How did Venus and Earth end with such radically different atmospheres and climates?

Answer 1

Starting with what was recently said. Say from out-gassing and volcanoes Venus was similar to Earth, C02 mainly in the atmosphere as well as water, and water vapor. Plus comets would have deposited water on Venus also. The problem is, what is called the Run-Away Greenhouse effect. The proximity to the sun caused the greenhouse effect to take place, in a stronger amplitude than on earth. At one point the surface of Venus became hot enough to boil water. Then the water vapor itself is a greenhouse gas. Water is one of the things on the earth that regulates the levels of CO2 by absorption. Now, there was nothing to stop this run-away greenhouse effect. Now, the radiation that reaches Venus that is not reflected is very efficiently kept on the planet. Surface temp of around 740 degrees K.

Answer 2

Because Venus is closer to the sun. Both planets began with virtually the same atmospheres but Venus has always been hotter. Water has probably never been able to condense on Venus and with enormous quantities of watervapour in the atmosphere Venus was probably even hotter in its youth. Gradually the water fell prey to the suns ultraviolet rays as it was disassembled into hydrogen and oxygen. Most of the oxygen remained as part of sulphurous oxides while the hydrogen escaped into space. As the water was lost Venus cooled into the "frigid" world it is today.
On earth water condensed and began dissolving the CO2 in the atmosphere. As carbonic acid it reacted immediately with hydroxides also dissolved in the oceans to form carbonates. The atmosphere thinned (it was probably about 70 times as dense as it is today) through this process and made it possible for life to evolve. Photosynthesis depleted the atmosphere further as oxygen produced as a byproduct reacted with iron also dissolved in huge quantities in the oceans. The iron oxides, like the carbonates, sank to the bottom. Life quickly began utilizing this oxidization and sped it up but it took several billion years and the advent of carbonate rock forming organisms to to turn the atmosphere into what we have today.

Answer 3

Let me begin by saying, "Very good question!"
Consider an industrial size mixer for say, pizza dough. First we have dry and wet ingredients added to the bowl. As the ingredients are mixed together, heat involved (friction) begins to breakdown liquids and bind them with the solids. After about 20 minutes of intense mixing, we have a semi solid in the form of dough. Now back to the solar system. Mercury is baked, Venus is molten and Earth is stable to carbon based life as we know it, and resides in what is known as the bio-zone. As the Sun grows into a red giant, molten Venus will become solid and baked like Mercury and the Earth will face the fate of Venus and become molten. At this point, the ice on and in the poles of Mars will be melting and create an oxygen/liquid water rich environment. Now recall the "dough mixer" analogy. Gas giants, Jupiter and Saturn are similar to the base of dry and wet ingredients in the mixer bowl. As they turn more and more around a growing star, they are exposed to more heat and the elements inside of these planets begin to bind and form that "semi-solid". Eventually Jupiter and Saturn will pass through the phase that Mars now resides in and will eventually pass through the phase that the Earth, Venus, and finally Mercury are in. Note that as the Sun grows and these changes are happening to Jupiter and Saturn, the ice planets that are Neptune, Uranus, and Pluto will be melting and become the "new gas giants". Eventually as the sun grows large enough, these later three will pass through the same phases as all of the inner plants. In conclusion; The key point is to know that the particular distance that the Earth is from the Sun now, is known as the bio-zone. Both Mercury and Venus were once the same distance from the Sun that the Earth is now. Earth will one day pass through the same phase that Venus now lies in and so on and so on. Thank you for your time.

Answer 4

We don't know for sure, but the best guess is that Venus never developed aquatic life that converted CO2 to O2, as is postulated to have occured on Earth.

Answer 5

Well all I know is that Venus is closer to the sun, so it will be hotter. The earth is close enough to keep life going, and far off enough that...er...life can continue?