I’ve been reading that Venus’ atmospheric pressure is something like 90x Earth’s…but since Venus’ gravity is almost identical to ours and with no magnetic field to keep the solar wind from stripping the atmosphere from the planet, what makes and keeps it so thick? How does it not just evaporate or blow off into space (if being continuously fed by volcanoes) to make it closer to Earth’s density under Earth-like gravity?
**Edit:** Thanks to all of you who took the time to answer here; I think I finally understand what’s at play and how it works. Made my night, and you’re all awesome, hey? 🙂
In: 11
Venus has a much thicker atmosphere than Earth does. The truth is, magnetic fields are vastly overrated in importance when it comes to holding in an atmosphere. Gravity is more important. Venus (and Earth) have enough to hold on to heavier gasses. Hydrogen can be lost, and on Venus probably most of the hydrogen _has_ been lost over the eons. On a hot planet like Venus, water can get way up into the upper atmosphere, get split into hydrogen and oxygen, and then the hydrogen can be lost. Over time this eliminates most of the water on the planet. But carbon dioxide is too heavy to be lost in this way and doesn’t get broken up as easily as water. On Earth, most of the water stays safely stuck in the lower atmosphere.
As for why Venus has so much more CO2 than earth, it’s because on Earth, CO2 is constantly being trapped and buried. Of course, life does this in massive quantities, but so does the geology of our mountains and oceans. We have a Venus’ worth of carbon trapped up in carbonate rocks (limestones and the like).
Without oceans (and life or plate tectonics) Venus has nothing mcuh absorbing CO2. So it eons of CO2 production from volcanoes just build up and up, forming a thick atmosphere much more massive than the one our planet has.
I’ve been reading that Venus’ atmospheric pressure is something like 90x Earth’s…but since Venus’ gravity is almost identical to ours and with no magnetic field to keep the solar wind from stripping the atmosphere from the planet, what makes and keeps it so thick? How does it not just evaporate or blow off into space (if being continuously fed by volcanoes) to make it closer to Earth’s density under Earth-like gravity?
**Edit:** Thanks to all of you who took the time to answer here; I think I finally understand what’s at play and how it works. Made my night, and you’re all awesome, hey? 🙂
In: 11
Venus has a much thicker atmosphere than Earth does. The truth is, magnetic fields are vastly overrated in importance when it comes to holding in an atmosphere. Gravity is more important. Venus (and Earth) have enough to hold on to heavier gasses. Hydrogen can be lost, and on Venus probably most of the hydrogen _has_ been lost over the eons. On a hot planet like Venus, water can get way up into the upper atmosphere, get split into hydrogen and oxygen, and then the hydrogen can be lost. Over time this eliminates most of the water on the planet. But carbon dioxide is too heavy to be lost in this way and doesn’t get broken up as easily as water. On Earth, most of the water stays safely stuck in the lower atmosphere.
As for why Venus has so much more CO2 than earth, it’s because on Earth, CO2 is constantly being trapped and buried. Of course, life does this in massive quantities, but so does the geology of our mountains and oceans. We have a Venus’ worth of carbon trapped up in carbonate rocks (limestones and the like).
Without oceans (and life or plate tectonics) Venus has nothing mcuh absorbing CO2. So it eons of CO2 production from volcanoes just build up and up, forming a thick atmosphere much more massive than the one our planet has.
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