the most eccentric without explaining possible reasons for that, as well as history of the planet, and its evolution, including the orbit. I can not believe that astronomy fans have nothing to write about this after all those years. (talk) 09:37, 27 October 2012 (UTC)

Hi, I just want to add here, that I wanted to post a link to a video showing the "two sunrises" on certain spots on Mercury, but the article is semi protected, so I can't do that by myself --Spacenow (talk) 14:47, 1 January 2013 (UTC)
Why do people think that there has to be a reason for the eccentricity of Mercury's orbit? Planets are formed by accretion, as smaller bodies collide and join together. The accidental characteristics of the collisions affect the planet's orbital eccentricity. A small planet is more likely to end up with a large eccentricity than a large one, but basically it's just chance. Venus, which is also small and is adjacent to Mercury, has the smallest orbital eccentricity of all the planets in the solar system. DOwenWilliams (talk) 21:48, 1 January 2013 (UTC)
The article already states that "Simulations indicate that the orbital eccentricity of Mercury varies chaotically from nearly zero (circular) to more than 0.45 over millions of years due to perturbations from the other planets". --Roentgenium111 (talk) 18:10, 29 May 2013 (UTC)

Edit request on 8 June 2013

in the following entry relating to ancient Greek nomenclature for Mercury there are some objectional assertions: The ancient Greeks of Hesiod's time knew the planet as Στίλβων (Stilbon), meaning "the gleaming", and Ἑρμάων (Hermaon).[97] Later Greeks called the planet Apollo when it was visible in the morning sky, and Hermes when visible in the evening. Around the 4th century BC, Greek astronomers came to understand that the two names referred to the same body, Hermes (Ἑρμής: Hermēs), a planetary name that is retained in modern Greek (Ερμής: Ermis).[98] The Romans named the planet after the swift-footed Roman messenger god, Mercury (Latin Mercurius), which they equated with the Greek Hermes, because it moves across the sky faster than any other planet.[99][100]

1) While I think it is true that Stilbon was indeed one name applied to Mercury in Hesiod's time, the only extant uses of that word in Homeric poetry apply to the legendary humans Alexander (Paris) in the Iliad and to Odysseus himself in the Odyssey. So there is not any proof for this assertion prior to the time of Aristotle.Checked this out afresh in TLG 2) The word Hermaon is a misspelling of the Greek Hermaion, and refers not to Hermes himself, but to a "windfall" or "following wind" which the god was thought to provide. 3) The assertion that morning star Mercury was called Apollo and evening star Mercury was called Hermes is likely true, and I wish I could demonstrate it, but cannot. 4) The Greeks, not merely their astronomers, knew that Phosporos and Hesper were the same body and they knew it long before the 4th century. A 4th century pseudo platonic work, Epinomis was the first document WE HAVE to state this, but there is much Greek thought we do not have. 5) Source 98 is valuless. 6) The last sentence has it garbled. Mercury in Roman thought was the quickly plying planet they knew so well. It was equated with Hermes because he, too, was the quickly plying god.

Zinganthropus (talk) 01:14, 8 June 2013 (UTC)

User is now autoconfirmed. No need for the edit request, as the user can now make the changes themselves. Mlpearc (powwow) 18:56, 18 June 2013 (UTC)

Edit request on 8 June 2013

The sections called OBSERVATION, NAKED EYE OBSERVATION, and OBSERVATION HISTORY,would profit from collapsing and re-heading

The call for citations needed around note 90 are wrong. One of these assertions is by definition of what inferior and superior conjunction mean. The other assertions are provable by anyone who knows how to use a computerized planetarium program. Zinganthropus (talk) 01:22, 8 June 2013 (UTC)

User is now autoconfirmed. No need for the edit request, as the user can now make the changes themselves. Mlpearc (powwow) 18:55, 18 June 2013 (UTC)

Supposed highest eccentricity

The remark about Mercury's having the highest orbital eccentricity at 0.205 may be true of the major planets. Minor planets like Pallas have higher ones. — Preceding unsigned comment added by (talk) 11:15, 29 June 2013 (UTC)

That of the orbit of Icarus is 0.82. — Preceding unsigned comment added by (talk) 11:17, 29 June 2013 (UTC)
"solar system's planets" wording is specifically used in lead and 'planet' word is used in whole article. Somewhat like "celestial objects" or "solar system objects" is not used which can confuse readers. So what are you trying to say? neo (talk) 11:45, 29 June 2013 (UTC)

Edit request on 2 July 2013

In the section Naked Eye Viewing the writer says "In successive years the position of Mercury on its orbit shifts by 0.15 revolutions when seen on specific dates, such as the equinoxes.' THE COROLLARY to this is that after 7 years (7x .15 ~ 1.0) the phenomena of the planet repeat themselves almost exactly. This information may prove more useful than the .15/yr. datum. tdw1203 (talk) 23:06, 2 July 2013 (UTC)

Edit request on 2 July 2013

request make Jun 8 resulted in pre approval to edit parts of the Mercury article. Very good but I cannot find out how to exercise this privilege. tdw1203 (talk) 22:43, 2 July 2013 (UTC)

You should see an "edit" link in the top-right corner of the article page. If you need help, ask at the help desk or teahouse. RudolfRed (talk) 03:50, 3 July 2013 (UTC)

Edit request on 2 July 2013

In the section Naked Eye Viewing the writer says "In successive years the position of Mercury on its orbit shifts by 0.15 revolutions when seen on specific dates, such as the equinoxes.' THE COROLLARY to this is that after 7 years (7x .15 ~ 1.0) the phenomena of the planet repeat themselves almost exactly. This information may prove more useful than the .15/yr. datum. tdw1203 (talk) 22:56, 2 July 2013 (UTC)

Already done --ElHef (Meep?) 05:52, 14 July 2013 (UTC)

Roman diety

The introduction to this article states the following concerning Mercury's orbital period:

This rapid motion may have led to it being named after the Roman deity Mercury, the fast-flying messenger to the gods.

