So you see the problem, right? Diatomic oxygen normally reacts with iron in an exothermic reaction. If you want to reverse the process, you've got to put energy into the system. To do it on a planet-wide scale, you need to put a lot of energy in.

Catalytic agents normally help (or perhaps inhibit) a chemical reaction go in the direction of releasing energy, they don't make chemical reactions go in the opposite direction from normal.

That isn't to say it isn't possible. After all, plants do something similar with CO2 here on Earth. You might want to consider that Mar's already has an atmosphere predominated by CO2. It is also a very thin atmosphere, compared to that of Earth, under 1%. And you need to consider that in order to get the same "sea level" pressure, Mars would need a far larger atmosphere because it has a lower gravity.

So the simple answer is that it is probably possible, but utterly pointless. Without introducing vast quantities of gases from extramartian sources, you could never get even close to an Earth-like atmosphere (which I'm assuming is your goal). You would also need to supply the energy from somewhere, which would limit the utility of using self-replicating nano-bots. If they were solar powered, they could probably make atmosphere at about the rate the solar wind would blow it away

I would have a hard time believing nano-bots could alter the entire atmosphere of Mars for reasons that have already been stated.

However, I would very easily believe in nano-bots that cleaned up the atmosphere inside an enclosed structure in preparation for colonization by plants, animals, humans, and purple people eaters.

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Is it possible to fire a missile at mars filled with self-replicating nano-bots whose primary function is to 'metabolise' the iron oxide in the geosphere in order to release oxygen into the air? Sort of catalytic agents.

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The short answer is yes, it is possible. We could almost do it with current technology, though the self-replicating part still needs work. We might be able to do it with microorganisms sooner than nanobots.

The long answer is no, this would not give Mars a breathable atmosphere. I don't believe there is any way it ever could. To terraform Mars you would need to bring a lot of energy (and/or mass) to Mars. As it stands your nano-bot plan leaves out this vital step.

[This message has been edited by J (edited December 14, 2004).]

And even if you liberated the oxygen from all the CO2 and iron oxide on the planet, it wouldn't give you a breathable atmosphere.

I am trying to find ways that 'terraforming' can be accelerated.

Alternatively, if we are talking a sci-fi story set, lets say 1,000,000 years in the future, is it akin to writing fantasy anyway?

Every living thing (with one or two deep-sea exceptions) and every machine on earth is ultimately powered by the sun. Even oil-consuming machines, as petroleum is a (very old) plant byproduct.

Survivor's insistence that your machines need energy is true, but his insistence that the sun doesn't provide enough is incorrect.

According to this site:

http://www.atmos.washington.edu/2002Q4/211/notes_greenhouse.html

the solar energy reaching Mars is 593 W/m^2. Some of this will be absorbed by the atmosphere, and no completely efficient energy conversion process exists, so I'll assume that as an upper limit we can use 500 W/m^2 of this, as it's a nice round number.

Obviously, we can only capture this energy during daylight hours, so overall we get 250 W/m^2.

I'm finding it hard to get a precise figure for the minimum amount of energy required to reduce iron oxide. I have this from here: http://www.saskschools.ca/curr_content/chem30/modules/module3/activities.html

"a) 2Fe(s) + 1½O2(g) Fe2O3(s)
H= -824 kJ/mol Fe2O3"

This suggests to me that to reverse the process, we're going to require at least 550 kJ per mole of oxygen released (although my chemistry is extremely rusty ).

So, over one earth year, we're going to have 250 W * 365 * 24 * 60 * 60 = 8 GJ/m^2 of energy available, allowing us to release approximately 14 kmoles of O2 per square metre of surface.

Earth's atmosphere apparently has 2.77 x 10^-4 moles/litre of O2. ( http://www.physics.umanitoba.ca/~davison/henry.html )

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Once the bacteria have oxygenated the atmosphere to a certain point, they'll start dying--literally poisoned in their own excrement. Without the energy produced by the symbiotic bacteria, the nanobots stop working.

As earths atmosphere consist of only 20% oxygen anyway will an approximate 13% be much of a problem? Can we boost the atmosphere past the 20% of Earth barrier and have a higher oxygen ratio?

Or am I being silly? I am an illustrator not a scientist.

Jules' solar energy conversion assumptions are absurdly optimistic for any near future science (meaning in the next thousand years), but probably easy for a technology advanced a million years beyond our own. Still, at that level creating a new planet out of what we would imagine to be essentially nothing would probably be pretty easy.

So if you were to bombard Mars with enough hydrogen sulfide, you could turn all of the iron oxide into iron sulfide (which is black and would turn Mars into the Black Planet) and water and oxygen.

Someone else already commented that colliding comets into the planet would be the most effective way to introduce water and free oxygen into the atmosphere. Additionally the clouding that would take place as a result would effectively thicken the atmosphere and heat the planet.

As to the terraforming grunt work. Using a genetically modified animal would be preferable to a mechanical device. It would also add a nice wrinkle to the story as you are faced with what to do with this lifeform after the process is complete. In any event with current tech standards you are looking at a 1000 year plus process.

Use a genetically engineered "water bear", it can survive the rigors involved with deep space travel and the harsh environments present on Mars, have it process Co2 and excrete oxygen, as mentioned by another writer, further by "mixing" in some plant DNA you could make it chlorophyl based and it would metabolize the sunlight for it's primary energy source.

It's all far fetched, but that is the point of Sci-Fi to address the implausible or impossible.

They look like fascinating little bugs. Very gummy bearish. They usually live in moss and one length I saw was 300 microns. It can go into a dry state where it "resists storage in liquid nitrogen, contact with mineral acids, organic solvents, radioactive radiation and boiling water" (See this site). After putting the poor creature through all these tortures, they add water and poof! It goes back to living its ordinary little life.

Fascinating.