# Talk:Atmosphere of Venus

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## References &c.

I made some minor changes to references; I also deleted a sentence that mentioned the albedo of Venus is 0.76, since one sentence later it stated that Venus reflected 90% of the incident sunlight. The alternative to deleting this sentence would have been a long discussion of the different types of albedo (which varies with wavelength), which would have been rather off topic; people actuallly interested in albedo can look at the albedo entry.

Geoffrey.landis 15:13, 12 September 2006 (UTC)Geoff Landis

## hydrogen can easily be extracted

"Hydrogen is primarily present as sulfuric acid (H2SO4), and hydrogen can easily be extracted through condensing the droplets."

Sulfuric acid does not release any hydrogen by "condensing" the droplets. On the contrary, sulfuric acid attracts and holds any water violently. Perhaps this is the reason why there is any trace of water on Venus left at all. 84.160.239.47 22:17, 17 November 2006 (UTC)

Fixed. --Xanthine 12:30, 3 January 2007 (UTC)

The article has several apparent contradictions which need to be explained in footnotes if not the main text ie "sulpher dioxide is 150 parts per million." No mention of sulpher trioxide which should be in surplus if there is "no water." It says 6 parts per million of water vapor in another part of the article. I suppose the problem is the composition of Earth's atmosphere is typically given as gas only and particulates such as dust, sulpheric acid, ice and water droplets are discussed separately. Also, Earth atmosphere scientists typically include the carbon dioxide vapor percentage, but not the water vapor percentage; just the opposite of how we have figured Venus, perhaps because the lower atmosphere of Venus is hot enough that carbon dioxide is a gas, not a vapor, as it is in Earth's atmosphere. Neil

The text includes the conjecture that Venus' atmosphere is composed of largely carbon-dioxide and nitrogen mixture because of the lack of a strong magnetic field, lighter gases not being held because of the lack of a strong magnetic field as Earth has. That would hold true also for Mars, which has a largely carbon dioxide-nitrogen atmosphere (if much thinner).

A simpler explanation exists: Venus is hot. Magnetic fields do not hold gases so effectively as does gravity. The Earth has high enough gravitation and cooler temperatures to hold gases as light as methane, ammonia, and water vapor. To be sure, the Earth's atmosphere holds little methane or ammonia because of thermodynamic instability in an oxygen-rich environment, but it holds water vapor very well. It's, of course, gravitation. A strong magnetic field may prevent some chemical reactions in the Earth's upper atmosphere, preventing the formation of such substances as sulfuric acid, but that is a different topic.

Venus is much hotter at its surface, hot enough that with gravity slighter (but not by much!) than the Earth's, Venus cannot hold gases as light as methane, ammonia, and water vapor. Much chillier than Earth, but with far lesser gravity, Mars likewise cannot hold water vapor. With their combinations of temperature and gravitation, both Mars and Venus can hold atmospheres consisting largely of carbon dioxide and nitrogen. --Paul from Michigan 01:49, 25 November 2006 (UTC)

If proponents of Gaia theory are to be believed, a major reason for the water on Earth is due to the abundant presence of life. Indeed, all living things capable of aerobic respiration produce water as a matter of discourse. Venus and Mars, on the other hand, have atmospheres relatively close to their equilibrium states (Mars more so than Venus). Interestingly enough, Lovelock discusses this in the first of his Gaia books, calculating that if Earth were to be left to form an equilibrium state (ie: if all life were somehow wiped out), it's atmosphere would be ~95% carbon dioxide and it's surface temperature would be in the region of 250 centigrade. Makes you think, doesn't it...? --Xanthine 12:30, 3 January 2007 (UTC)

Life is of course a non-equilibrium state. Under equilibrium, water would react with carbon and carbon compounds to form carbon dioxide, and with sulfur and sulfur compounds to form sulfuric acid. As is well known one can place carbon and sulfur in cold water and have no reactions.

Biochemistry itself suggests that life formed on Earth from a mixture of substances, some of which would not exist long in an oxygen-rich environment. Of course, water, carbon oxides (whether carbon monoxide or carbon dioxide), and phosphates exist. But most biochemical substances are methane derivatives. Ammonia and hydrogen sulfide would have to have existed.

Living things (plants) can synthesize methane derivatives from carbon dioxide and water and can transform mitrites and nitrates into ammonia. Some bacteria 'fix' mitrogen. But that is life at work.

Most predictions of the future of the Earth suggest that as the sun becomes more luminous, that unless the Earth's orbit becomes adequately displaced from where it is now (I believe that if humanity or some intelligent successor is around, that creature is likely to force the Earth into orbitd progressively more distant from the sun as needed), the Earth will get hotter. The Earth is toward the warm end of the life zone, and when the normal temperature on Earth approaches 45C, life will be in big trouble. Much of the biomass will die and become fuel for spectacular forest and brush fires that will thrust more carbon dioxide into the atmosphere, accelerating global warming. Higher evaporation of water will have added another greenhouse gas -- water vapor -- into the atmosphere. Atom for atom, water vapor is an even more powerful greenhouse gas.