I think this is a bit misleading, because in reality the observation of the planet and its orbit predates the Roman deity known as Mercury. The god Mercury is just one aspect of the mythos surrounding the wandering stars, which had many names in different cultures. Perhaps it could be rephrased as:

This rapid motion may have contributed to its association with the Roman deity Mercury, the fast-flying messenger to the gods.

— Preceding unsigned comment added by (talk) 20:52, 10 January 2014 (UTC)

A distinction without a difference. — kwami (talk) 00:18, 28 January 2014 (UTC)

Maximum altitude of Mercury in a dark sky

The sixth paragraph of the "Observation" section currently includes the sentence "In low latitudes and at the right times of year, the ecliptic intersects the horizon at a very steep angle, meaning that Mercury can be relatively high (altitude up to 28°) in a fully dark sky.[citation needed]" 28 degrees is actually the maximum elongation of Mercury from the sun, and astronomical twilight is defined as beginning (or ending) when the sun is 18 degrees below the horizon (see the Wikipedia article on twilight), so this sentence should read "In low latitudes and at the right times of year, the ecliptic intersects the horizon at a very steep angle, meaning that Mercury can be relatively high (altitude up to 10°) in a fully dark sky." Thanks! — Preceding unsigned comment added by Noah Lawes (talkcontribs) 21:43, 22 December 2013 (UTC)

Not done: info in article appears to be sourced. Have you got a source to show otherwise? --Mdann52talk to me! 13:27, 8 January 2014 (UTC)

Thanks for your reply. I have a source for Mercury's maximum elongation of 27.8 degrees from the sun [1] and for astronomical twilight extending to when the sun is 18 degrees below the horizon [2]. Together they prove that the highest Mercury can be in a fully dark sky is 27.8 − 18 ≈ 10 degrees. Noah Lawes (talk) 15:54, 25 January 2014 (UTC)

You're right, of course. I've made the change. DOwenWilliams (talk) 23:41, 25 January 2014 (UTC)

Great, thanks for fixing it! I actually just noticed that the next sentence also isn't true: it says "Such conditions can exist, for instance, after sunset near the Spring Equinox, in March/April for the southern USA and in September/October for South Africa and Australasia. Conversely, pre-sunrise viewing is easiest near the Autumn Equinox.[citation needed][g]" But 27- or 28-degree elongations only occur in the morning sky in March or April and in the evening sky in August or September [3], so this passage could read "Such conditions can exist, for instance, after sunset in August or September for Southern Africa and Australasia, or before sunrise in March or April at similar latitudes." Would you mind fixing this too? Thanks a lot. This sentence could probably also be omitted because the next paragraph deals with it.Noah Lawes (talk) 04:41, 26 January 2014 (UTC)

Deleted. DOwenWilliams (talk) 16:10, 26 January 2014 (UTC)

Splendid, thanks very much!Noah Lawes (talk) 15:36, 9 February 2014 (UTC)

Proposed change in the “Research with space probes” section

I believe that the following statement, from the “Research with space probes” section is misleading:

The potential energy liberated by moving down the Sun’s potential well becomes kinetic energy; requiring another large delta-v change to do anything other than rapidly pass by Mercury.

The sentence would imply that to the delta-v present as a result of the different orbital motions of the Earth and Mercury one has to *add* the delta-v resulting from the potential well of the Sun. In reality, it is easy to show that (1) the delta-v associate to the change in the gravitational potential is the double of the delta-v due to the kinetic energy (from virial theorem) and (2) it has the opposite sign. Indeed the orbital speed is given by

(centripetal force identified with the gravitational one).

The final change in total energy per unit mass to go from orbit 1 to orbit 2 is therefore

Therefore, what really matters is always the difference in the squares of the orbital velocities and nothing else. Moreover, that quantity is not increased (in absolute terms) by the difference of potential energies. I suggest therefore to rephrase the sentence mentioned above to avoid any possible confusion and, if necessary, to refer to the virial theorem for details (the simple relations I wrote here are just to support my statement and I would not include them in the article). Astrozot (talk) 08:58, 19 February 2014 (UTC)

Semi-protected edit request on 16 March 2014

Current infobox image (B&W mosaic)
Proposed infobox image (color photo)

Could someone switch the infobox picture from this image to this image? The current picture is a poorly executed mosaic that makes Mercury look like a flat disc (unlike the mosaic used on the Earth article). Plus the mosaic is black and white, while File:Mercury in color - Prockter07 centered.jpg is full color. In this case I think the color photo has more educational value as it gives a more realistic idea of what Mercury actually looks like. The mosaic should stay in the article, but be switched with the photo. (talk) 20:53, 16 March 2014 (UTC)

it's not clear what changes you want made. Please mention the specific changes in a "change X to Y" format. Should it be switched or should it stay? That last sentence of your request has me confused. — {{U|Technical 13}} (tec) 15:08, 17 March 2014 (UTC)
Just switch the position of the two images (both are already in the article). Nothing complicated. (talk) 17:31, 17 March 2014 (UTC)
Yes check.svg Done You know what, I'm going to go ahead and do that as I agree the non-mosaic image is much more realistic and better looking. It was actually the infobox image for quite a while before someone recently changed it some weeks/months ago. The color one also happens to be a featured image while the mosaic isn't. However, if someone disagrees it may be reverted and we'll have to discuss it first. Cadiomals (talk) 17:55, 17 March 2014 (UTC)

Semi-protected edit request on 23 April 2014

For speed of Mercury it is listed as 47.87 kilometers per second as listed at NASA. You will find that NASA (on some of their sites) has corrected their data after I pointed out to them that this is incorrect. The 47.87 speed assumes a circular orbit while we know it is an ellipse. Distance of circular orbit assuming semi major axis of 57,909,050 is 363,853,292 this yields the value 47.87 kilometers per second while the elliptical orbit, the actual orbit, is 359,975,975 kilometers and assuming year as 87.969 yields the correct value of 47.36200 kilometers per second.

