[Moontanman]

[Moderator note: this thread was split off from the thread Terraforming Mars, because the two subjects are literally worlds apart]

[CraigD]

Originally Posted by modest

Why assume Earth would loose its atmosphere? I don't think it would - at least not quickly. Venus has no magnetic field, more solar wind, and less mass. All that, and more atmosphere then it knows what to do with.

Venus’s atmosphere has been stripped of nearly all of its light molecules, so that it’s now about 96.5% (mass 44 AMU) and 3.5% (28 AMU), vs. Earth’s 78% , 21% (32 AMU), and 1% argon (40 AMU). Being about Earth’s mass (82%) and distance from Sol (72%), Venus should have had an initial composition about like Earth. Counterintuitively, stripping its of more light molecules has resulted in Venus’s atmosphere not only having a higher average molecular mass, but a higher total mass (about 93 times) than Earth’s.

Originally Posted by Moontanman

All the light molecules like oxygen and nitrogen are gone.

In absolute terms, this isn’t an accurate statement.

Though small as a percentage, note that Venus’s 3.5% nitrogen times its total atmosphere mass of 93 times Earth’s means it has about 4.5 times as much nitrogen as Earth’s 78%. The oxygen in Venus’s 96.5% atmosphere is over 420 times that of Earth’s 21% !

Originally Posted by modest

This makes me think, could we more easily terraform Venus by stripping away its atmosphere than terraforming mars?

I don’t think you could just strip Venus’s atmosphere away into space, but rather would have to get as much of the carbon out of it as possible (a carbon sequestration project dwarfing any terrestrial one), and dispose of the freed oxygen. The ideal use of the freed oxygen is to bond with hydrogen into that human-friendliest of molecules, .

A big problem is that Venus doesn’t appear to have much hydrogen left. Its surface temperature is so high there’s nearly no liquid . All its is a gas, which appears to be getting unbonded and swept into space – one of the Venus Express probe major instruments, its ASPERA-4, found that Venus is venting about 1.9 H+ ions for every 1 O+ ion, and small traces of He+, suggesting that nearly all of it is coming from lost .

So, as with Mars’s, terraforming Venus’s atmosphere would likely require adding a lot of hydrogen – which, with what there is to work with in the solar system, comes mostly in the form of ice. Unlike Mars, there’d be a lot of left-over oxygen, which would have to be bound into solids on the surface.

[modest]

Originally Posted by CraigD

Venus’s atmosphere has been stripped of nearly all of its light molecules, so that it’s now about 96.5% (mass 44 AMU) and 3.5% (28 AMU), vs. Earth’s 78% , 21% (32 AMU), and 1% argon (40 AMU).

While I could intuitively see how this would be true of Hydrogen, I'm unconvinced of the other elements. Venus has of nitrogen while earth has . Twenty four percent considering Venus is lighter seems comparable to me. Like a lifeless earth, I wouldn't expect Venus to have Oxygen though I don't know why we'd attribute this to the solar wind. Oxygen's molecular weight is 32 g/mol while carbon dioxide's is 44 g/mol. I would be very supprised if that difference in mass makes the difference between getting stripped or not.

Originally Posted by CraigD

Being about Earth’s mass (82%) and distance from Sol (72%), Venus should have had an initial composition about like Earth. Counterintuitively, stripping its of more light molecules has resulted in Venus’s atmosphere not only having a higher average molecular mass, but a higher total mass (about 93 times) than Earth’s.

Can you explain how stripping 75% of the nitrogen would result in such a big carbon dioxide build-up. Are we sure one has something to do with the other?

//edit

Sorry, I had Earth and Venus inverted in my percent calculation up there, I believe the mass of Nitrogen on Venus is 4.2 that of Earth and it is lighter than oxygen. I don't think we can say the oxygen was stripped off or infer that Earth's would be if we lost our magnetic field.

[Moontanman]

Originally Posted by CraigD

Venus’s atmosphere has been stripped of nearly all of its light molecules, so that it’s now about 96.5% (mass 44 AMU) and 3.5% (28 AMU), vs. Earth’s 78% , 21% (32 AMU), and 1% argon (40 AMU). Being about Earth’s mass (82%) and distance from Sol (72%), Venus should have had an initial composition about like Earth. Counterintuitively, stripping its of more light molecules has resulted in Venus’s atmosphere not only having a higher average molecular mass, but a higher total mass (about 93 times) than Earth’s.In absolute terms, this isn’t an accurate statement.

Though small as a percentage, note that Venus’s 3.5% nitrogen times its total atmosphere mass of 93 times Earth’s means it has about 4.5 times as much nitrogen as Earth’s 78%. The oxygen in Venus’s 96.5% atmosphere is over 420 times that of Earth’s 21% !I don’t think you could just strip Venus’s atmosphere away into space, but rather would have to get as much of the carbon out of it as possible (a carbon sequestration project dwarfing any terrestrial one), and dispose of the freed oxygen. The ideal use of the freed oxygen is to bond with hydrogen into that human-friendliest of molecules, .

A big problem is that Venus doesn’t appear to have much hydrogen left. Its surface temperature is so high there’s nearly no liquid . All its is a gas, which appears to be getting unbonded and swept into space – one of the Venus Express probe major instruments, its ASPERA-4, found that Venus is venting about 1.9 H+ ions for every 1 O+ ion, and small traces of He+, suggesting that nearly all of it is coming from lost .

