Mission To Mars

Zubrin's was a mission in search of a reason until last month's hints of life on Mars. Now, at NASA centers from the Jet Propulsion Lab in Pasadena, Calif., to Johnson Space Center in Houston, engineers and scientists are working feverishly to design a veritable flotilla of spacecraft that will map Mars from orbit, set down a rover to explore the terrain and eventually bring back a sample of rock and soil to analyze for signs of past or present life. ""We are committed to the aggressive plan we have put in place for the robotic exploration of Mars,'' President Clinton declared last month. The first few missions (timeline) are in the can, so to speak, and can't be changed to carry instruments better attuned to detecting life past or present. One instrument on Mars Global Surveyor, which is already parked at Cape Canaveral for a Nov. 6 launch, can detect minerals that mark places where water, and hence life, might be ""if they are exposed on the surface,'' says Christopher McKay of Ames. ""I am guessing that they have a 50-50 chance of getting a hit.''

So engineers are frantically trying to stuff future missions--which were designed to concentrate equally on Martian climate, resources and biology--with more instruments able to search for life or its remains. Wes Huntress, NASA's chief scientist, calls it ""a "let's change strategy' approach.'' The first target is the ""sample-return mission.'' It was originally scheduled for 2005, but now the NASA brass is pressuring engineers to get it off by 2003. JPL, headquarters for robotic planetary missions, is designing a sample return, which would snag a rock or pile of dirt likely to harbor microorganisms or fossils and get it back to Earth. But Johnson Space Center, mission control for manned flights, is neverthe- less designing a rival approach. The labs aren't yet e-mailing computer viruses to sabotage the other's work, but the competition is heating up.

JPL's first entry might be called The Right Stuff: it's modeled on the Apollo moon landings. A mother ship would orbit Mars. Then it would jettison a lander--like the moon landers--which would touch down on Mars, collect its sample, then rendezvous with the orbiter for the return home by 2006. Alternatively, in the Brute Force approach, a rocket would land on Mars, disgorge a rover that would pick up some souvenirs and return to the main ship, which would then blast off for Earth. A brainstorming session at JPL earlier this month, attended by NEWSWEEK, showed the drawbacks of both ideas. Because the missions would carry enough fuel not only to get to Mars but also to return, they are superheavyweights. Adding so much as a power supply for a radio beacon threatens to make them so ponderous and expensive that they'd be way beyond NASA's downsized budget. To make weight, the engineers were reluctantly throwing out instruments and other cargo right and left. And because unheated rocket fuel would freeze on Mars, the lander could stay there for only four days in one scenario. That's not much time for the slow- moving rover to find some biologically interesting dirt and get it to the ship. But the worst part is that the weight con- straint lets the mission bring back only 10 ounces of Mars.

The Johnson team has embraced the ""live off the land'' philosophy. ""I want to land on Mars with empty fuel tanks,'' says David Kaplan, Johnson's lead scientist for the sample return, ""and run a self-service gas station there [carried up intact and then rolled out of the lander]. Then we wouldn't have to spend every penny of our technology money to make things lighter and smaller.'' The launch weight of his craft would be 38 percent lighter than the JPL plans. Every kilogram shaved off the spacecraft is $150,000 saved. It could stay on the surface as long as required to get the goods, since all the weight saved by not carrying return-trip fuel leaves room for a solar-powered heater that would keep the fuel warm and ready to burn. Making fuel would also let the JSC mission bring back several pounds, not 10 ounces, of Mars. The NASA brass has to decide five years before launch which design gets the green light.

Where should the sample-return rover look for extinct or extant life? Martians won't be waiting on the tarmac for interplanetary arrivals, so scientists are poring over new research on homegrown life for clues on where to dig. Clue number one: life existed on Earth at least 3.87 billion years ago, as researchers from the Scripps Institution of Oceanography presented at last week's astrobiology meeting. That era, as it happens, is exactly when Earth and Mars were virtual twins: warm, riddled with volcanoes and active thermal vents and, most important, wet. Looking for life means looking for water. On Mars, that means desiccated lake and river beds, and ""outflow channels,'' where torrents carrying 50,000 times more water than the Mississippi River once thundered. Clue two: life on Earth can make a go of it in the most unforgiving places--in cracks in rocks deep under the Columbia River basin, inside solid volcanic rock and in searing-hot thermal vents bubbling up from the ocean floor. Many of these simple organisms draw energy from chemicals such as methane, sulfur and hydrogen. Not to put too fine a point on it, they eat rocks. ""Even in bizarre environments,'' says NASA's Huntress, ""wherever there is liquid and energy, there is life.''

Places that have, or had, water and energy, then, are prime biological prospecting sites (map). They include ancient hydrothermal systems, like the vents and fumaroles and hot springs at Yellowstone National Park, and possibly permafrost in the Martian tundra. ""If life on Mars did originate in hydrothermal vents [as it is thought to have done on Earth],'' says planetary scientist John Kerridge of the University of California, San Diego, ""there's a reasonably high probability that organisms could have been fossilized.'' The silicas and carbonates spewing out of the vents can encase a microorganism like a bug in amber. Places without water or energy--like the places where the Viking landers parked in 1976 and failed to find signs of life--are not biologically promising real estate. NASA doesn't want to be looking for life in all the wrong places a second time. As Huntress says, ""we want to bring back not just any interesting sample, but one with evidence of early life.''