Don Barone Ontario Canada :o)

Ahatmose (talk) 12:24, 23 April 2014 (UTC)

Red information icon with gradient background.svg Not done for now: Please provide an actual reference, rather than the extremely vague "NASA (on some of their sites)" - Thanks - Arjayay (talk) 14:02, 23 April 2014 (UTC)

Hi Don,

Yes, it looks like the 47.8725 km/s came from a circular approximation.

You don't explain what "Phi^2" is and so I don't follow your discussion, but for Mercury's elliptical orbit, a mean of 47.362 km/s is obtained from a MacLaurin series expansion approximating the actual circumference of an ellipse.

The concept of mean velocity is vague and of limited use since the object will almost never be traveling at its mean velocity practically by definition. But I updated the Horizons data-sheet.

Since the actual position and velocity of Mercury can be obtained from Horizons at any instant to within 10's of meters and fractions of a mm/s, based on fits to tracking data and n-body numerical integration of the differential equations of motion, the static data-sheet values in Horizons are FYI "talking values", so one can get a ballpark idea without setting up a run. Horizons doesn't use them, as mentioned in the documentation.

However, thank you for taking the time to point out the problem. If we are going to display a value, we definately want it to be correct, so appreciate your eagle eyes and the effort to track it down!


Jon Giorgini | Navigation & Mission Design Section Senior Analyst | Solar System Dynamics Group | Jet Propulsion Laboratory

But leave it wrong if you insist — Preceding unsigned comment added by Ahatmose (talkcontribs) 14:25, 23 April 2014 (UTC)

Skinakas (hypothetical basin)

I just removed a sentence stating that the Skinakas (hypothetical basin) is currently thought to exist. It doesn't appear to be, and it looks like it was never formally thought to exist. It was sourced to LV Ksanfomality. A person by this name also posits that there are possible photographic images of animals on Venus. Maybe people should review the article, and whether Skinakas (hypothetical basin) should be listed in the Mercury (planet) template as a possible basin or whether it is so discredited at this point it should be removed or deleted.__ E L A Q U E A T E 17:51, 10 May 2014 (UTC)

Semi-protected edit request on 18 May 2014

"it appears to move around its orbit in about 116 days" needs to be changed to 88 days (talk) 20:33, 18 May 2014 (UTC)

No. 116 days is Mercury's synodic orbital period, as seen from the Earth. For example, Mercury is at inferior conjunction every 116 days, on average. Seen from Earth, it appears to go around its orbit every 116 days.
DOwenWilliams (talk) 20:51, 18 May 2014 (UTC)

Semi-protected edit request on 23 April 2014

For speed of Mercury it is listed as 47.87 kilometers per second as listed at NASA. You will find that NASA (on some of their sites) has corrected their data after I pointed out to them that this is incorrect. The 47.87 speed assumes a circular orbit while we know it is an ellipse. Distance of circular orbit assuming semi major axis of 57,909,050 is 363,853,292 this yields the value 47.87 kilometers per second while the elliptical orbit, the actual orbit, is 359,975,975 kilometers and assuming year as 87.969 yields the correct value of 47.36200 kilometers per second.

Don Barone Ontario Canada :o)

Ahatmose (talk) 12:24, 23 April 2014 (UTC)

Red information icon with gradient background.svg Not done for now: Please provide an actual reference, rather than the extremely vague "NASA (on some of their sites)" - Thanks - Arjayay (talk) 14:02, 23 April 2014 (UTC)

Hi Don,

Yes, it looks like the 47.8725 km/s came from a circular approximation.

You don't explain what "Phi^2" is and so I don't follow your discussion, but for Mercury's elliptical orbit, a mean of 47.362 km/s is obtained from a MacLaurin series expansion approximating the actual circumference of an ellipse.

The concept of mean velocity is vague and of limited use since the object will almost never be traveling at its mean velocity practically by definition. But I updated the Horizons data-sheet.

Since the actual position and velocity of Mercury can be obtained from Horizons at any instant to within 10's of meters and fractions of a mm/s, based on fits to tracking data and n-body numerical integration of the differential equations of motion, the static data-sheet values in Horizons are FYI "talking values", so one can get a ballpark idea without setting up a run. Horizons doesn't use them, as mentioned in the documentation.

However, thank you for taking the time to point out the problem. If we are going to display a value, we definately want it to be correct, so appreciate your eagle eyes and the effort to track it down!


