Could People Live on Mars?

Could people live on mars?
- Jack (age 9)
Dallas,Texas

Hi Jack!

Your question comes at a wonderful time! As you may already know, the Curiosity rover successfully landed on the Red Planet this past August. It is the largest, most advanced craft of its kind and it's roaming the Martian surface as we speak, gathering all sorts of new data.

When it comes to humans and Mars, there are several questions to consider: Could we visit the Red Planet? Having made it there, could we stay? And -- finally -- if we stayed, could we be self-sustaining?

Practically speaking, humans could spend time on Mars, but the conditions would be pretty rough. The atmospheric pressure at Mars' surface is only 600 Pascals to the Earth's standard pressure of 101,325 Pascals. For comparison, the lowest pressure the human body can withstand is 6300 Pascals -- this is known as the Armstrong limit. Mars' is also dramatically different from our own – 95.32% carbon dioxide, 2.7% nitrogen, 1.6% argon, and .08% carbon monoxide (plus small amounts of various other gases) compared to the Earth's 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.039% carbon dioxide (again, plus small amounts of various other gases). That's way too much carbon dioxide and not nearly enough oxygen for a person to take even a few breaths – plus the carbon monoxide content of the air would be incredibly toxic to us. Finally, the Martian atmosphere is also only about 1% as thick as ours, meaning it does less to shelter the planet's surface from the Sun's light. indicate that "radiation levels on the Martian surface to be comparable to those experienced by astronauts in low-Earth orbit," and these are manageable. Still, we couldn't survive on Mars for even a moment without ventilation systems and radiation-blocking, pressure-controlled suits.

The dry Martian surface is also prone to frequent and severe . These storms can cover huge areas of the planet, blocking out the Sun's light. Were humans to visit the Red Planet, dust storms could easily interfere with radio communications and limit our use of solar powered technology.

Temperature is another issue. The Earth's orbit is almost perfectly circular, but Mars' orbit is somewhat less so. Its rotation is also slightly more tilted than that of our own planet, and together these differences mean more extreme variations in temperature – from -225˚F at the polar ice caps in the winter to 95˚F near the equator in the summer. Even the average Martian temperature is a chilly -67˚F! But, for comparison, the average temperature of central Antarctica is around -57˚F, and we've had people living and working there for more than two hundred years. Of course, Antarctica is close enough for us to make repeat expeditions to bring the basic supplies that sustain life.

That brings me to the second question: Could we stay on Mars permanently? Think about the bare minimum we need to survive – air to breathe, and food and water for fuel, some sort of shelter from the elements...

First off, water: There is no liquid water on the surface of Mars – the low atmospheric pressure would cause it to boil off in the open air even at freezing temperatures! – but there are large ice caps at its north and south poles. Unfortunately, these are not pure water, but rather ice mixtures with a layer of frozen carbon-dioxide (you probably know this as "dry ice") on top. As you might expect, getting usable drinking water from these caps would require huge amounts of energy in order to heat and melt the ice, and it is questionable whether or not we'd be able to meet these energy requirements.

In the same vein, we've already tackled the question of breathing for a short visit – we could likely use the same basic ventilation systems astronauts use now. But what would happen once our oxygen supply ran out? With limited space aboard any potential vessel traveling to Mars, we simply couldn't bring enough air to sustain life for any extended period of time. However, with enough energy, we could potentially extract the oxygen we need from carbon dioxide in the Martian atmosphere.

The issue of limited space for supplies would arise with food as well, and the best long-term solution would probably be to and grow food ourselves. Still, to do so would require quite a bit of time, money, and transportation of materials.

For all of these supplies, you're probably wondering: Why can't we make return trips to bring more of what we need? That's certainly possible, but we need to consider what the cost of even a single expedition would be – tens of billions of dollars, at least. Simply put, we may not be able to afford to put people on Mars permanently.

But, despite all of this, Martian conditions are far more similar to the Earth's than any known planet or moon, and it's decently close to us. We may have manned expeditions to the Red Planet in coming decades, but actually sustaining human life there is probably out of the question. Several private initiatives are planning manned expeditions as we speak, but the ones that aim to establish permanent human colonies (, for example, proposes to do so by 2023) are too vague in their plans to be taken seriously at this time.

In short, keep an eye on the news! There may very well be people setting foot on the Red Planet in our lifetime, but it is unlikely that it will be for anything more than a visit.

Cheers,

Becca

(published on 03/28/2011)