Explain why the atmospheres of Venus and Earth are so different.?

Question

Venus and Earth are about the same size and mass, yet carbon dioxide is a major constituent of the atmosphere of Venus although oxygen is much more abundant in the Earth’s atmosphere.

Answer 1

The proximity to the sun, the composition of the planet when it was formed, the presence of gases in the early atmosphere, etc.

All of these things determine what gases will evaporate into the atmosphere. The biggest component would probably be proximity to the sun. Venus had enough initial temperature to cause carbon dioxide and water vapor to stay in gas form but still had enough mass to hold the atmosphere.

Mars is a better example because when the gases heated up on mars, the escape velocity was too low to hold a lot of the molecules (thus allowing them to escape into space), etc.

This is a very complex question that cannot be answered on yahoo. I suggest you talk to a planetary atmospheric physicist (or space scientist) to get a better idea of the more detailed explanation.

Edit: the above person has a good point about vegetation, but the root of that is there were a lot of processes that allowed oxygen to be released into the atmosphere and then allowed aerobic bacteria to survive.

Answer 2

Venus and the Earth started off with basically the same bulk composition, but with one major difference. Venus formed closer to the Sun than Earth did, and when the Sun powered up to it's present brightness, Earth found itself in the zone around it where liquid water was stable, Venus was not. Water began to be driven into the upper atmosphere, where solar UV radiation dissociated it into hydrogen and oxygen. The hydrogen promptly escaped and the oxygen combined with the surface rocks. The steamy atmosphere also kick started a runaway greenhouse effect, and volcanism continued to pump CO2 and SO2 into the atmosphere. This vicious circle continued until Venus's primordial oceans boiled away. On the early Earth, the same amount of CO2 exists but it dissolved into the oceans where it formed carbonate rocks like limestones. On Venus, those carbonate rocks broke down and released their CO2 to the atmosphere. On Earth, the CO2 was also being used by early lifeforms to power photosynthesis, removing yet more CO2 from the atmosphere. On Venus, the CO2 had no place to go other than the atmosphere, and as it's concentration grew the greenhouse effect got even stronger. After the oceans boiled away, all but enough of Venus' water to cover it to a depth of less than an inch baked out of the crust and upper mantle. That small amount of remaining H2O raises Venus' Hellish surface temperature more than 200 degrees above what the thick CO2 atmosphere alone would. So the short version is CO2 dissolved into the oceans of Earth and formed carbonate rocks and fed early life on Earth. On Venus, the CO2 was never sequestered from the atmosphere to the extent it has been on Earth. When the planet fell victim to a runaway greenhouse effect, all of it's CO2 was released into the atmosphere where it remained to this day.

Answer 3

Hi, this is a interesting question. See even though Venus is Earth's twin. Venus is closer to the sun causeing it to have a land made basically of lava. Its atmosphere is under so much pressure that it would crush you. The clouds on Venus are made of sulferic acid. There is no plant life that can let out oxygen. On Earth, our atmosphere has the plants that take in carbon dioxide and let out oxygen.

Answer 4

It is because Venus is closer to the sun. Everything that is different about Venus and earths atmospheres is because of that fact.

During the formation of the solarsystem earth and Venus (and Mars) had virtually identical atmospheres loaded with watervapour and CO2. Earth, being farther from the sun, was able to get cold enough for water to condense on the surface. This started a chainreaction as CO2, in the form of carbonic acid, began reacting with metalhydroxides also dissolved in the oceans to form carbonates. This catalytical reaction sucked huge amounts of CO2 out of the atmosphere lowering the surface pressure. As the pressure dropped and the amount of CO2 dropped temperatures also dropped. And eventually life arose in the early oceans. And when photosynthesis evolved the real scrubbing of the atmosphere began.

As molecular oxygen appeared in the oceans it reacted with iron also dissolved there to form insoluable iron oxides. And like the carbonates they gathered on the oceanbottoms in huge layers. So great was the amount of iron in the oceans that it took almost 2 billion years of constant photosynthesis churning out oxygen for the oceans to run out of iron. Only then did the oceans get saturated with oxygen and letting it leach into the, now greatly depleted, atmosphere.

On Venus, of course, none of these things happened. Instead all that primordial CO2 remains with the oh so important water almost all gone due to interaction with the suns ultraviolet rays.

Oh and to nuscorpii:
Venus has probably never been cold enough for carbonates to form. With a greater concentration of watervapour, being an even greater greenhouse gas than CO2, Venus would have been even hotter than it is today. So I can´t picture water ever having flowed on its surface.

Answer 5

The atmosphere of Venus has a lot of acids and thunders, so it's usual for venus to have thunderstorm and acid rain. And the acid rains on Venus are stronger than the acid rain in Earth. Also, Venus is like a planet that's "green house effect" (it has no ooze zone layer) when the heat goes in, it cant escape. (earth's future, i hope not)
And the atmosphere in Earth ooze zone layer, it allows the heat to goes out the planet. and has soggy air (cloud) too. but the ooze zone layer is already get a hole on it, that how the "global warming" comes from,

Answer 6

Venus also has sulferic acid in it's atmosphere and the gravity is 6 times that of earth, it would squash u like a bug if the acid clouds did not eat u first

Answer 7

Venus has a thicker atmposphere with much more CO2 creating a runaway greenhouse effect, that makes the planet so hot that the rock on the surface is largely molten, whereas earth is much cooler and the rock on the surface is solid and has oceans as well

Answer 8

For starters we have vegitation. Our plants expell Oxygen and therefore our atmosphere contains Oxygen something that you cannot find on Venus. We also have water. Within our oceans there are millions upon millions of plant like organisms that also expell Oxygen into our atmosphere.

Answer 9

because venus does not have liquid water and it cannot support life because it is closer to the sun and being even a slight bit closer can throw a planet completely off track like that. that is how come they have searched over a million planets and not yet found one that has all the aspects of earth and can contain life. venus has different gasses that are omitted and that controls how the planets are different earth has a lot of oxygen and silicon and this is also due to the different type of minerals that exist on either planet because that changes the way a planet works too and the lack of water can do alot to a planet but venus is known as our sister planet because of the similarities you mentioned.

Answer 10

Because of the oceans and plant life on earth.