Talk:Deimos (moon)

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So, what kind ice does Deimos have, with a surface temperature of "~313 K" (a very hot summer day where I live)? Gene Nygaard 19:45, 5 Jan 2005 (UTC)

The ice mentioned is inside Deimos. Because of its low albedo (0.07), a steadily illuminated Deimos surface would reach equilibrium at ~313 K. With rotation and shadowing, one would expect the average temperature to be somewhat lower. The interior could contain a lot of ice, protected by the insulating dark crust. Just a guess. Do we have any actual surface temperature measurements quoted anywhere?
Urhixidur 03:45, 2005 Jan 6 (UTC)


The article had DAY-mus. This is an attempt at the classical Greek pronunciation; the English equivalent is DYE-mus or perhaps DEE-mus. Most refs, including Geyley's 1893 (1911, 1939) Classic Myths in English Literature and in Art and Zimmerman's 1964 Dictionary of Classical Mythology have the former; a few, such as Tripp's Meridian Handbook of Classical Mythology have the latter.

The Greek is the same as in dinosaur (just substitute N for M), if that helps you decide on a pronunciation. (Deinothere has the same vowel spelling in English as Deimos as well; it's also pronounced DYE-.) —kwami 07:44, 7 Apr 2005 (UTC)

Added the Greek spelling, which will provide the DAY-mus pronunciation to anyone who wants to be 'authentic'. --kwami 01:11, 11 Apr 2005 (UTC)
Anyone know of an adjectival form? I can't find anything. I assume something like Deimian would be acceptable, but don't know if anything else is in use. kwami 2005 June 30 06:22 (UTC)

It is related to dinosaur; it is not the same. But the first syllable should pronounced the same way. Septentrionalis PMAnderson 17:06, 3 June 2007 (UTC)

Am I really the only one who pronounces it "DAY-mohs"? It's the closest to the Greek pronunciation and most closely follows the spelling. (talk) 17:42, 24 October 2014 (UTC)

Orbital evolution[edit]

Anybody know of good info on the orbital evolution of Deimos? Since it's higher than synchronous orbit, it is moving outward, and I believe it will eventually escape; but I haven't found any good refs for the time scale required. --Reuben 21:05, 4 April 2007 (UTC)

Density discrepancy[edit]

The current listed density (2.2 g/cm3) (unreferenced) differs significantly from these 2 NASA data pages:

Therefore, I decide to change it to the JPL value (that page is better referenced), and adding a reference to that page. Regards, --Dna-Dennis (talk) 21:33, 29 January 2008 (UTC)

Appearance of Mars from Deimos[edit]

The figures comparing the appearance of mars from Deimos to that of the full moon from earth are calculable from almanac data. The apparent radius of mars is given by arcsin ( Rmars / Rorbit ), giving 0.145 radians or 8.3 degrees . 90/8.3 = 10.8 gives the "one-eleventh" figure cited as the fraction of the width of the celestial hemisphere (i.e. 180 degrees ) taken up by the martian apparent diameter.

The apparent radius of the moon from the earth varies, and brackets the value of 0.00457 radians required to give the "1,000 times larger" comparison for mars' appearance from Deimos.

The intensity of lunar and martian sunlight also vary, and the minimum and maximum ratios bracket the value of 2.5 required to justify the "400 times brighter" comparison, assuming equal albedos. The albedo of the full moon approaches that of mars, but may be somewhat less, so a figure as high as "500 times" is perhaps justifiable, although the question is probably moot for a comparison of this type.--L mammel (talk) 01:30, 16 April 2008 (UTC)

Please correct me if I'm wrong but I'm seeing a contradiction in your explanation of the "one-eleventh" figure. Dividing 90/8.3 should yield the fraction Mars takes up of one half of the sky. 180/8.3 (21.6) would be the entire celestial hemisphere, because just as you say, it is 180 degrees across. (talk) 17:04, 16 April 2008 (UTC)
Note that 8.3 degrees is the apparent radius of mars, and 90/radius = 180/diameter . I guess I kind of snuck that one in, but it's there!--L mammel (talk) 22:17, 16 April 2008 (UTC)


Deimos is "the outer & smaller" of Mars' mini-moons. Thus, Mars' mini-moons decrease in mass outwards radially — completely consistent, along w/ their circular & equatorial orbits, w/ them having formed in situ from the same disk of dusty debris that made up Mars in the middle. -- (talk) 13:39, 7 March 2010 (UTC)

Though the moons do decrease in mass outwards, a sample size of 2 is not very convincing. Keep in mind that Jupiter's inner spherical moons Io and Europa (4.80×1022) are less massive than the outer spherical moons Ganymede and Callisto (1×1023). -- Kheider (talk) 19:13, 7 March 2010 (UTC)

calendar conventions[edit]

... given in contemporary sources as "August 11 14:40" Washington mean time using the old astronomical convention of beginning a day at noon ...