So, as with Mars’s, terraforming Venus’s atmosphere would likely require adding a lot of hydrogen – which, with what there is to work with in the solar system, comes mostly in the form of ice. Unlike Mars, there’d be a lot of left-over oxygen, which would have to be bound into solids on the surface.

Actually in real terms the earth probably has the same or similar amount of both nitrogen and CO2 it's just that water allows these chemicals to sequestered in the rocks of the surface. The first to go would be the water, after the water is gone the carbonate rocks would release all their carbon dioxide and then the temps really start to climb and most all volatile compounds are released into the atmosphere to be swept away by the suns radiation or solar wind. As for left over oxygen that would depend on how much oxygen was bound up in the surface and how much CO2 would be disolved into any ocean that would form after the ice was deposted on the surface. formation of carbonate rocks would take care of the surplus of free oxygen. Of course you would have to sped up the planets revolutions for any changes to have real effects. that might even start up a magnetic field. Be a hot place but it might be livable after all the cO2 was sequestered. I'm betting it would take much longer to terra form Venus than it would Mars!

[CraigD]

Originally Posted by modest

Can you explain how stripping 75% of the nitrogen would result in such a big carbon dioxide build-up. Are we sure one has something to do with the other?

As I understand it, the current composition of Venus’s atmosphere (which is known with pretty high precision, having been directly and remotely measured by several lander and orbiter spacecraft) isn’t due to the loss of fairly massive nitrogen molecules, but to a massive transfer of from carbon and oxygen formerly in surface carbon and oxygen-bearing solids and liquid – what’s commonly described as a “runaway greenhouse effect”, believe to have occurred anywhere from 2 to 4 billion years ago. Prior to that, Venus is believed to have been fairly Earth-like.

This wikipedia section has a brief description and references of the subject.

[Moontanman]

Originally Posted by CraigD

As I understand it, the current composition of Venus’s atmosphere (which is known with pretty high precision, having been directly and remotely measured by several lander and orbiter spacecraft) isn’t due to the loss of fairly massive nitrogen molecules, but to a massive transfer of from carbon and oxygen formerly in surface carbon and oxygen-bearing solids and liquid – what’s commonly described as a “runaway greenhouse effect”, believe to have occurred anywhere from 2 to 4 billion years ago. Prior to that, Venus is believed to have been fairly Earth-like.

This wikipedia section has a brief description and references of the subject.

One fairly new theory stipulates that a massive impact like the one that is believed to have formed earth's Moon stopped the rotation of Venus and started it turning slowly the opposite direction from the Earths rotation. This impact either didn't form a moon or since it was from the opposite direction than the Earths giant impactor any moon that was formed spiraled down into Venus instead of spiraling out as Earths Moon has. This second impact event and or the slow rotation could have been the trigger that started the runaway greenhouse we see today. Of course all this is highly speculative.

[modest]

Why would Venus have it's Oxygen stripped off and not it's Nitrogen? Oxygen is heavier. This theory seems to have more leaky holes than our sister planet out there.

-modest

[Moontanman]

Originally Posted by modest

Why would Venus have it's Oxygen stripped off and not it's Nitrogen? Oxygen is heavier. This theory seems to have more leaky holes than our sister planet out there.

-modest

That is a good question and my only answer is maybe the oxygen didn't get stripped from the atmosphere but it reacted with the surface and other chemicals to form the sulfer dioxide and sufuric acid seen in the atmosphere. I'm not sure but I think it would also form nitric acid as well. But I'm not completly sure about that. One thing is sure oxygen would not be stable in the atmosphere of Venus with out a contuinous source of resupply. On the earth plants do that. I don't think Venus has much in the way of plant life.

[modest]

Originally Posted by Moontanman

That is a good question and my only answer is maybe the oxygen didn't get stripped from the atmosphere but it reacted with the surface and other chemicals to form the sulfer dioxide and sufuric acid seen in the atmosphere. I'm not sure but I think it would also form nitric acid as well. But I'm not completly sure about that. One thing is sure oxygen would not be stable in the atmosphere of Venus with out a contuinous source of resupply. On the earth plants do that. I don't think Venus has much in the way of plant life.

I could see that. I suppose we also say that of nitrogen and nitrogen compounds - but there's nothing sure about that.

However, like I said, I don't find it too strange that there's no atmospheric, elemental oxygen. I just thought there might be more evidence linking the loss of Venus' magnetic field and the run-away greenhouse. Perhaps there is and I just need to find it.

-modest

[Moontanman]

Originally Posted by modest

I could see that. I suppose we also say that of nitrogen and nitrogen compounds - but there's nothing sure about that.

However, like I said, I don't find it too strange that there's no atmospheric, elemental oxygen. I just thought there might be more evidence linking the loss of Venus' magnetic field and the run-away greenhouse. Perhaps there is and I just need to find it.

-modest

Actually the loss of water can be atributed to the lack of a magnetic feild. Loss of water means that all the planets CO2 is in the atmosphere. this accounts for the greenhouse effect, pretty straight forward to me. oh yeah slow rotaion probably accounts for the lack of a magentic feild which could have been caused by a giant impactor that hit in the dead wrong orieintation to it's original rotation.