Making Mars habitable

[JamesF]

I'm having a slow work day today and my mind has been wandering, so here's a somewhat wild and random thought...

For Mars to retain a breathable atmosphere it might be handy if it were larger and had a liquid core. If it were possible to built an army of autonomous robots that "farmed" asteroids from the asteroid belt and punted them into a collision course with Mars, would it be theoretically possible to increase the mass of the planet to the point where the core would melt again?

James

[JulianO]

I don't think it's mass per-se that would help. It would help retain any heat for longer of course. However the collisions would warm it up on the surface. What you want is heavy nickel-iron asteroids, which would then sink to the centre giving up GPE to heat on the way down. Even better would be radioactive heavy elements like uranium, plutonium and thorium which would not only sink and heat, but also give off heat when they got there.

It depends how long you want to keep the atmosphere, but I suspect if you found some way to make it as thick as Earths, it would stick around for a few millions years before being burnt off - which might be enough for your purposes, depending on what they were of course!

[ollypenrice]

It would surely be easier to make the Earth habitable, no? But we seem to be doing the reverse.

Ah well.

Olly

[mattft]

it'll all be about a liquid core. Without that, no magnetic field and the atmosphere will get blasted off by the solar wind. Heavy element astroids sounds like an option but how you sink them to the core is going to be even harder than finding them and getting them to Mars.

I think for the foreseeable future we should plan Mars only being habitable in habitats.

[Naemeth]

The energy it would take to re-heat Mars' inner core to the point it's molten again would probably take a huge number of asteroids to do so, I haven't done the calculations.

Another alternative, is to slowly build an atmosphere by any means, artificially creating a magnetosphere by electricity, and slowly "wasting heat" by sending it to the core.

[JamesF]

It would surely be easier to make the Earth habitable, no? But we seem to be doing the reverse.

Apophis. 'B' Ark. Sorted.

James

[Naemeth]

To make Earth more habitable, it would be a great idea to "import" comets full of H₂O ice, filling our oceans and making drought less common.

[JamesF]

To make Earth more habitable, it would be a great idea to "import" comets full of H₂O ice, filling our oceans and making drought less common.

Noooo! We'd just end up with more rain!

James

[Naemeth]

Noooo! We'd just end up with more rain!

James

True, of course it's not a perfect solution, but perhaps with more trees over the planet, more of the CO₂ in the atmosphere would be breathed in by the trees, and more O₂ would be released in the atmosphere.

One major problem with Mars by the way is the lack of Nitrogen, which could be used as a buffer gas for the atmosphere to be kept at a pressure of 1 Earth Atmosphere. You wouldn't want an atmosphere as thick as Earth's is with almost pure CO₂, that would be toxic and Mars would be horrible to live on.

[JulianO]

it'll all be about a liquid core. Without that, no magnetic field and the atmosphere will get blasted off by the solar wind.

True, but I've read somewhere that the timescales to lose it would be millions of years. If we're terraforming Mars, a million years may be just fine!

I'd like us to have a back up plan, even if we are careful with the Earth, rocky debris in the solar system may not be

[Naemeth]

Atmospheres take a long time to be eroded by the solar wind, how else would Venus still have ~90 Earth Atmospheres of pressure if it stripped it quickly?

[mattft]

Atmospheres take a long time to be eroded by the solar wind, how else would Venus still have ~90 Earth Atmospheres of pressure if it stripped it quickly?

The conjecture is that Venus probably had a more Earth-like atmosphere including significant amounts of water until a greenhouse effect really took hold. The Venetian atmosphere has had most of it's lighter elements and molecules removed due to the solar wind too - H, He, O, H2O. There lighter, and unfortunately essential to human life gases are more likely to be stripped by the solar wind. Not really a model for terraforming. So unless we figure out a way to protect the lighter molecules/elements it's a tough battle - how do you put more into the atmosphere than is being removed? Keep large chunks of the atmosphere under domes or figure out how to get a magnetic field back. I like the idea of covering the Valles Marineris from Kim Stanley Robinson's trilogy of books. Probably the most realisitc and practical way of creating something like a home-from-home. Good read too.

[Naemeth]

Agreed, I'm half way through Green Mars .

[wiseman]

Smaller planets lose heat faster than bigger planets ( surface area), so Mars lost its heat faster than the Earth, and now its core is solid.

You need a magnetic field to keep lighter gases like o2, you can either get that with fast rotation and a liquid iron core like the Earth ( venus rotatses v slowly, so this only gives a small field)., or with something called induced magnetosphere

as, Wikiepedia informs us

Unlike Earth, Venus lacks a magnetic field. Its ionosphere separates the atmosphere from outer space and the solar wind. This ionised layer excludes the solar magnetic field, giving Venus a distinct magnetic environment. This is considered Venus's induced magnetosphere. Lighter gases, including water vapour, are continuously blown away by the solar wind through the induced magnetotail.^[3] It is speculated that the atmosphere of Venus up to around 4 billion years ago was more like that of the Earth with liquid water on the surface. A runaway greenhouse effect may have been caused by the evaporation of the surface water and subsequent rise of the levels of other greenhouse gases.^[7][8]

[wiseman]

Agreed, I'm half way through Green Mars .

I loved these books, but now I realise the protective effects of an atmostphere, how come they didnt all get freied by radiation, when they ran about outside?