This is one of those ‘what if’ type questions. It might actually have a definitive answer, but in case it doesn’t I figured I’d put it here.
My question is, what if (for reasons unknown) the original placement of the planets had been altered such that Mars was in (approximately) the position of Venus today, and Venus was in (approximately) the position that Mars occupies today? Assume that the system is balanced properly, the orbits stable.
What would happen? What effect would this have on the two planets? Would Mars be a hell world as Venus is today? Would Venus be habitable? Would it have an atmosphere that could sustain life? Or would it be a cold desert world as Mars is?
As a bonus question…what if we could switch Mars and Venus today? What effect would this have on the two planets? Would Venus cool off (well, of course it would eventually)…would it be able to eventually sustain life in it’s new position? And Mars…heating up, would it lose the rest of it’s water, as the ice melts and evaporates away (or is stripped away by the solar wind)?
Mars would resemble Mercury. It would have lost its atmosphere much more quickly. It doesn’t have the gravity to hold much of an atmosphere, has only a weak magnetic field, and, as you suggest, would be subjected to a greater blast of solar wind.
As for Venus, I think it depends on where the life zone - that area where water is liquid - ends. Right now, the current orbit of Mars appears to be just outside that zone.
Not quite what you’re asking, but there’s a Harry Turtledove novel called A World of Difference. “Mars” is called Minerva and is about the same size as Earth, but colder and has liquid water & breathable air.
As for if they were originally swapped way back in the beginning, Mars would now most likey be a hot dry planet with virtually no atmosphere as opposed to a cold dry (with some frozen water) planet with no atmosphere. The mechanisms that caused mars to loose its atmosphere and water would most likely be MUCH worse that much closer to the sun. Solar wind, no magnetic field, slightly too weak gravitational field.
Now, if you took Mars and moved it to where Venus is today it would probably get pretty darn nice. A good place for condo’s even. The catch is the water and atmosphere wouldnt stay “long”. Long enough for humans though. Low end, millions of years. Upper end a few hundred million.
If we swapped Venus right now, after it finally cooled down (might take awhile), it would probably be pretty darn nice place temperature wise as well, if not quite dry. You might even get to put it even significantly farther out and keep a decent temp. That thick ass atmosphere of CO2 makes one good insulator. A big question would be, how much can you cool it before the sulfuric acid clouds can no longer be maintained. And then, when they collapse, how is that going to change the atmosphere. Would the Sulfuric acid just react with the surface or would the resulting chain of chemical reactions remove a good fraction or too much of the atmosphere for Venus to maintain a temp out there?
If in the begining, if Venus was where mars is now in the, my WAG is that it wouldnt be that much different than it is now.
Keep in mind I am not an evolutionary planetary geologist.
The simple answer is to just build a wormhole on the surface of Venus that leads to the surface of Mars. Venus’s atmosphere whooshes through the wormhole over a couple of centuries until Mars has a thick warm atmosphere. Much easier than swapping the planets themselves.
Moving Venus today wouldn’t help because it’s already lost most of it’s water. All that carbon dioxide in it’s atmosphere is there because there’s no water cycle to lock CO2 up as solid carbonate in rocks. Ironically, Venus has a dense crushing atmosphere because it’s lost so much atmosphere.
And while moving away from the sun helps, getting closer to the asteroid belt hurts. Mars is now thought to have lost a significant amount of it’s atmosphere simply from having it blasted away by gigaton-level collisions. With greater gravity than Mars, Venus might either have lost less atmosphere OR attracted more collisions.
Are you sure about that?Surely it’s not so much lost its water as the water is currently bound in other compounds. For instance, there are huge amounts of Sulphuric Acid which is H2SO4.
I think I remember reading that Earth is fairly unique with respect to it’s protective magnetic field such that moving Venus into a different orbit wouldn’t help it’s habitability.