Jon Giorgini | Navigation & Mission Design Section Senior Analyst | Solar System Dynamics Group | Jet Propulsion Laboratory

here is the site: corrected speed — Preceding unsigned comment added by Ahatmose (talkcontribs) 15:13, 23 April 2014 (UTC)

But leave it wrong if you insist

Ahatmose (talk) 14:34, 23 April 2014 (UTC)

Red information icon with gradient background.svg Not done: please provide reliable sources that support the change you want to be made. — {{U|Technical 13}} (tec) 13:51, 27 April 2014 (UTC)
The closer Mercury is to the Sun the faster it will move. In 2014, Mecury will vary from about 38.8 km/s to 58.9 km/s (with respect to the Sun). So a generic value of 47 km/s is sufficient as the orbit of Mercury is constantly fluctuating as a result of perturbations. -- Kheider (talk) 21:32, 18 May 2014 (UTC)

Mercury in India's mythology

Budha (in the mythology of India, and not to be confused with Buddha) describes the same god with the same duties as those of the roman deity. Even if most other attributes differ, articles mentioning the one should mention the other, with Mercury yielding priority to Budha. Given that the infant god Budha's origin was both violent and cloaked in mystery, Mercury's planet should mention his origin, if and when reference is made to this story.[4]

  1. ^
  2. ^
  3. ^
  4. ^ Emspak, Jesse (July 6, 2014). "Did Huge Impact Shape Planet Mercury?". Retrieved July 7, 2014. The mysterious makeup of the solar system's innermost planet may be due to a massive "hit and run" collision billions of years ago, a new study reports. 

Pawyilee (talk) 11:31, 7 July 2014 (UTC)

I really don't see how this relates to the planet. Did the Indians give the name '"Budha" to the planet that we call "Mercury"? If so, it would be relevant and interesting. If not, there is no justification for mentioning Budha in this article. DOwenWilliams (talk) 20:01, 7 July 2014 (UTC)
Actually, it is the other way around — "Mercury" is the name given the god, planet and midweek day already named Budha — which is not used for the element called quicksilver. I, however, may be the only person alive on this planet, to read the mythical origin of the infant god Budha as a massive "hit and run" collision between other gods whose names have been given to the other orbs implicated in the planet's origin. —Pawyilee (talk) 05:02, 12 July 2014 (UTC)

naked eye viewing far north

It would seem that sometimes viewing an apparition would sometimes better at high-north latitudes. Saros136 (talk) 11:31, 31 August 2014 (UTC)

Earth days?

Why does the article, and others at times, qualify days with earth? The well–known default meaning of days is earth days. No need to explain. Saros136 (talk) 05:25, 20 August 2014 (UTC)

In the context of talking about the length of a day on another planet, it could be confusing. A little disambiguation doesn't hurt. --Patteroast (talk) 06:40, 20 August 2014 (UTC)
Right, but the phrase is used in other contexts, when there is no risk of a misunderstanding. Such as in the first sentence with an orbital period of about 88 Earth days
Saros136 (talk) 06:55, 20 August 2014 (UTC)

All planets have their own day. When referring to another planet using Earth days, it's important to make this designation. - Benjamin Franklin (talk) 17:02, 31 August 2014 (UTC)

They all do, for sure. But it is not necessary to spell this out, except in certain contexts.
Saros136 (talk) 08:02, 1 September 2014 (UTC)
This is a context where it is IMHO absolutely necessary, especially due to the 3:2 resonance. --cyclopiaspeak! 10:40, 1 September 2014 (UTC)

You can see Mercury now.

I did. Not for long, thanks to a very slow moving cloud. But is very obvious. I'm mentioning this for the benefit of those who have thought it must be very hard to see, so they can check for themselves. It elongation is now about 25°, which is about the angular distance between the thumb and smallest finger stretched out, with your arm extended. Saros136 (talk) 04:14, 14 September 2014 (UTC)

Take a look at:

Mercury is presently visible in the evening sky, but only for observers in southern latitudes. mainly the Southern Hemisphere. As is explained in this WP article, folks down there can often see Mercury better than those of us who live in north-temperate latitudes.
DOwenWilliams (talk) 02:13, 15 September 2014 (UTC)
Thanks but I'll have to let another observation confirm or disconfirm this belief. There's ambiguity as to whether Chicago would count as mid latitude. I'll probably be in Chicago today at sunset, this will be the perfect excuse I need to get to the John Hancock observatory at sunset. It should be cloudless. I've been thinking...I saw it on a day the the Sun was obscured by clouds so there was less scattered light.

Saros136 (talk) 14:26, 17 September 2014 (UTC)

Let us know if you see it, with naked eyes, of course. A good telescope would almost certainly let you see it.
I once saw Mercury purely by chance, without looking for it, while I was driving my car here in Toronto, which is only a degree or two north of Chicago. It was soon after sunset, and I was driving westward. I noticed a bright "spark" low in the sky ahead of me. Having seen Mercury many times previously, I recognized it. When I got home, I checked that Mercury was in the right place. It was, so I am confident that I saw it. But that was near the March equinox, when Mercury can be much more easily seen from these latitudes than it ever is in September.
Good luck.
DOwenWilliams (talk) 15:10, 17 September 2014 (UTC)

Mercury's internal structure

Please consider revising the paragraph about Mercury's internal structure.

The most recent paper about the planet's interior (Smith et al., 2012, Science) assesses that Mercury's outer radius of the liquid portion of the core is ~2030 km, while there is no estimation for the inner solid component of the core. This means that, being the planet's radius ~2440 km, the total volume of Mercury's core is ~57% of the planet's volume. This percentage is much larger than the previously estimated 42%.

Being the core 2030 km, the outer silicate shell (mantle + crust) automatically gains a ~410 km nominal thickness, though this might be thinner if we consider an hypothetical FeS layer at the base of the silicate shell ranging from few tens of kilometers to ~200 km (Smith et al., 2012). This layer is the authors hypothesis to explain the high bulk density of Mercury's solid outer shell, which is in contrast with the low Fe abundances detected on Mercury's surface.

In the same paper a crustal thickness ranging from 20 to 80 km is also estimated.

