Next stop, Mars

Dec. 8, 2006 | Long a setting for science fiction, Mars appeared to orbit a little closer to our own reality this week with the revelation that the planet might be hospitable to life. New images taken by NASA's Mars Global Surveyor showed changes in craters that researchers say are evidence that flowing water, vital to sustaining life as we know it, existed on Mars' surface as recently as several years ago.

Acclaimed science writer Timothy Ferris says that the discovery is significant -- and could support the prospect of as many as 500 million people one day living on Mars. Ferris, a professor emeritus at the University of California at Berkeley, has written 11 books, including "Coming of Age in the Milky Way," which was awarded the American Institute of Physics Prize and nominated for a Pulitzer. He spoke to Salon by phone from his office in San Francisco.

Why is finding water on Mars significant?

One reason is that Mars is, of all the sun's planets, the most promising second home for humanity. If some day humans are to live permanently on Mars, we need to know what the Martian water table amounts to and how much water is there. For many years, we've believed there is water on Mars because there's ample geological evidence that liquid water existed on the surface of Mars long ago, when Mars had a denser atmosphere and somewhat warmer temperatures. When Mars turned colder, there's no mechanism by which all that water would have disappeared, so it's almost certainly tied up beneath the surface as permafrost, like the water beneath the lands of northern Alaska.

The question is, how much? For decades, it's been thought that there is at least as much water on Mars as there is in the Great Lakes and possibly a good deal more. So, if in fact there are still traces of liquid flowing water on Mars, as these photos suggest, then that would tend to encourage those who believe that there's enough water to support significant human habitation.

Is the water accessible? Could we use it in ways similar to the way we do on Earth?

There are lots of ways you can access permafrost. An extreme example was the announcement of plans for a lunar base that would be located near the pole. That's in part because at the pole you can get a steady supply of solar power. Water is always useful, it's not that difficult to find in the solar system, and it's not a big deal to melt it. If you wanted to live on Mars, you'd have to warm [the inhabited area] up anyway, and that would defrost the water. If you warmed Mars up to the point where the atmosphere was re-engendered and thick enough for oceans, you could also introduce water by diverting an icy comet, and crashing it there, if you wanted to be brutal about it.

The idea of human habitation on Mars, or even extraterrestrial life -- is that crazy?

No, it's not at all crazy! We know that life on Earth requires at least some water, so if there had never been any water on Mars, as may be the case with some bodies in the solar system, then that would decrease the odds of there having been life in the past. We know life on Earth is quite tenacious, so if life existed on Mars in the past it's possible that it's still there in some form. We don't know. The debate about water on Mars, and how much there is and under what conditions, has gone on for decades. There have been long swings of the pendulum back and forth. One of the first space probes to fly past Mars imaged craters that led to unnecessary pessimism in the sense that, since it has craters, Mars must be like the moon. But Mars isn't like the moon -- the more [evidence of] water on Mars, the more likely there is still some liquid water there, and the greater the likelihood of forming life.

Does the water suggest Mars supported other life forms in the past -- or does in the present?

We have no idea. There's just no conclusive evidence. It's like the question about intelligent life in the universe -- we swing back and forth on a pendulum. Currently, we're in one of the pessimistic periods, that there's no life on Mars. It's cold there and the atmosphere is thin. If there was life, there'd be fossils there -- but we just don't know.

Where would you rank this among space discoveries? If on a scale of 1 to 10, landing on the moon is a 10, for example.

If this holds up, I'd give it a 7. To my eye, it is very difficult to think of a viable explanation for this photo besides liquid water, but one wonders, perhaps, if there is some sort of landslide that could replicate the appearance of water. There certainly are odd landslide events that we know of -- the singing sands, and so forth. I know a number of scientists believe it is water, and if true, it's pretty important.

In terms of short-term exploration, this finding doesn't tell us there's water on Mars. It just suggests [a greater possibility] than the pessimists would think. The difficulty with missions to Mars is that it's so far, and it's far away from the sun. It's like going uphill. Any way you can arrange to explore Mars without taking everything with you is useful. One strategy [for further exploration] is to send unmanned missions to establish rocket fuel manufacturing plants -- one of the advantages of water is that you can break it down to make rocket fuel. If it were easy to get at water on Mars, it would vastly decrease the cost of getting home.

The long-term exploration of Mars is subject to the same economic dynamics we've seen in other forms of exploration and settlement. Can people find a way to make money and make a living from it? The prospect of opening up a whole new world would appeal to some people, but economically you have to find a way to make it work. Putting millions of people on Mars is not within the financial plausibility of any combination of space agencies. It has to have its own motors. Look at the history of the Western frontier in America. It was a combination of government incentives and financial speculation and the willingness of people to endure hardship. And in the long run, it did work. I live in California, and I wouldn't be here on the phone if we hadn't explored the West. My guess is that exploration of Mars will work.

Next page: Could colonizing Mars solve problems such as overpopulation and global warming?