Around 70C, the 'wet greenhouse' effect that some say occurred early on Venus takes off, and the Earth's atmosphere itself takes on the characteristics of a pressure cooker. Meanwhile, the greater pressure of the atmosphere causes the atmospheric temperature to rise in accordance with the gas laws. The process accelerates as more of the waters of the sea evaporate into the atmosphere. Some water vapor goes to the upper atmosphere and some water molecules dissociate into oxygen and hydrogen, hydrogen going off into space. Until the seas are evaporated away, there's more water vapor available to replace the water dissociated into oxygen and water.

At 305 C, the critical temperature of water, liquid water no longer exists. By then, even if the Earth has gigantic clouds protecting the planet from sunlight, pressure alone creates hothouse conditions. (Venus is hot because of the pressure of its atmosphere -- not because of the intense sunlight that shines upon cloud layers that insulate the planet). Carbonate rocks dwxompose, releasing carbon dioxide, and pressures lead to temperatures high enough to melt surface rocks.

Gory, isn't it? The earth's atmosphere would be full of oxygen from dissociated water, carbon dioxide first from the budning of biomass and petroleum and then especially the release of it from carbonate rocks, sulfuric acid from the burning of sulfur and sulfur compounds, a little nitrogen, and some water vapor. The Earth could get even hotter than Venus is today -- hot enough to melt all rock surfaces. That's all long before the Sun flares off the atmosphere and beats down upon the exposed surface of the Earth.

That all depends upon the extinction of complex life. We might not have the means -- yet -- of altering the Earth's orbit. But humanity or whatever its successor at the time (advanced pigs?) will likely cherish life enough to get the Hell out of an infernal prospect. The Gaia effect got little chance on Venus or Mars. It may need some help a few hundred milliion years hence just to continue. Sure, this is speculation, and as such 'original research'... probably forgivable in a talk page. --Paul from Michigan 10:20, 14 January 2007 (UTC)

Surely speculation is the entire point of a talk page! :) I'd love to continue this conversation, but I fear it'll soon venture too far off topic... --Xanthine 12:57, 23 January 2007 (UTC)

The magnetic field doesn't hold in hydrogen, it shields a planet from solar wind that would slowly scrub the hydrogen away into space. To address your question about sulfur trioxide, I believe the UV-initiated reaction in the upper atmosphere is CO2 + SO2 -> CO + SO3. And then SO3 + H20 -> H2SO4. So there is not an excess of SO3, it recombines with carbon monoxide given the chance. DonPMitchell (talk) 03:55, 9 August 2008 (UTC)

Venus is hot because of the pressure of its atmosphere You have a source for this? Perhaps this is based on the ideal gas laws, in which case it is a misunderstanding. When you compress a gas, it will certainly heat up. But temperature and pressure are independent variables, i.e. you can have a gas under high pressure which also at a low temperature. Pressure cookers work by increasing the boiling point of water, which allows the creation of hotter steam than is otherwise possible. The food isn't heated by putting it under pressure. You might suppose that Venus is warm because it is closer to the sun and gets more solar radiation. But, no, the albedo of the clouds is so high that the radiation Venus receives is actually somewhat less than that of Earth. Volcanism must have something to do with the high surface temperature since virtually no sunlight reaches it. At the very high pressure that exists on the surface (92 bars), 30 cm of CO2 is enough to absorb almost all the IR. So there's a superblanket that keeps the surface warm, whatever originally warmed it. Kauffner (talk) 14:47, 7 January 2011 (UTC)

## How hot is Venus?

How much hotter is Venus than Earth?

It's a lot hotter if you compare surface temperatures to surface temperatures -- 288K to 750K. But, if you compare atmospheric temperatures at the same pressures, say at 1 Bar, the difference is a lot less dramatic. Earth's 1 Bar temperature is 288K while Venus' is 360K. If you also subtract out the extra temperature due to Venus having to shed more heat from solar radiation, the difference in atmosphere temperature is around 20 K -- a whole lot less than the almost 500 degree difference in surface temperatures.

This means that the extra heat at the surface is coming from adiabatic compression (extra pressure), not from extra solar radiation or greenhouse effect. I've written up an article explaining this more fully, and posted it at

http://www.whiteworld.com/technoland/stories-nonfic/2008-stories/Venus-temp.htm

Cyreenik 15:31, 12 April 2007 (UTC)

Venus is so immensely hot, that a cat on a hot tin roof would stay on the roof, if it just knew how lucky it was. Said: Rursus 08:37, 29 November 2007 (UTC)
35 km above Venus's surface, the temperature is as hot as a typical baking or cooking oven. (See your cookbooks, if you're in America, there'll probably be quite a few references to 350 degrees Fahrenheit, which translates into 177 degrees Celsius, or 450 Kelvin. I dunno what it's like in other countries.)68.36.214.143 (talk) 00:12, 10 December 2007 (UTC)

## Good article nomination

• "Looks good" to me, except the last images at the bottom illustrating future missions need to be better sourced. One just says "from NASA", the other says "from university, presumably copied from NASA." Potatoswatter (talk) 21:53, 10 April 2008 (UTC)
I added a direct link to NASA site for the first image. I temporally removed the second one because I can not find it on the NASA server. Ruslik (talk) 05:58, 11 April 2008 (UTC)

## Survey

WP:Good article usage is a survey of the language and style of Wikipedia editors in articles being reviewed for Good article nomination. It will help make the experience of writing Good Articles as non-threatening and satisfying as possible if all the participating editors would take a moment to answer a few questions for us, in this section please. The survey will end on April 30.