Thus, considering the layers upper limits, the new internal structure would be:

20-80 km -- CRUST

80 - 210 km -- MANTLE

210 - 410 km -- FeS layer (hypothetical)

410 - 2440 km -- CORE (liquid+solid)

I am not an english native speaker and cannot directly contribute to the article, but I hope you can use this information anyway.

Vale (talk) 18:53, 4 November 2014 (UTC)

All local planets should make some mention to the Antikythera mechanism

The existence of the Antikythera mechanism shows that Mercury and other planets were already well understood at around 100BC. I think this is of quite historical significants, and thus a sentence about this should be at least be mentioned under the historical heading of these planets. — Preceding unsigned comment added by (talk) 10:47, 6 November 2014 (UTC)


The URL/name of this Mercury page includes “planet” in parentheses. It is the only one of the sun’s planets (+ Pluto, don’t do that argument here) having this parenthetical qualifier. Is there a powerful reason why Mercury should be so distinguished? JDAWiseman (talk) 14:14, 21 November 2014 (UTC)

Basically, there are 3 or 4 notable Mercury's on Wikipedia. -- Kheider (talk) 14:28, 21 November 2014 (UTC)
Agreed. But the same is true of most of the planets. JDAWiseman (talk) 20:42, 21 November 2014 (UTC)
Not quite: There is the element, which is not the case for any of the others. --JorisvS (talk) 20:59, 21 November 2014 (UTC)
The element mercury appears to be the only article among the chemical elements that has parentheses in the title as well. --Patteroast (talk) 21:02, 21 November 2014 (UTC)
Yes, the element clashes with the planet as the primary topic and vice-versa. --JorisvS (talk) 21:05, 21 November 2014 (UTC)
Clearly the consensus is happier than am I with the seeming inconsistency. In so far as this was construed as a suggestion, that suggestion is withdrawn. JDAWiseman (talk) 10:36, 24 November 2014 (UTC)

Image of mercury's place in the Solar System

Wouldn't it be nice to have the image of all the planets in the solar system, that's currently only in a hidden template at the bottom, on a more prominent spot? I think it's the most informative picture. One could argue that that's an image of the solar system, so it should only be shown there. But i think that many users will come to this page to look up where Mercury was in the order of planets and how big it is. It's either being technically correct, or supporting the information that people actually come to this page for with a nice image. I'm sure someone will say it's against this or that policy or something, but let's not forget the purpose of wikipedia: providing the information people come for. At the very least we should leave the template box open imho. PizzaMan (♨♨) 20:35, 30 November 2014 (UTC)

Something like that sounds more appropriate at Solar System. As required, the first lead sentence says that Mercury is the planet closest to the Sun. --JorisvS (talk) 11:30, 1 December 2014 (UTC)
The mean radius of Neptune's orbit is about 80 times Mercury's. Showing them both to scale on a diagram would be difficult. If the radius of Neptune's orbit were shown as the width of the screen, the radius of Mercury's orbit would span only the width of a couple of letters. Putting the name of the planet in this tiny space would make it illegible. DOwenWilliams (talk) 22:24, 1 December 2014 (UTC)
I was talking about planet sizes and relative order, not about showing orbit distance to schale. PizzaMan (♨♨) 11:42, 3 December 2014 (UTC)
Another issue to consider is consistency. The image you speak of belongs to a navigation box that is at the bottom of (every?) other article(s) dealing with members of the solar system. If you were to display the navbox more prominently, it would be inconsistent, or, if you're only talking about the image, would make the navbox image redundant. I think the way the article is now, with a link to the Solar System article up front, as well as making clear Mercury's size and closeness to the sun, should be enough for anyone who realizes he or she wants a quick overview of the entire system, but who isn't yet aware of the availability of the navbox. Dhtwiki (talk) 12:31, 3 December 2014 (UTC)
I see the potential disadvantages. Perhaps it's best to only leave the solar system infobox open by default. And of course do that for all planets.PizzaMan (♨♨) 15:11, 3 December 2014 (UTC)
This image:
shows the sizes of planets to scale. Maybe a link to it should be put in the "see also" section of every relevant article. DOwenWilliams (talk) 23:12, 3 December 2014 (UTC)
That is the image at the Solar System system article, undermining the goal of making every See Also link not be redundant to in-body links and References. It's also an inferior image to the one in the Navbox, which OP likes, but which I think is available enough (the Navbox is at Solar System, too), once people get to know how these articles work, and then start to value consistency and lack of redundancy, as well. Dhtwiki (talk) 22:41, 4 December 2014 (UTC)
That's a beautiful image, DOwenWilliams. The one in the navbox has a major advantage though. It's already there. It's also clickable for each planet. I agree articles shouldn't be too redundant, but a little redundancy can serve the purpose of quickly helping WP users to the info they want. So how about just setting the infobox open by default? That would be a relatively small change, easily done in all planet articles for consistency.PizzaMan (♨♨) 16:52, 5 December 2014 (UTC)
But this article is just the wrong place for a more explicit image of the planets of the Solar System, because this article is about Mercury, not the Solar System. --JorisvS (talk) 16:57, 5 December 2014 (UTC)
I don't agree per the arguments given above. PizzaMan (♨♨) 00:14, 7 December 2014 (UTC)
Meaning precisely what? --JorisvS (talk) 11:11, 7 December 2014 (UTC)
A certain degree of overlap in articles discussing overlapping topics is desirable. As i stated above, i think the image of mercury's size and position relative to other planets is the most informative image one could find on a page about mercury. Technically it's an image of the solar system and should therefor be placed on that page. But what's wrong with providing a little context and delivering information (both in text and images) that people actually come to this page for? I've once had two lectures about a difficult topic. One was by a brilliant professor who was completely technically correct and immediately went into all possible exceptions and avoided any simplifications and, importantly, any redundancy. The other one was actually understood by the audience. PizzaMan (♨♨) 21:31, 7 December 2014 (UTC)

