(2 of 2)
Still, space officials insist they're wise to their own worst tendencies. "We will go as we can afford to pay," says deputy administrator Shana Dale. "Our charge is to build a program that is sustainable." One indication that NASA takes this seriously is that the equipment being developed for lunar exploration is intended to be adaptable to Mars exploration as well, eliminating the cost of entirely retooling when there's a shift to a more distant, less hospitable destination.
The allure of that second destination got a big boost with last week's discovery of fresh signs of water on Mars. It was made by the Mars Global Surveyor, a spacecraft that has been in Martian orbit since 1997 and finally winked out only last month. Before it did, it produced exhaustive photographic maps of the planet, including shots of tens of thousands of now dry gullies that were almost certainly carved by water. Most of those channels haven't changed over time, but at two of the sites investigators found what appear to be the tracks of flows that occurred within just the past seven years. "It would be about five to 10 swimming pools' worth of water at both sites," said Ken Edgett, a senior scientist for the Surveyor project and a co-author of the new report.
If water was indeed the cause of the tracks, the likeliest source would be aquifers just below the surface. But while this conjures images of warm, amniotic pools cooking up all manner of biology, Michael Malin, chief scientist of the study, urges caution. Acids mixing with water can lower its freezing temperature to nearly -150°F. That's a cold, caustic brew for any living thing that tries to take hold. "Water on Mars does not prove biology," Malin says, "but it may permit it."
Even that makes Mars a far more fertile place than it once seemed, and for many space scientists, that's a good enough reason to go. Lack of funding or political will may yet scuttle the entire audacious moon-Mars enterprise. But for now at least, it appears that a human species that has kept itself confined to the home planet for the past 34 years may once again begin moving stepwise through the solar system.