• No. This article has had many contributors of varying English expertise; the path to clarity is clear. Potatoswatter (talk) 17:07, 12 April 2008 (UTC)
• If you write a lot outside of Wikipedia, what kind of writing do you do?
• Is your writing style influenced by any particular WikiProject or other group on Wikipedia?

At any point during this review, let us know if we recommend any edits, including markup, punctuation and language, that you feel don't fit with your writing style. Thanks for your time. - Dan Dank55 (talk) 21:05, 11 April 2008 (UTC)

## GA review

I've signed up to review this, and I'll put comments when I get a chance for a thorough read Jimfbleak (talk) 11:05, 29 April 2008 (UTC)

• Intro: see Wikipedia:Lead section. The lead seems the weakest part of the article. It should not exceed four paras, and the current fifth para is just one sentence. The lead gives too much detail in some places (eg percentage of atm. gases), but doesn't mention some of the main headings at all. Intro needs a bit of work. Jimfbleak (talk) 11:19, 29 April 2008 (UTC)
I made a few changes in the lead section. Ruslik (talk) 11:40, 29 April 2008 (UTC)
• Consistency and formatting. Careful copy edit is needed
1. Venusian should be capitalised. Venus' or Venus's? both are used, inconsistent
Fixed. Ruslik (talk) 07:41, 30 April 2008 (UTC)
1. units wander at random, eg K OC, sometimes both, also km/kilometres, shouldn't use both - I think it should be km
Fixed. Ruslik (talk) 07:41, 30 April 2008 (UTC)
1. I note that there are no conversions to imperial, is there a justification for this?
It was decided some time ago not to use them in the planetary articles. Ruslik (talk) 07:41, 30 April 2008 (UTC)
1.  % or percent, not both
Fixed. Ruslik (talk) 07:41, 30 April 2008 (UTC)
1. it is, not it's
Fixed. Ruslik (talk) 07:41, 30 April 2008 (UTC)
1. I would italicise in situ, is form used correct?
I would not because in NASA pages it is written without italicisation (Venus in Situ Explorer). Ruslik (talk) 07:41, 30 April 2008 (UTC)
1. refs should follow punctuation, some are in front of or not next to punctuation
Fixed. Ruslik (talk) 07:41, 30 April 2008 (UTC)
1. I've not gone through in detail yet, but in the "composition" section "D" as in D/H ratio appears out of the blue, no gloss or link to deuterium
Fixed. Ruslik (talk) 07:41, 30 April 2008 (UTC)
1. not a big deal, but would the green timeline look better centred? Also a lot of white space above it in my machine.
Removed. Ruslik (talk) 07:41, 30 April 2008 (UTC)
I'll go through in detail, do refs, images etc when i next get time. Jimfbleak (talk) 15:40, 29 April 2008 (UTC)
• references
1. ref 3 appears to be dead
Fixed. Ruslik (talk) 07:41, 30 April 2008 (UTC)
1. At FA (not GA) you will now have to write journal names in full. However, you do need to have spaces between the abbreviated forms (refs 1 and 8 at least)
Fixed. Ruslik (talk) 07:41, 30 April 2008 (UTC)
1. ref 10, need isbn 10, not 13, otherwise link doesn't work
Fixed. Ruslik (talk) 07:41, 30 April 2008 (UTC)
1. ref 18, stray ]
Fixed. Ruslik (talk) 07:41, 30 April 2008 (UTC)
Fixed. Ruslik (talk) 07:41, 30 April 2008 (UTC)
1. ref 27 appears to be dead
Fixed. Ruslik (talk) 07:41, 30 April 2008 (UTC)
1. ref 33 linkspam, no link would be better than to a commercial sales site
Fixed. Ruslik (talk) 07:41, 30 April 2008 (UTC)
1. ref 44 looks very strange, Vancouver WA? also appears to be dead
Fixed. Ruslik (talk) 07:41, 30 April 2008 (UTC)

Jimfbleak (talk) 16:05, 29 April 2008 (UTC)

Jimfbleak (talk) 16:05, 29 April 2008 (UTC)
• final read through: I’ve done some minor fixes, the following still need attention.
1. Intro: and the rise of the levels of greenhouse gases that followed clunky
Fixed. Ruslik (talk) 07:41, 30 April 2008 (UTC)
1. Composition: including some based on hydrogen, such as hydrogen chloride (HCl) and hydrogen fluoride (HF), nitrogen and sulfur, as well as the some carbon monoxide, water vapour and molecular oxygen Nitrogen and sulphur don’t contain hydrogen, “as well as the some”??
Fixed. Ruslik (talk) 07:41, 30 April 2008 (UTC)
1. Troposphere: The enormous amount of CO2 in the atmosphere together with water vapour and sulfur dioxide create a strong greenhouse effect, number agreement
There is no disagreement in my opinion. Ruslik (talk) 07:41, 30 April 2008 (UTC)
1. Upper atmosphere and ionosphere: The maximum electron volume density— Do we need an explanation of evd? Also no dash after quoted volume in this sentence
Fixed. Ruslik (talk) 07:41, 30 April 2008 (UTC)
1. Induced magnetosphere: The reason for its absence are not clear, number agreement. (0.3 Rv) no explanation of unit here
Fixed. Ruslik (talk) 07:41, 30 April 2008 (UTC)
I think that's all I can see now Jimfbleak (talk) 05:51, 30 April 2008 (UTC)
missed two "vapour", fixed now Jimfbleak (talk) 07:33, 30 April 2008 (UTC)

