Space/Science — HabitableZone

Space/Science » in reply to I just hate to waste a terrestrial planet that is so close by...

Who says it's a waste?
Adam — (archived)

Hi Scott

No one picked up my calculation error either - the mass to blow off Venus' atmosphere is 340 km across not 3,400. Basically drop Nereid out of Neptune orbit, break it up into a spread out stream and bomb the planet until all the atmosphere is gone... but you've then wasted an incredible wealth of carbon, one of the standard feedstocks for nanotech in the future.

The sunshade approach is probably the best - shade the planet utterly until the cee-oh-two condenses out. The critical point for cee-oh-two is 31 degrees C at 74 bar. After that the atmosphere will condense as a liquid down to the triple point at 5.18 bar and -56.4 C. Keep chilling and it'll become dry-ice over which you can lay down some (400 million sq. km) insulation blankets or 800 metres of ocean to keep it under pressure. Maybe some pre-dug basins that can be buried will suit better. With a relative density of 1.5 the dry-ice would still occupy ocean basin sized caverns.

Carbon dioxide can form a polymer ('carba') similar to silicon dioxide's silica. So far it has only been made under pressure and not successfully quenched to STP, so there's no telling how stable it would be. Perhaps nanotech self-replicators could wrap it in nanotubes or graphene and keep it under pressure. Carba should be pretty dense (s.g. 2.5) so it'd be easier to bury for safe keeping. Currently the energy needed to form it is a bit unclear so it's really just a 'maybe' idea.

When all the cee-oh-two is buried what's left? Venus has about three bar of nitrogen and some argon, so the atmosphere will still be denser than Earth's. And it'll be dry - dryer than a bone. There's 0.1 metres of water in the atmosphere, mostly mixed with sulphuric acid. Nasty. Importing water will be a BIG job. A kilometre of water cover for the planet - much of which will be soaked up by the regolith to form a water table - would take an ice moon 985 km across. Tethys would do, but is probably too deep in Saturn's gravity well. If we could divert half a billion Oort comets 1 km across? Probably full of too much dust and other ices. Tethys might have to do.

Hmmm. Perhaps there's an easier option. I've posted on the idea of floating cities in Venus' atmosphere a few times here and I'd still contend it's a good idea. If we did that then Venus could be populated almost immediately. Eventually the cities might shade the surface enough to chill the clouds and begin the slow process of atmosphere freeze out. Or they might like it as is.

Adam

A big task.

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