────────────────────────────────────────────────────────────────────────────────────────────────────{I've lost count of colons.) I've added one short line to the "see also" section. It's a link to the diagram of the sizes of all the planets that I mentioned above. Is there any reason why this little line should not also be put into all the other planets' articles? It leads to information that many readers may be seeking, without using much space. DOwenWilliams (talk) 22:06, 7 December 2014 (UTC)

Perhaps it would be even better to expand the infobox by default so users don't even have to click to see such an image. But one wouldn't exclude the other per se. PizzaMan (♨♨) 00:59, 8 December 2014 (UTC)
Is that diagram drawn to scale? Is its scale better than the Navbox image, which includes Pluto and other dwarf planets? The See Also addition you made is redundant, unless it shows to better scale, and redundancy in a written reference is different from that in an oral presentation. I think it would be useful to have a discussion at Wikiproject Astronomy or Solar System, before making changes to other articles. Dhtwiki (talk) 01:08, 8 December 2014 (UTC)
That's a good idea. Would you mind starting that discussion and placing a link here?PizzaMan (♨♨) 23:03, 8 December 2014 (UTC)
I'm not the one who wants to change things. I just think that if you want to change more than this article, the discussion should range more widely than just this article Talk page. (By the way, I'm signing your comment above, by copying your signature from below User:JorisvS.) Dhtwiki (talk) 06:44, 9 December 2014 (UTC)
Redundancy should be natural: Because something about either topic would be missing if not presented on both pages. A size comparison with Earth and the Moon would be good (I think would be better/clearer than the current size comparison of the four terrestrial planets). --JorisvS (talk) 10:47, 8 December 2014 (UTC)
I totally agree. Note that in the image about planets in the infobox, the moon is also visible and to scale, but that's only a few pixels. So i think at least adding the moon to the image at the bottom of the page would be a good idea. And expanding the infobox to show the relative place of mercury.PizzaMan (♨♨) 23:03, 8 December 2014 (UTC)
Redundancy should be labeled as such, then. The See Also image (is it to scale?; it's not labeled as such, but could well be) should be labeled as the same one appearing at the Solar System page (that's obvious from the link, I suppose, but here some redundancy labeling might be helpful). There is an image at Commons that shows Mercury and the Moon, as well as Mars, Pluto, and Haumea. Adding it, if only to balance the other image under Comparison, might be helpful. However, I don't see the need to have the Navbox open, still.
Left to right, back to front: Mars, Mercury, the Moon, Pluto, Haumea
Dhtwiki (talk) 07:52, 9 December 2014 (UTC)
Have gone ahead and added image, as there was quite a bit to it. It can be reverted if unwanted. Dhtwiki (talk) 09:20, 9 December 2014 (UTC)
I'd consider the best comparison(s) something like [8] or [9], especially the former, but of course with Mercury (included) (which does not currently exist). Maybe I'll make a Mercury version of the former later. --JorisvS (talk) 11:30, 9 December 2014 (UTC)
Adding the image definitely helps a lot in terms of visualizing the relatice size of mercury. However, one of the most important facts about mercury and the other planets in the solar system is their relative position. I think it's elegant to visualize the most important points in a WP article. PizzaMan (♨♨) 16:02, 11 December 2014 (UTC)

Semi-protected edit request on 29 January 2015

Please replace

| moment_of_inertia_factor = 0.346±0.014


| moment_of_inertia_factor = 0.346±0.014 [1]

because the current value is unsourced.

Please replace

| axial_tilt = 2.11′ ± 0.1′[2]


| axial_tilt = 2.04′ ± 0.08′[1]

because the current value is obsolete.


Thank you.


  1. ^ a b c Margot, Jean-Luc; Peale, Stanton J.; Solomon, Sean C.; Hauck, Steven A.; Ghigo, Frank D.; Jurgens, Raymond F.; Yseboodt, Marie; Giorgini, Jon D.; Padovan, Sebastiano; Campbell, Donald B. (2012). "Mercury's moment of inertia from spin and gravity data". Journal of Geophysical Research: Planets. 117 (E12). Bibcode:2012JGRE..117.0L09M. doi:10.1029/2012JE004161. ISSN 0148-0227. 
  2. ^ Cite error: The named reference Margot2007 was invoked but never defined (see the help page). (talk) 02:53, 29 January 2015 (UTC)

Yes check.svg Done  B E C K Y S A Y L E 05:21, 29 January 2015 (UTC)

Linking metallic

I agree that normally, making the word "metallic" into a link to Metal is silly and unnecessary. However, in this situation (Mercury consists of approximately 70% metallic and 30% silicate material.), "metallic" is being used in a technical chemical sense that requires clarification for the layman, not in the common sense. Some things that seem metallic in the common sense are not chemically metallic, and some things that do not seem metallic in the common sense are, in fact, metallic. So, IMO, the common word "metallic" should be linked to Metal here, since it is being used in a technical rather than common way. Thoughts? A2soup (talk) 01:03, 13 March 2015 (UTC)

Disagree. No clarification is needed here. The average reader knows there are lots of types of metal and doesn't need to read an article about metals to understand the one sentence here. Metal is a common-enough word not to need explaining here in any detail. If it would be useful to know the types of metal involved, we can be told here instead (with specific, rather than general, links). Silicate is an uncommon term and needs a link. (As it happens, another reason to avoid a link to metal is that it currently takes the reader to an article which says in its lead that in astronomy everything is "metal" apart from hydrogen and helium - as silicates are neither hydrogen nor helium, what is the poor reader to make of that claim?) BencherliteTalk 01:12, 13 March 2015 (UTC)
I mildly disagree with your initial arguments, but very much agree with your last. On the balance, you are correct that it is more confusing to link metal than to not link it here. Thanks for pointing out the confusing statement in the Metal lead! A2soup (talk) 01:25, 13 March 2015 (UTC)
Isn't "metal" in this context kind of 'stuff heavier than rock'? --JorisvS (talk) 10:59, 13 March 2015 (UTC)

Semi-protected edit request on 31 March 2015

Under heading Magnetic Field and Magnetosphere.

