March 03, 2004,
Scientists have the reputation, fostered in literature and the visual media, of being very serious, unshakeable folk. The image isn't accurate, and never has there been a better refutation of it than could be found in the last few days among the scientists involved in the Jet Propulsion Laboratory's (JPL) Mars rover project. They were extremely excited and they were not saying exactly why.
Word, sort of, spread quickly. The Mars people had found something, but they weren't saying what. It had been found by the Opportunity rover. It was so big that it wouldn't be in the usual Mars-project briefing at JPL. This one would be at NASA headquarters in Washington. In the minds of observers and others in the space program, thought immediately jumped to ALH84001, a meteorite which in 1996 NASA announced with similar fanfare appeared to contain fossil evidence of bacteria; the meteorite's source, NASA said, was Mars. What could Opportunity have found? Something bigger than ALH84001? Rumors grew. Water they found water. No, it had to be bigger than that; it had to be bigger than the fossils, right? Did they find more fossils? Other evidence of life? Life itself?
Debate has raged ever since the announcement that ALH84001 might contain fossils of Martian germs, over whether NASA's conclusion was accurate. Both sides believe they have compelling arguments. At JPL over the last week, the excitement was tempered by a firm discipline nothing would be publicized of which they were not as close to certain as they could be. Hypotheses, no matter how reasonable, would stay within the lab.
Tuesday afternoon, at a news conference at NASA Headquarters, it was announced that the place where the Opportunity rover had landed had once been soaked through and through with water. Maybe underwater. Certainly wet. This was in and of itself very important news; the rovers had, after all, been sent to Mars to look for evidence of water.
But by then word had been kicking around for days that they had found something water-related. People in the space community guessed, and even people at JPL hinted, that something far bigger than that had been discovered. So by Tuesday afternoon, the announcement that was made was met in some respects almost by yawns. The cable all-news stations dumped out of their coverage quickly, to return to stories of the underwear of Kobe Bryant's accuser and the "Super Tuesday" primary elections, on neither of which did they have anything definitive to report.
Water on Mars. Big deal.
Well, it is a big deal. The one thing that all living creatures that we know of have in common is the need for water. One thing that would make travel not to Mars but back from Mars much easier is water. Water is the minimum requirement if a place is to be thought of as hospitable. Ah, but the scientists didn't say they had found water merely a place where once there was water, nice, liquid water, not ice. Nevertheless, the find confirms what had previously been only suspected, and makes Mars a far more interesting place.
The other seven planets in the solar system are incapable of sustaining anything that we recognize as life. The once-tempting Venus we now know is a broiling mess, its clouds made of sulfuric acid. Then come Earth and Mars, followed by Jupiter, gaseous and huge. Everything else is way too close to the sun Mercury or too distant and atmospherically strange Saturn, Uranus, Neptune, Pluto. Mars is the only one that we could visit without much trouble beyond arranging transportation.
Mars, we now know, might at least at one time have been at least capable of sustaining at least some life in at least one area. A modest step, you might think, but a very important one if for no reason other than the questions the asking of which is now less speculative.
What sort of questions? The first one is where the water went, whether it is still on the planet someplace and, if not, what happened to it and why. Linked to this is whether Meridiani Planum, the target of Opportunity, is typical of the planet a probe landing in parts of Yellowstone Park would provide information accurate for only a very small part of Earth; such a probe after the geothermal activity there had ceased would give an erroneous generalization of what Earth might once have been, or what had populated it.
Of course the big question has to do with the existence of living things there. If NASA's analysis of ALH84001 is correct, finding evidence that Mars was once populated by some kind of organism or organisms would not be breathtakingly surprising. It might, though, be breathtakingly useful, as we would come to learn more and more of its nature. What would be truly startling would be the discovery that there is life on Mars today. It is highly unlikely that we will discover complicated creatures wandering the surface of the planet, and we already know that there isn't much chance of lush plant life as we think of it, but we cannot rule out life of some sort more so now that we know Mars has, or had, water. Beyond that, our experience on Earth tells us that we cannot rule anything out. There are living things in truly terrible places. The organisms that live in the super-heated, poisonous water surrounding thermal vents in the inky depths of the Pacific are something no one would have hypothesized before they were discovered. What Mars has beneath its ultraviolet-bombarded surface remains to be seen. But the likelihood that there is something to be seen is greatly enhanced by the discovery that there was and might still be water in the neighborhood.
Questions arise now, too, as to plans for manned flights to Mars, and in their answers will be found the overarching strength of sophisticated robotic space probes, as well as their bedeviling weakness. A man taking samples on Mars would have been able to do in a day what Opportunity has done in weeks, and more. But there's a problem: with the discovery of past or present water there, the likelihood that there is life on Mars is increased to some extent. When we sent Apollo astronauts to the moon, a place we thought certainly bore no life, we nevertheless quarantined them when they returned, until we were as sure as we could reasonably be that they had not brought us an infestation of moon bugs. What would we do with an astronaut who, on Mars, discovers some microbe that we know nothing about, except that it can endure some very harsh conditions? Robotic probes can conduct tests and send back the information. With them, we can know a great deal no, not everything, but a great deal about the place before we ever go there. The idea of a bacterium accidentally coming back from Mars and taking over the Earth a strange twist on H. G. Wells is the stuff of science fiction, the danger minute. But the potential harm is so great that even a tiny risk is to be avoided, and little robots that do a few things at a time, slowly, do much to obviate it.
When word trickled out that one of the Mars rovers had discovered something, we all hoped that it would be a real blockbuster, a picture of an even-more-greenish, James-Carville-looking thing peering into the camera lens, straight off the cover of a Whitley Strieber book. What we got was water-used-to-be-here. But that alone is a very important discovery, an incremental find of substantial significance. That is how discoveries are made in space programs for grownups. Even grownups who become near-giddy when those discoveries are made.
Dennis E. Powell is at work on the forthcoming Orbital Mechanics: The Space Shuttle and the People Who Made It Fly.