## Good Article assessment

GA review (see here for criteria)
1. It is reasonably well written.
a (prose): b (MoS):
2. It is factually accurate and verifiable.
a (references): b (citations to reliable sources): c (OR):
3. It is broad in its coverage.
a (major aspects): b (focused):
4. It follows the neutral point of view policy.
Fair representation without bias:
5. It is stable.
No edit wars etc.:
6. It is illustrated by images, where possible and appropriate.
a (images are tagged and non-free images have fair use rationales): b (appropriate use with suitable captions):
7. Overall:
Pass/Fail:

Nice article and a good read Jimfbleak (talk) 09:56, 30 April 2008 (UTC)

## Venus' surface level

From this image I thoguht Venus' surface level is below Earth's ocean level at 50 meters below. Venus has like 3 levels of cloud layers, and the haze lies between each cloud layers. Do someone want to clarify this image a little bit.--Freewayguy What's up? 20:15, 29 August 2008 (UTC)

## Composition

I am not an astronomer or physicist, so I may sound idiotic, but shouldn't it be specified whether the elemental composition given in the table is molar or by mass? After all, if in one kilogramme of Venerian atmosphere there is 965 g of carbon dioxide, this is not the same as saying that in one mol of Venerian atmosphere molecules, 96.5% will be carbon dioxide molecules.

## Possibility of life

Particularly, the section referencing carbonyl sulfide... if you reference http://en.wikipedia.org/wiki/Carbonyl_sulfide, it appears the this molecule is created from geothermal vents and volcanoes, and readily forms in the presence of CO and S, not a likely candidate to say that it's an "unambiguous indicator of life"

Thoughts? —Preceding unsigned comment added by 66.104.60.6 (talk) 15:49, 17 August 2009 (UTC)

## Display Temperature in Fahrenheit and Celsius

Three nations have not officially adopted the International System of Units as their primary or sole system of measurement: Burma, Liberia, and the United States.

Today I unsuccessfully attempted to edit this page so that the surface temperature would be in both Fahrenheit and Celsius, rather than just Celsius and Kelvin. Temperatures are supposed to provide a reference point. All articles on Wikipedia are supposed to be written for a general readership, not specifically for scientists. Most Americans aren't familiar with Celsius, and Kelvin is something restricted to scientific use. My suggestion was to list in F and C and then put K over in the information panel, because Wikipedia isn't a scientific journal. Someone in the page edit history argued that it isn't necessary to add Fahrenheit for a temperature greater than boiling water. That doesn't make any sense. 250 degrees K is cold. But most Americans upon seeing that number would probably think it meant "hot." Sadly, most Americans also couldn't tell you where water boils and freezes on the Celsius scale, and the scales also differ in sensitivity. For example, there's only 100 degrees between the boiling point and freezing point of water on the Celsius scale, but there's a 180 degree span on the Fahrenheit scale. For millions of ordinary people in the U.S., then, these numbers are rather meaningless unless they find a way to convert them to the scale they're used to.

Encyclopedias are for general reference, even the scientific articles. And the standard for a general reference in the U.S. is to list in both Fahrenheit and Celsius. For example, see what Encyclopedia Britannica does here. Also see how NASA displays it for a general audience here. Danrz (talk) 18:37, 4 December 2009 (UTC)

Please, read WP:MOSNUM: In scientific articles, use the units employed in the current scientific literature on that topic. It means using Kelvins. Ruslik_Zero 19:37, 4 December 2009 (UTC)

I don't agree with what you think the policy is as it applies here. I know what the convention is and I just showed you what NASA and Encyclopedia Britannica do in the above links for a general readership. And I never said Kelvin shouldn't be on the page. I wanted all three, with Kelvin in the side panel. That's how it is on the Mars page, and Mercury. And scientists will even talk about it in Fahrenheit when speaking to general U.S. readers so that the readers know what s/he is talking about -- e.g. see here and U.S. science magazines that aren't targeted to scientists also list the temperature in Fahrenheit -- see here. Danrz (talk) 20:39, 4 December 2009 (UTC)

Kelvin is the International System of Units standard. I live in Sacramento, CA and accept the fact that the USA is eccentric. One country can not decide what temperature scale is important any more than one country can decide what is a planet. NASA is an agency of the United States government. -- Kheider (talk) 19:42, 4 December 2009 (UTC)

So your most recent argument(after making others in the edit history) is that the USA is eccentric, and that it doesn't merit putting the degrees Fahrenheit in parentheses. And in your most recent edit you hyperlinked the "K", sending all the readers who have no idea what the number really means over to the wikipedia Kelvin page where there's a formula that they can use to convert it to Fahrenheit -- instead of just putting the Fahrenheit in the article itself. I don't consider that helpful. Danrz (talk) 20:39, 4 December 2009 (UTC)