Please change the sentence

   According to measurements taken by Mariner 10, it is about 1.1% as strong as Earth's.


   According to measurements taken by Mariner 10, it is about 1.1% the strength of Earth's.

Because I feel it is more readable. (talk) 11:37, 31 March 2015 (UTC)

Yes check.svg Done Kharkiv07Talk 17:02, 31 March 2015 (UTC)

Dark surface caused by carbon accumulation

"Mercury 'painted black' by passing comets"

"Darkening of Mercury’s surface by cometary carbon"

BatteryIncluded (talk) 02:15, 31 March 2015 (UTC)

Would the carbon make Mercury's surface electrically conductive? If so, would electric currents in it be related to the magnetic field? DOwenWilliams (talk) 02:38, 3 April 2015 (UTC)


Article had incorrect phrase, "was crashed into Mercury", which translates as, "Mission controllers used thrusters on the spacecraft to change its orbit so that it would crash into the surface." But that was not the case. Mission controllers did everything they possibly could to prevent the crash, including using the helium, which pressurized the fuel, as a propellent.[1] Before approval, early in the mission design phase, it was understood that the spacecraft would crash into the surface of Mercury. They knew there was no way to design the mission to avoid this fate. They also knew that the human mission controllers would not need to do anything to make this outcome happen. In the event the mission was extended 3 years past the planned 1 year, and all of the control fuel was used up. At that point the Sun's massive gravity perturbed the Messenger orbit enough to cause it to crash. As said above they even used the pressurization gas as a "fuel" to extend the mission one extra day.[1] Nick Beeson (talk) 22:37, 30 April 2015 (UTC)


Semi-protected edit request on 27 July 2015

in the box on the right, replace "greyscale" with "grayscale" BGS (talk) 10:09, 27 July 2015 (UTC)

X mark.svg Not done - greyscale is a perfectly good spelling - Arjayay (talk) 10:57, 27 July 2015 (UTC)

Better banner image?

This image is in true colour, rather than greyscale, and I think it is more informative. Serendipodous 18:33, 3 September 2015 (UTC)

I prefer color images, too. The downside is that it is of lower resolution, although I don't think that is a problem in this case. --JorisvS (talk) 20:37, 3 September 2015 (UTC)

File:Mercury in color - Prockter07-edit1.jpg to appear as POTD

Hello! This is a note to let the editors of this article know that File:Mercury in color - Prockter07-edit1.jpg will be appearing as picture of the day on January 13, 2016. You can view and edit the POTD blurb at Template:POTD/2016-01-13. If this article needs any attention or maintenance, it would be preferable if that could be done before its appearance on the Main Page. Thanks! — Chris Woodrich (talk) 01:09, 25 December 2015 (UTC)

Picture of the day
Mercury (planet)

Mercury is the smallest and closest to the Sun of the eight planets in the Solar System. It has no known natural satellites. The planet is named after the Roman deity Mercury, the messenger to the gods.

Photograph: NASA/APL/CIS; edit: Jjron
ArchiveMore featured pictures...

Possible Math Mistake in "Advance of Perihelion"

Quote from article:

"The perihelion precession of Mercury is 5600 arcseconds (1.5556°) per century relative to Earth, or 574.10±0.65 arcseconds per century[96] relative to the inertial ICFR. Newtonian mechanics, taking into account all the effects from the other planets, predicts a precession of 5557 arcseconds (1.5436°) per century.[96] In the early 20th century, Albert Einstein's general theory of relativity provided the explanation for the observed precession. The effect is small: just 42.98 arcseconds per century for Mercury"

Is there a mistake here, or has there been a new discovery in the past few years?

I remember hearing on a television special (History or Science or some such,) that the precession of Mercury is in fact not entirely explained by Relativity, and that there is still an unknown influence on Mercury causing it to precess. This detail is not mentioned in this section of this article, though it definitely should be.

Also suggest mention and references of how alternate calculations were done before relativity. It helps to know what "wrong" or "insufficient" calculation have been tried in the past.

In other words, why isn't the best previous Newtonian calculation actually shown, and then actually show the best Relativity calculation.

This is relevant, because I have anomaly...and want to mention it in a paper.

WadeDanielSmith (talk) 00:11, 2 November 2015 (UTC)

Information this detailed is probably better suited for Tests_of_general_relativity#Perihelion_precession_of_Mercury. A2soup (talk) 02:13, 25 December 2015 (UTC)

Mercury's atmosphere <~5 x 10-15 bar

I've added the info to the article where appropriate. Thanks for the suggestion! A2soup (talk) 16:12, 27 January 2016 (UTC)

Tidally locked or not

I'm new to this whole "edit" process, but I noticed a problem. It says Mercury is gravitationally locked. It should say that it is NOT gravitationally locked. Or better yet, tidally locked. Thanks. TDFmachine (talk) 14:45, 7 February 2016 (UTC)

Indeed, it's only 3:2 locked. See [1]


