The rovers have landed, but when will humans actually go to Mars?
Thirty years ago Mars seemed to be nothing but a cold and sterile piece of rock. Suddenly, it’s back as the focus of intense scientific exploration. Two armchair-sized NASA probes, Spirit and Opportunity, bounded onto the red planet and are returning startling images of enigmatic terrains, while the European Space Agency’s orbiting Mars Express is offering up a bird’s-eye view of a much-gullied place. Scientist William Hartmann, author of A Traveler’s Guide to Mars, is a NASA veteran of both the Mariner 9 mission in the early 1970s and the more recent U.S. Mars Global Surveyor mission. From his office at the Planetary Science Institute in Tucson, Ariz., he talked to Maclean’s Robert Sheppard about exploring the red planet and what lies beyond.
As you know, the Viking landings in the mid1970s found no sign of life on Mars. What’s changed? Why are we back?
That’s right. The result was, not only did we not see any life in the Viking photos, but the soils were sampled, and they were absolutely sterile. So people said at that time, by the end of 1976, “Well, if there was ever any life anywhere, there would surely be this organic material around, organic molecules, debris ofthat sort.” Since then, we’ve come to realize that there is much more underground ice on Mars, in other words, water, but like up in the Canadian tundra. And the polar cap is actually frozen water sitting up on top of the surface. Also, we now know there are places on Earth where the soil tests sterile, for example, Antarctica. But then you go and look in the rocks, and there’s bacteria happily living down in the cracks and pore spaces.
So what we’re seeing now with Spirit and Opportunity is still primarily a search for life?
I’d say life is the big driving factor in all of this. And the second tier of questions is the history of water on Mars, because that’s what we think is needed to make life. Spirit landed in a crater, where there is clearly a river valley that emptied into it. The second rover, Opportunity, is in a low plain, but it’s the first area where we’re detecting unusual mineral deposits.
Is the search for life on Mars intended to see if life sprang up on Earth and Mars and maybe other planets around the same time-that this was some sort of intergalactic seeding?
If you found there were bacteria on Mars— or better yet Mars, and Europa and Titan [moons ofjupiter and Saturn, respectively], and other planets—and they all had common DNA ancestors, then you might say yes, this is seeding. I don’t think the seeding
idea is a major driver. It’s something that may be discovered, but it’s not as if we’re testing that question per se. Four billion years ago, when life was starting on Earth, that’s the time when the conditions were right on Mars, too. The likely scenario is that life is something that happens on any planet when there’s water and chemicals and the conditions are right.
Something that really intrigues me is that we might find on Mars a kind of missing link in the first cells: not single-celled organisms, but maybe something halfway there that would be missing on Earth, because it would be gobbled up by all the living cells that formed later. Mars might be the only place you can go where you have exposed surfaces of the original planetary crust.
So four billion years ago Earth and Mars were quite similar, but something happened to change all that. Was it a cosmic collision?
For sure the early planets were being hit by large objects, and in fact Don Davis and I here at the Planetary Science Institute were the originators of the theory that the Earth’s moon was formed by a giant impact, which blew off material and formed the moon. So yes, those may have played a role in stripping away Mars’s atmosphere. Was there one big impact? Or was it more like atmospheric gases slowly drifting off into space? I think it’s probably more the second.
But there’s one new aspect we’re only just beginning to understand: Mars doesn’t have a big moon like Earth. So it wobbles more. If you imagine the North Pole of the Earth leaning over 45 degrees toward the sun— you’re up there in Canada, you’re suddenly getting a lot more summer sunlight than you would have under a lower tilt. And what we think we’re seeing is cycles of ice repositioned from one pole to the other, on like a 10-million-year time scale, which is a very young time scale for geologists. This may explain why we’re seeing features like hillside gullies and even some glacier-like features, that look very recent.
There’s been talk of late about a manned space probe to Mars. Does something have to come out of this trip to justify that expense?
People are always looking for that. Unfortunately science doesn’t quite move that way. You do one step at a time, and every 10th step produces some fabulous discovery that you didn’t even expect. So you have to be willing to go in for the long-term. These unmanned missions are progressive: the first two we just landed in safe, flat plains. The third, Pathfinder in 1997, was at the mouth of a river, but it was still out in a plain. Now we’re going for the places where the water
might have ponded, so we’re in a crater and this hematite-rich gully. Each one refines our knowledge, and tells you what experiment to do next.
But for the practical purpose of getting a human there, it’s a six-month journey. You’re going to need food, water, fuel. Do you have to find them first to make the trip viable?
I think that’s what these recent ice discoveries have done for us—the confirmation of ice at the pole. You’d think that’s the last place you’d want to go on Mars, because Mars is already cold. But an advantage of the pole, if you land in the summertime, is 24 hours of sunlight. We now know there would be a water resource there. Add to that the 24 hours a day of free solar energy that’s flowing through space. To put our visionary science fiction hat on here, if we can begin to improve our solar technology as part of the space exploration program, or better yet figure out ways to build a big collector, then we’re harvesting large amounts of solar energy that we can use for various things, even back on Earth. There have been schemes proposed for beaming that energy down to Earth to collecting stations that are part of the world’s power grid.
From what you’ve seen of President George W. Bush’s commitment-he’s offering NASA $1 billion or so extra a year for Mars, while some
say a manned mission would cost close to SI trillion—are we being realistic about costs?
I think it’s more important to get a program underway that lays out the right vision of what we’re trying to do. Once that’s underway, and technicians and scientists, preferably from different countries working together, can be employed to start working on it, then the excitement is there. Bush’s program has some elements of that, and some elements that make less sense. Apparently he’s talking about launching Mars expeditions from the moon. That doesn’t make much sense. You don’t want to have to haul fuel up to the moon, and get it back up into space again. One of the bigger political issues: is this going to be another kind of unilateral American thing? I think our generation has an opportunity to design something that goes well beyond that.
How soon could we land somebody on Mars? What would your timeline be?
We could do it sooner. It’s technically feasible now. It’s more a social and political question: what’s the pacing for spending the money? Technically, the Russians have lived in their Mir space station for long enough to get to Mars. Of course they resupply it. Under Reagan, there was an interesting idea. They proposed that we build something like a big international space station, with solar panels and so forth, but not orbiting around the Earth. It would be in orbit around the sun—so it would cycle between Earth’s orbit and Mars’s orbit. It takes supplies from Earth every time it comes around, but it’s big, and it’s got all the accommodations. Then when you want to fly to Mars, you just send your little spaceship up, you dock with this thing, you ride along to Mars, and in six or nine months you get off at the Mars end. lil
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