Since Mercury (planet) is listed as 90 to 700 K (−183 °C to 427 °C, −297 °F to 801 °F), I suppose we could consider adding F to the parentheses. Your original edit removed Kelvin and inserted the less common Fahrenheit. I just want to make sure the sentence (and article) do not get bogged down in conversions.
Ironically, in the mid 1980's I remember my teachers telling me that the US would be converting over to the metric system soon. Too bad that never happened. But yes, the US is kind of the oddball when it comes to not using the metric system. -- Kheider (talk) 00:09, 5 December 2009 (UTC)

Didn't you all know the netric system is a commie plot? — Preceding unsigned comment added by 162.192.181.76 (talk) 04:45, 18 October 2013 (UTC)

## Possibility of such a thick atmosphere

Can someone explain how the hell Venus is supposed to have an atmosphere 100 times heavier than that of the Earth, while Venusian surface gravity is 90% of the Earth's? Either the force of gravity on Venus is much, much stronger or it composed of molecules with a mass, which is not indicative of a gas, but rather of a solid. I will do the exact math later. 62.33.188.17 (talk) 00:22, 25 December 2009 (UTC)

• What makes you think every planet (particularly Earth) has an atmosphere as thick as it can possibly have, gravitationally?? The mystery is not why Venus has an atmosphere so thick, but why the Earth has one so comparitively thin. Obviously, a lot of our carbon dioxide has been absorbed into carbonate rock. We had the water to do this, and Venus didn't. SBHarris 00:42, 25 December 2009 (UTC)
• Well, because two things are responsible for the thickness of an atmosphere - gravity and composition thereof. Venus just can't hold its atmosphere; of if it can, then what force do you think packed the atmosphere so tightly so it became very dense?

Thus, the atmospheric pressure at the surface level of Venus should be no more or less than that of Earth's.62.33.188.17 (talk) 15:33, 25 December 2009 (UTC)

This discussion is pointless. The space probes that landed on Venus showed the atmospheric thickness to be what is stated in this article. The proof is there in the data. HumphreyW (talk) 15:39, 25 December 2009 (UTC)
It's doubly pointless, because the IP user has some fixed idea of what two conditions "are responsible" for the thickness or mass of an atmosphere, and he's just wrong, end of discussion. Listen, bub, you're not god. There's nothing in the laws of physics to say Earth couldn't have an atmosphere as massive as that of Venus. It just doesn't HAPPEN to have one that thick, okay? There is NO good reason why every planet has to have an atmosphere as thick as its gravity can hold onto. Outer planets keep the hydrogen and helium in the solar system cloud at that range, but this is cooked off at about the range of the asteroid belt. The atmospheres of inner planets are made after the planet has formed from smaller planetesmals in vacuum (no hydrogen or helium), and it comes from either inside the planet, or from outside (comets). Neither mechanism is guaranteed. SBHarris 25 December 2009 (UTC)

To answer the original question, Venus has a lot of outgassing due to volcanism. The resulting high temperature and atmospheric pressure prevents CO2 from being fixed into carbonate rocks the way it is on Earth. Of course, that still leaves us with a mystery as to the original cause: Why did Venus have such a freakishly large amount of volcanism, at least in the recent past? This appears to relate to the lack of plate tectonics, which leaves volcanoes the only mechanism to relieve heat or pressure in the interior. Kauffner (talk) 13:22, 7 January 2011 (UTC)