Roadrunner changed "the old" to "an", saying, Not an old convention - see Julian Day.

Yes, the Julian Day still counts from noon, but "August 11" is not a JD number. Does anyone still treat August 11 as beginning at local noon? If not, why not call that an "old" convention? —Tamfang (talk) 19:50, 21 August 2010 (UTC)


If I'm not wrong, there is an error in the value of the orbital inclination to Mars' equator. In fact, the cited source reports an orbital inclination of 1.7878° (positive) to the local Laplace plane, whose inclination is 0.8886° (positive) to Mars' equator. So, this two values should be summed and not subtracted. The correct value should be of 2.6738° to Mars' equator. --Harlock81 (talk) 00:08, 26 March 2012 (UTC)

What does "positive" mean in this context? Knowing the inclination leaves one degree of freedom; without that other number you can't simply add inclinations. —Tamfang (talk) 15:26, 7 April 2012 (UTC)
Well, that's not true. Both values are positive in the same table, so they are positive according to the same reference system adopted for compile the table, and consequently they should be summed. While your answer is not a real answer, because you have not explain why they should be subtracted, as done in the present article. --Harlock81 (talk) 22:07, 14 April 2012 (UTC)

Deimos template map[edit]

FWIW - added a newly created {{DeimosCraterNames}} imagemap template to the article - tried to label the crater locations as best as possible at the moment - (labels can be hyperlinked to relevant articles, like the label for Voltaire (crater)) - locations are "best-guesses" - a labeled Deimos image seemed helpful - any further help with this template project would be welcome of course - in any case - Enjoy! :) Drbogdan (talk) 17:42, 19 August 2013 (UTC)

Lockheed Martin "Red Rocks" mission[edit]

I think this article - and the Phobos one - under exploration should probably mention the Lockheed-Martin "Stepping Stones to Mars" "Red Rocks" study of possibilities and advantages of human exploration of Phobos and Deimos and their use as a base for telepresence exploration of Mars itself.



What do you think? Robert Walker (talk) 12:47, 14 September 2015 (UTC)

That seems fine with me Robert though I feel that the entire Exploration section needs a bit of cleanup. Some mission names are italicized while others are not. Some paragraphs do not mention who made the proposals and when they did so, when the mission would run, who would sponsor it, etc. --Marc Kupper|talk 19:19, 16 February 2016 (UTC)
Sorry for the delay in my reply, only just noticed that you responded. Okay I'll take a look some time. Just adding a note with a link to a paper with a detailed discussion of Phobos and Deimos as exploration targets to summarize here done in connection with the Red Rocks design [1] Robert Walker (talk) 01:12, 21 March 2017 (UTC)

Appearance of Deimos from Mars[edit]

The article says that Deimos' rotation is synchronous but does not say or show which face is always pointed towards Mars. For example, are the craters Swift and Voltaire on the "face" of Deimos', off to the side, or on its back relative to Mars? --Marc Kupper|talk 19:11, 16 February 2016 (UTC)

Inadequate refs[edit]

The "HORIZONS Web-Interface" reference (ref name=Horizons), reference #1, cited in full in the "semimajor" parameter in the infobox, is not a full citation at all. The link goes only to the home page of this web interface resource, which begins

The JPL HORIZONS on-line solar system data and ephemeris computation service provides access to key solar system data and flexible production of highly accurate ephemerides for solar system objects ( 726050 asteroids, 3445 comets, 178 planetary satellites, 8 planets, the Sun, L1, L2, select spacecraft, and system barycenters ). HORIZONS is provided by the Solar System Dynamics Group of the Jet Propulsion Laboratory.

That page says nothing about Deimos or any other body in the Solar System, and the search is not particularly easy. The article references it seven times, probably many of them at different locations. These should be made more precise. --Thnidu (talk) 05:56, 25 January 2017 (UTC)