  1. ^ Elkins-Tanton, Linda T. (2006). Uranus, Neptune, Pluto, and the Outer Solar System. Infobase Publishing. p. 51. ISBN 978-1-4381-0729-5.  Extract of page 51
I made the change ([10]) in the article, and added the source. I also made a wp:wikilink to article Tidal locking. Good find. - DVdm (talk) 15:07, 7 February 2016 (UTC)

OK, So, I understand the cited book says [3:2] "resonance", but I can't figure out why this should be a Resonance; what seems to actually happen, if you watch Mercury from the Sun, is that Mercury's rotation follows the Sun **near perihelion** (very near Perihelion rotation actually lags behind orbit); far from perihelion, the tidal stress tends to slow Mercury's rotation, but near perihelion the tidal stress is about three times greater. The apparent ratio [3:2] isn't necessarily an integer ratio at all, but something that should be calculated from Mercury's eccentricity. NOW, whether one can **put that in the article**... one would have to hunt up an actual source. In any case, the cited work doesn't actually establish the claim. Jcmckeown (talk) 05:59, 9 March 2016 (UTC)

Near perihelion, when the tides are largest, they are almost stationary on Mercury, so they don't significantly slow down or speed up its rotation. As you say, this would be only an approximate situation, which would not lead to a precise 3:2 ratio. However, here is another factor. Even without tides, Mercury is not exactly spherical. It has a permanent bulge on one side. The rotation is such that at perihelion this bulge faces toward or away from the Sun. This couples to the tidal component of the Sun's gravity, which keeps this situation permanent. This locks the rotation of the planet to an exact 3:2 ratio with its orbital motion. DOwenWilliams (talk) 15:04, 9 March 2016 (UTC)

Requested move 7 April 2016

The following is a closed discussion of a requested move. Please do not modify it. Subsequent comments should be made in a new section on the talk page. Editors desiring to contest the closing decision should consider a move review. No further edits should be made to this section.

The result of the move request was: Closed WP:SNOW (non-admin closure) NottNott talk|contrib 09:27, 8 April 2016 (UTC) ~~~~

Mercury (planet)Mercury – This is a level-3 vital article, while the element is a level-4 vital article. Thus, this should take precedence. Sir Cumference π 19:01, 7 April 2016 (UTC)

  • Oppose. That's not how determining primary topics works. I could elaborate, but as I don't expect this will get much traction, I'll just leave it at this for now. Egsan Bacon (talk) 19:30, 7 April 2016 (UTC)
  • Support. The levels have nothing to do with it. But the planet is currently 50.3 percent of pageviews (499,133/991,696). See here. Brother Twisted (talk) 03:39, 8 April 2016 (UTC)
  • Strong oppose the element is much more common in the daily life of most people than the planet. The god is also not uncommon in ordinary life. And I can't see why you'd want to delete the disambiguation page and merge it into a hatnote onto this article. -- (talk) 05:02, 8 April 2016 (UTC)
  • Oppose - Pageviews shows this article and Mercury (element) as essentially equal. Google returns twice as many results for the element than for the planet. Historically and scientifically, neither is the primary topic. The current setup with a dab page is the correct one. A2soup (talk) 05:12, 8 April 2016 (UTC)
  • Oppose. Leaving "Mercury" as a disambiguation page is the best option. Huntster (t @ c) 05:13, 8 April 2016 (UTC)
  • Strong oppose. The planet is less often referred to in everyday life, compared to to the chemical element. Reify-tech (talk) 05:21, 8 April 2016 (UTC)
  • Strong oppose. Neither the element nor the planet are clearly the primary topic, so the status quo should be maintained. Double sharp (talk) 05:39, 8 April 2016 (UTC)
  • Strong oppose, the current title is wrt to all mentioned criteria of naming conventions superior to the suggested alternative. I'd propose to include a hatnote referring back to the disambiguation in both articles, serves afficionados of both. Purgy (talk) 05:53, 8 April 2016 (UTC)
  • Oppose. On a fine, warm (northern) spring day, me thinks I detect an unseasonable snowball. YBG (talk) 07:03, 8 April 2016 (UTC)
  • Oppose. The metal is far more common than the planet: Google Scholar "mercury planet" (1,570 hits) vs Google Scholar "mercury metal" (5,220 hits) and Google Books "mercury planet" (7,460 hits) vs Google Books "mercury metal" (23.000 hits). - DVdm (talk) 07:16, 8 April 2016 (UTC)

The above discussion is preserved as an archive of a requested move. Please do not modify it. Subsequent comments should be made in a new section on this talk page or in a move review. No further edits should be made to this section.

Correcting outdated information.

Dear Admin,

I see that the section 'Spin–orbit resonance' provides outdated information.

Specifically, the sentence

"This is thought to explain Mercury's 3:2 spin–orbit resonance (rather than the more usual 1:1), because this state is more likely to arise during a period of high eccentricity. [93]"

should be changed to:

"This was thought to explain Mercury's 3:2 spin–orbit resonance (rather than the more usual 1:1), because this state is more likely to arise during a period of high eccentricity. [93] However, accurate modeling based on a realistic model of tidal response has demonstrated that Mercury was captured into the 3:2 spin-orbit state at a very early stage of its history, within 20 (more likely, 10) mln yr after its formation. [169]"

169. Noyelles, Benoit; Frouard, Julien; Makarov, Valeri; and Efroimsky, Michael. (2014) "Spin-orbit evolution of Mercury revisited." Icarus, Vol. 241, pp. 26 - 44 Bibcode:2014Icar..241...26N DOI: 10.1016/j.icarus.2014.05.045

Many thanks,

Michael Efroimsky Astronomer US Naval Observatory Washington DC 20392

Efroimsk (talk) 21:32, 22 April 2016 (UTC)