• It is a seemingly intriguing question if you don't consider other aspects of planetary dynamics. Gravity is a weak force. However, it is very important to remember that it is precisely what holds planets and moons and asteroids and comets together. The amount of matter within an atmosphere on a terrestrial planetary mass is negligable compared to the rest of the rock material that is being held in place. This is not to say however that a larger atmosphere necessitates higher gravitational forces. Titan for instance, has an atmosphere that is 1.5 times that of Earth's and it is similar in size to our own moon. The reason Venus has such a thick atmosphere now is due to a greenhouse effect, likely from volcanism spewing out CO2. This has resulted in the surface heating to a point where no liquids are able to exist on the surface for long before transitioning to a gas. The heat from the surface has forced a large amount of matter into the atmosphere, far off the surface where it eventually condenses, which is why the surface is not visible from space. Given time and enough greenhouse effect, Earth could look much the same and would actually have an even heavier atmosphere due to the amount of water vapor that has otherwise escaped Venus due to it's lack of a magnetosphere.--Xession (talk) 14:57, 7 January 2011 (UTC)
The only nit I would pick here is that I would not describe the heating mechanism on Venus as a "greenhouse effect" insofar as virtually no sunlight reaches the surface. The diurnal temperature variation is nil. Also, the behavior of CO2 is qualitatively different under such extreme pressure. Another century or two of coal burning is not going to increase terrestrial air pressure to 92 bars. Carl Sagan's "runaway greenhouse effect" is much discussed, but a runaway greenhouse requires water vapor and we now know that Venus has virtually no water. Kauffner (talk) 15:35, 7 January 2011 (UTC)
• Sunlight most certainly reaches the surface. Look at the many Venera lander images. Those were captured in daylight with a relatively quick exposure. I think you may be misinformed about the greenhouse effect and CO2. I saw your post on the Mars atmosphere talk and I think I would need to see some citation for those formulas and information. For one, the reason CO2 is able to capture heat so well is because of it's structure. That's why it is commonly known as a greenhouse gas. Secondly, for Mars, the effect is quite substantial. With no atmosphere, the surface would be extremely cold, much colder than it is. The suface has been known to even reach above freezing ( 0C ), something not possible without the CO2 in the atmosphere. Lastly, I never made claim that the Earth would reach that point from burning coal. I said similar cicumstances, which would equate to heavy vulcanism with lots of CO2. Some recent theories on the difference between Venusian and Terran history even claim that the lapping away of the water from the lack of a magnetosphere on Venus, is a large part of the planets initial overtaking of the greenhouse effect. I'd uge you to do some further research regardless, because you seem to be arguing with dated information.--Xession (talk) 16:05, 7 January 2011 (UTC)
What makes you think Venera took a "relatively quick exposure"? The camera scanned one line of pixels at a time. It took 30 minutes to do a panorama.[1] Yes, I know CO2 is a greenhouse gas. So are water vapor and methane. Atmospheric heating on Earth and Mars is predominantly by convection rather than by the greenhouse effect. The calculations reflect the change in temperature that would occur if a non-greenhouse gas was substituted for CO2, not what would happen if there was a vaccuum on the surface of Mars. Kauffner (talk) 18:50, 7 January 2011 (UTC)
As I know, convection can only transport heat from the hotter bottom part of a fluid to the cooler top. In other words it can only cool something. So, I do not understand what you mean by "Atmospheric heating on Earth and Mars is predominantly by convection". I addition, Venus have never had "such a freakishly large amount of volcanism", although the volcanic rates on Venus have varied significantly: from 3–7 km3/y 500 million years ago to about 0.1-0.01 km3/y now. (See this) For comparison, current volcanism rate on the Earth is 3–4 km3/y. I also want to note that ~10% of sunlight actually reaches the surface of Venus, although it is not important for the greenhouse to function. Ruslik_Zero 20:22, 7 January 2011 (UTC)
The 30 minutes you are quoting, was a limit on bandwidth on Venera 10. Transmitting data through the thick clouds was difficult and had to be done slow to ensure all the data was returned. Later, for Venera 13 and 14, they were able to achieve a better bandwidth for the data and cut that down to 13 minutes. The camera operated by scanning one line, and then sending it, scanning another, then sending it, which is a bit inefficient but cheap and mostly reliable. It was based off an older scanning camera that orbited the moon, which was able to send back 10 frames a second. Secondly, convection is a major part of greenhouse warming. If Earth didn't have any way to hold in heat with the greenhouse effect, every night when the Earth rotated away from the Sun, it would freeze the surface in the lower 100K. The greenhouse effect is what ensures that the heat received from the Sun, is circulated by convection. Water vapor does make a fantastic greenhouse gas and without it, we wouldn't be here.
For Venus, there are two popular theories for the runaway greenhouse effect that you wish to disprove. The first occurs when radiation from the Sun decomposes the water resources as the circulate up into the atmosphere of an early Venus. This leaves little to absorb the Sun's radiation and most of it bounces off the surface, back into the air. Meanwhile, heavy volcanic activity pumps CO2 into the air, which begins trapping the radiation from the Sun. Eventually the CO2 becomes thick enough to trap most of the radiation it receives the temperature to spiral out of control into a runaway greenhouse effect. Similarly, the second postulates that if heavy volcanic activity pumps enough CO2 into the air for the greenhouse effect, the water resources will begin to vaporize, adding to the greenhouse effect which then spirals out of control; the water vapor eventually being decomposed in the upper atmosphere from the Sun's radiation in years since. Similar theories exist that also combine these two and are probably the most likely from what I understand.
There is little else that could cause the temperature extremes on Venus other than some sort of runaway greenhouse effect caused be CO2. However, I'm interested to hear any that you choose to follow instead (no one knows afterall).--Xession (talk) 20:33, 7 January 2011 (UTC)

The figure of 33 C for the terrestrial greenhouse effect is given all over, by almost everyone who discusses this issue. ("Without this effect, the earth would be about 33 C colder than at present."[2]. See also the greenhouse effect article, which cites the IPCC on this.) As for the rest of the sun's heating effect, sunlight is absorbed by the surface and warms it. This heat is transfered to the gas in contact with the surface, both greenhouse and non-greenhouse. Then the atmosphere is warmed by convection. This allows heat to be retained through the night, etc. Why Venus is so hot is one of the outstanding mysteries of science, so I obviously can't give you a fully satisfactory answer. Significant heat must come from the interior, from volcanism and tectonics. On Earth, the Cretaceous was outstanding for its volcanism, with a superplume in the South Pacific and massive sea-floor spreading, and was also far warmer than today. At Venusian pressures, CO2 has quite different properties than it does on Earth. Less than 30 cm will absorb IR entirely, so there is an insulating effect. Kauffner (talk) 04:03, 8 January 2011 (UTC)

