Mission To Mars

Or, even better, survivors. If there was once life on Mars, where would it have retreated, 3.5 billion years ago, when the warm, wet world changed, for reasons scientists cannot explain, into a freeze-dried desert and much of the atmosphere escaped into space? Someplace with water. Astrobiologists are eager to get modern-day divining rods to Mars: microwaves and neutron- and gamma-ray spectroscopy can detect aquifers and ground water. They also want instruments that can locate geothermal sources, which could maintain liquid water nearer the frigid Martian surface. They want to excavate ground ice where mineral-eating organisms living below the surface may have been washed up and cryopreserved. Dry lake beds offer the most tantalizing possibility of all. When lakes evaporate, salts come out of solution and form crystals. Any salt-resistant bacteria in the lake could have been trapped inside ""brine inclusions''--little pockets of salt water in the crystals. These ""evaporites,'' which Mars Surveyor has a chance of detecting from orbit, may be where surviving life on Mars holed up. They're not going to be fish, or anything bigger than a few cells at most. But on Earth, viable microorganisms isolated from salt crystals have been tentatively dated at 200 million years old.

Some scientists, not to mention headline writers, think we already have evidence of Martian life, courtesy of the Antarctic meteorite that used to be a chunk of Martian crust. But the chemicals in the rock are ambiguous: lots of reactions produce thee polyaromatic hydrocarbons (PAHs) taken to be evidence of a living thing's decomposition. The ""fossils'' are even more problematic. The human eye is notorious for discerning forms and shapes in random patterns, like the supposed ""face'' on Mars itself. Only finding a fossilized cell membrane might clinch the case. However life got started--still a mystery--it needed a membrane to hold, in one little bag, the genetic coding and proteins that constitute life. Single-celled creatures eventually banded together about 2 billion years ago on Earth. Then some of the cells mutated, becoming different from the others, 550 million years ago. The giant step toward the evolution of multicellular creatures had been taken. But unless life on Mars ran on chemistry completely different from that of terrestrial creatures, it would have had trouble getting past step one. By 2 billion years ago, some of the life-giving gases in Mars's atmosphere had collapsed like a soufflE. Others, notably oxygen and nitrogen, escaped into space.

If the budget hawks in Washington suspect that scientists are using the hints of life on Mars as an excuse for missions beyond a little biological prospecting, they're right. Lofting manned missions to Mars ""at the same rate we currently launch the space shuttle,'' says Bob Zubrin, ""the United States today could populate Mars at a rate comparable to that at which the British colonized North America in the 1600s.'' Getting there, in other words, is easy. Living there--well, Zubrin thinks that's not exactly rocket science, either. The key, again, is using the resources on Mars rather than hauling them over from Earth. The Pilgrims, after all, did not bring their own wood. The new Martians could dispatch roving microwave units to zap the Martian permafrost and extract water. Mixing water with Mars's finely ground, claylike dust, putting it in a mold and drying it would produce pretty good bricks. Mixing the red dust with water would produce mortar. The calcium and sulfur in Martian soil are in the form of gypsum, the stuff of plaster. And in case any of this becomes a reality, he has also worked out the chemical equations for producing ethylene gas (the basis for petrochemicals and plastics) out of Mars's air, and metals and glass out of Mars's soil.

Eventually, in the dreams of the Mars Underground, a base becomes a town. The town becomes a colony. One day the colonists ""terraform'' Mars--make it Earth-like. Zubrin thinks the colony, far from being a budget buster, could become self-supporting. It could export, to Earth, patents and inventions produced by its technologically adept settlers. But is that enough reason for earthlings to take the first tentative steps toward the stars? Throughout the centuries, from the time that the first early humans ventured out of Africa to the great voyages of the Age of Discovery, humankind has found more than ample reasons to venture into unknown worlds. The impulse to explore ""is always out there,'' says historian Robin Winks of Yale University. ""It is part of the human condition.''

The last time such rhetoric soared, President Kennedy was challenging the nation to marshal its know-how, its energy and its spirit to put men on the moon. But 1996 is not 1962. President Clinton's 1997 budget will cut NASA's space-science funding from $2 billion to $1.8 billion; cuts would continue for at least five more years. NASA has been careful not to use the life-on-Mars claim to ask for more money. But the sample-return mission is already budgeted at $500 million; moving it up, or loading more, life-seeking instruments on flights scheduled for 2001 and beyond will clearly cost more. Although both Vice President Al Gore and House Speaker Newt Gingrich told NASA last month that they would try to find more millions to support missions to Mars, an equally likely possibility is that the space agency will have to cannibalize the budgets of other missions, from asteroid flights to research on the Earth's climate, to bankroll Mars. In centuries past, civilizations have sallied forth into the unknown for reasons of ideology, politics, commerce and even romance. Now that engineers have a way to get to Mars and scientists have a goal once we arrive, all that's missing is the will.

DANIEL GLICK AT JPL, ADAM ROGERS, PATRICIA KING AT AMES AND MARY HAGER IN WASHINGTON

© 1996