91av

WOULD you volunteer to live on a Martian colony if you had to take all your supplies of air and water with you? It’s unlikely. The only way a colony will survive is by making such life-giving essentials on site. And it looks like it can be done.

Don Sadoway, a natural resources scientist at MIT in Boston, told NASA’s materials science conference in Huntsville, Alabama, how breathable oxygen can be produced from common iron ores in Martian soil. And chemical engineer Ken Debelak at Vanderbilt University in Tennessee revealed how to extract drinking water from Martian clays and minerals. “It’s the only way you’ll get people to go to a research colony on Mars,” says Sadoway. “They have to know there are resources that let them generate necessities like oxygen and water.”

Because the surface of Mars is strewn with chunks of oxide-rich ores, there’s no need to sink deep mine shafts to reach them. To get at the oxygen, Sadoway has designed a refrigerator-sized electrochemical cell powered by a miniature nuclear reactor. It passes a 450-amp current through the ores, melting and electrolysing them. At the negative electrode, a mixture of metals separates out, while oxygen gas is released at the positive electrode.

People need around 2.75 kilograms of oxygen a day, which his cell will scavenge from 8 kilograms of ore. The only by-product would be impure iron. Sadoway’s cell wouldn’t solve all the colonists’ problems, though. The oxygen would still need to be mixed with nitrogen at the very least to make it more akin to breathable air.

And what about water? Despite NASA’s recent fanfare about finding water ice on Mars, getting at it is another matter. The frozen poles may well contain large amounts of ice, but these inhospitable regions would scarcely be ideal places to set up a research outpost. And even if there is water ice hidden in more agreeable climes, it probably isn’t drinkable as it will more than likely be very salty (91av, 8 June, p 11).

A better plan would be to extract water that is chemically bound up in clays and minerals in the Martian soil, says Debelak. His idea is to use the Martian atmosphere, which is 95 per cent CO₂, to do the job. When CO₂ is heated above 31 °C and compressed to more than 72 times atmospheric pressure, it becomes “supercritical”. In this state, it acts as a very effective solvent, and is often used to decaffeinate coffee.

Debelak found that supercritical CO₂ can remove 8 per cent of the water in hydrated minerals. It’s not much, but it’s simple and effective. Dropping the pressure of the CO₂ to 60 atmospheres allows the water to condense out. “The water’s pretty clean, it just has a bit of CO₂ in it,” he adds. “The things we’re talking about here are for when people are seriously thinking about research outposts on Mars,” says Debelak. “Whether or not Congress has got the stomach for something like this further down the road is difficult to say.”