According to this, the surface of Venus was "completely covered...in kilometres of volcanic lava" within the last 2.5 million years. The surface is only 500 million years old, so we can think of the planet as being in an early stage of development compared to Earth or Mars. The runaway greenhouse idea originates from the Velikovsky vs Sagan debate in the 1960s. When Mariner found that the temperature of Venus matched Velikovsky's prediction, mainstream science rallied around the runaway greenhouse theory. If the scientists had admitted they didn't know why Venus was so hot, it would have allowed Velikovsky to score a point. Kauffner (talk) 07:39, 8 January 2011 (UTC)
I would be a tad careful with throwing points towards Velikovsky. He had some amazing ideas that are fascinating, but almost entirely unfounded. His perception of Venus being a hot planet, was due to the planet being of a young age (much younger than all the other planets), rather than a belief that a runaway greenhouse effect was occurring. This and most of his other astronomical ideas are from his book, Worlds In Collision. He has a decent historic following with a wiki here discussing his book and some of Carl Sagan's criticisms of it as well. On the other point about the young Venusian surface, it is likely that the process has continued that way for a long while; volcanic activity lay dormant for several millions of years, followed by an upheaval and a complete resurfacing event. One theory to this possibility suggests that the outpouring of lava eventually heats the entire crust to a point where it almost matches the temperature of the mantle, leading to a quick release of the ground heat (through thermal equilibrium) and a rapid cooling period until the surface/crust stabilizes until the next event. This theory has also been suggested as a possible cause to the runaway greenhouse effect but as I recall, its still somewhat new and being debated heavily. --Xession (talk) 08:53, 8 January 2011 (UTC)
The web article that you cite does not say that "the surface of Venus was completely covered...in kilometres of volcanic lava within the last 2.5 million years". I can also conclude that you have not read their paper in Science. That the surface of Venus is on average 500 million years old means nothing, as the surface of Earth has a similar age on average —the oceanic crust is actually much younger. I also see nothing mysterious about the high surface temperature. This was explained long ago—all is need is a very simple physics. If you could understand the relationship between the adiabatic lapse rate and convections, you could understand the high temperature. Ruslik_Zero 17:59, 8 January 2011 (UTC)
I hate to be a boon, but your understanding of geology is seriously flawed. For one, on Earth there is quite visible geologic activities ongoing every day. The surface of Earth ranges greatly in age from 1200 million years old to recent years with top soils and the Mid-Atlantic Ridge. The variance in age shows an active geologic process that is far from common elsewhere in the solar system. Most bodies, such as the moon have surfaces that are many billions of years old. However, in the case of Venus, for the entire surface to be around 300 million to 500 million years old, with visible signs that 2.5 million years ago volcanic activity occurred, some active process must exist but is not currently visible. Secondly, relying on information such as this, someone who has come to similar conclusions to yours, is also very flawed as it completely fails to consider that the Venusian atmosphere has very likely, not always been 92MPa. For instance, the relative closeness to Earth suggests there should be a relatively large amount of water on Venus as a result from forming in a similar location in the planetary disk; however there is evidence of little water being left, even in the atmosphere. Such a large amount of water, as on Earth, actually helps to cool the crust by absorbing the heat that would otherwise go into the atmosphere. For Venus, something must have caused the water to vaporize at some point in the past. Assuming that the crust warmed to a point where it was able to do this, is improbable. So simplifying the problem to the lapse rate will not provide a factual outcome. The dynamic process that has resulted in the current Venusian climate was certainly complex and included multiple variables.--Xession (talk) 19:53, 8 January 2011 (UTC)
My understanding of geology is quite good, actually. I shall comment on all your assertion:
1. Venus also has visible geological activity now, but its rate is likely much lower than that on the Earth now (see here.)
2. The surface of Earth actually ranges from 4.0 billion years to zero in age. However, the average age of it is not much different than that of Venus—500 million years, because the oceanic crust, which occupies 2/3d of the surface is much younger, not more than 200 million years.
3. The ages of the surface of Venus are highly uncertain, but can range from 1 billion years to zero. So, there is nothing unusual in having the average surface age of 500 million years. (There is a very interesting paper.)
4. The guy you mentioned above did not come to the same conclusions as me. My conclusion is that the surface temperature will always be high if two conditions are met: (i) the atmospheric pressure at the surface is high and (ii) the atmosphere is opaque to the thermal radiation. The latter condition is known as "greenhouse effect".
5. I did not consider how such an atmosphere could appear in the first place. There may be different mechanisms including: (i) Venus may have always been dry and hot or (ii) it may have dried later (runaway greenhouse effect).
6. As to your assertion that "the relative closeness to Earth suggests there should be a relatively large amount of water on Venus" is wrong as no water existed in the protoplanetary nebular at the locations of both Venus and Earth. Therefore both of them should have been dry and hot. The Earth was saved by a later addition of some amount of volatiles.
Ruslik_Zero 20:50, 8 January 2011 (UTC)

Ruslik_Zero: Thanks for the link to Science article abstract. What they meant is certainly clearer there than in the news article. You could dial down the snark, though, since just a little while back you were asking basic physics questions like how convection could heat.

• I never wrote that the average age of the surface is 500 million years. Venus had a global resurfacing event 500 million years ago, so the average age is obviously something less than this.
• Adiabatic lapse rate...warm air rises and then cools as pressure declines....and so what? Are you saying that Venus is hot simply because of the high air pressure and the ideal gas laws? You can certainly have high pressure together with low temperature without violating the gas laws.
• the atmosphere is opaque to the thermal radiation. The latter condition is known as "greenhouse effect". Well, I guess you can define the word any way you like. But I always assumed that the greenhouse effect had something to do with trapping solar radiation.
• A runaway greenhouse effect occurs when a CO2 greenhouse increases evaporation, creating positive feedback. If Venus once had an atmosphere with water vapor and lower air pressure, planetary drying would have reduced the greenhouse effect.

Kauffner (talk) 04:53, 9 January 2011 (UTC)

When someone writes that the age of the surface is 500 million years, it is reasonable to assume that they mean the average age.
You should take into account that the convection is only possible if the lapse rate is adiabatic (or superadiabatic).
"trapping of Solar radiation" is an often used word construct, but is actually a misnomer, because the atmosphere of Venus is transparent to the solar (optical) radiation. Greenhouse affect is the trapping of the (long-wavelength) thermal radiation by the atmosphere, which happens on Venus. So, what you have always assumed is wrong.
The Venus is hot because its atmosphere is opaque to the infrared thermal radiation and because the surface pressure is high. The visible light that penetrates to the surface, is absorbed by it and heats it up. The surface re-emits it in the infrared. The infrared radiation is trapped by the atmosphere. So, the heat can not escape and the surface temperature grows. The growth stops when the adiabat is reached. At this moment convection begins to remove all additional heat; the temperature stabilizes. The final temperature on the surface is: $T_s\approx T_{eff}(p_s/p_0)^{(\gamma-1)/\gamma}$, where Ts, ps are the surface temperature and pressure (93 bar), respectively. Teff is the effective temperature ~ 227 K (lower than that of Earth due to the high reflectivity of the clouds). Peff is the pressure (about 0.2 bar at the tropopause) corresponding to the effective temperature. γ (adiabatic index) is about 1.25 for the Venusian conditions. So, the temperature is going to be very high. Ruslik_Zero 13:59, 9 January 2011 (UTC)

The lapse rate is an empirically derived description of the temperature pattern, not an explanation for it. Yes, I know what the greenhouse effect is, but it is not what is happening on Venus. Visible light does not reach the surface, or at least plays no role in heating it up. Here is the NASA factsheet. Notice where it says, "Diurnal temperature range: ~0" As in, maximum 464 C, minimum 464 C, average 464 C ....I hope I'm finally getting through here. Kauffner (talk) 14:59, 9 January 2011 (UTC)

### Outcome of this discussion for the article

I think it is a relevant aspect for the article why the atmosphere of Venus is so much denser than the one on earth. In the German Wikipedia this question came up, too. Therefore I think it's a good idea to include this aspect in the article. I don't have any sources for these things, neither book nor web. Can anyone help here ? Thx. --Hg6996 (talk) 09:56, 17 August 2012 (UTC)

## Comparison of Ancient Venus' atmosphere to that of Earth's

In the lead section: "It is currently thought that the atmosphere of Venus up to around 4 billion years ago was more like that of the Earth with liquid water on the surface."

1. There is no citation.

2. The sentence does not make it clear whether or not Venus' atmosphere 4 billion years ago was like Earth's current atmosphere, which has dramatically changed since the dawn of life (see http://en.wikipedia.org/wiki/Atmosphere_of_Earth#Evolution_of_Earth.27s_atmosphere heading "Evolution of Earth's Atmosphere"), or Earth's atmosphere of 4 billion years ago. For me, this is an interesting discussion because Earth's atmosphere has been fundamentally affected by the processes of life, and if Venus once had an atmosphere like Earth's today, than it is logical to question whether or not life had a role in it's origins as well. However, because there is no citation, it is difficult to judge the source of this conjecture.

Perhaps this sentence should be cited or omitted?

fraktol 17:07, 15 May 2010 (UTC)

==

I too would question the above sentence. While there are two citations given (I assume they weren't there originally), they do not really support the statement. The first states "Venus MAY [my emphasis] originally have had oceans IF [my emphasis] its initial water endowment was close to that of Earth". The second states "Perhaps ... Earth had something special happen in its early history that allowed a lot of calcium oxide to come in contact with a lot of carbon dioxide and steadily leech it from the atmosphere. Perhaps the early oceans of Earth allowed this to happen and Venus had NO [my emphasis] comparable early oceans", which if anything, contradicts the statement.

I think I'll change that statement slightly ... Joe. —Preceding unsigned comment added by 202.168.106.124 (talk) 13:31, 6 November 2010 (UTC)

## Spelling

The original version [3] used vapor and metre. The version around GAN [4] mixed US and UK spelling, so as the current version. What spelling should we use? Materialscientist (talk) 23:42, 10 January 2012 (UTC)

"vapor and metre" – this is already a mixture of Brit/US English. Ruslik_Zero 11:18, 11 January 2012 (UTC)
Right, and in such cases the spelling is often decided by some major article version, or simply by a vote, thus please do - a GA should not remain in such state. Materialscientist (talk) 11:29, 11 January 2012 (UTC)
Arbitrarily chose UK and unified spelling in the article - a GA may not stay like that. Materialscientist (talk) 10:50, 29 January 2012 (UTC)

## Winds

Since on the surface of Venus, carbon dioxide is a supercritical fluid and not gas, does it mean there are still winds on the surface or are there flows instead? --Artman40 (talk) 17:54, 21 May 2013 (UTC)