Looking for life? Look down deep 

By Alan Boyle

MSNBC Jan. 30 —  If you're serious about the search for extraterrestrial life, it's going to take more than rovers and radio telescopes. You may have to look miles beneath the surfaces of other worlds. Maybe the movie "Armageddon" got it right: The best astronauts for interplanetary expeditions will be deep drillers.

Last Years's big asteroid movie drew a Texas-sized share of scorn for its improbable plot, which turned a ragtag gaggle of oil-rig workers into a team of astronaut-heroes in a matter of days. But for all its scientific sins, Arizona State University geologist Jack Farmer hints that the people in charge of planning missions to Mars could learn a thing or two from Bruce Willis' character.

"They're going to have to get some experience on drilling rigs," Farmer said this week at the annual meeting of the American Association for the Advancement of Science.

For years, Farmer has worked on NASA's strategies for exploring the Red Planet and for seeking traces of ancient extraterrestrial life — an endeavor for which he coined the term "exopaleontology."

The current theme for the quest on Mars has to do with water: Did liquid water flow freely over the planet billions of years ago? Where did it come from, and where did it go? Might the presence of water have facilitated the development of life on ancient Mars? Does the planet still exhibit a pattern of water circulation on some level?

If there is such a pattern — a "hydrologic cycle," to use geological parlance — it would have to be active far beneath the surface, Farmer said. Indeed, a growing number of scientists say the water that once filled Martian valleys most likely came from underground hydrothermal systems, rather than from an Earthlike system of rivers, oceans and rain clouds.

"The valleys were carved by flowing water, but the water sprang forth from beneath the surface and eroded the channels by a process of ‘sapping,' rather than by runoff of surface water," University of Colorado geologist Bruce Jakosky writes in Friday's issue of the journal Science. "Although this probably requires an ancient climate warmer than today's, it does not necessarily require an atmosphere warm enough to allow substantial atmospheric precipitation and runoff."

Those words echo the *view of Michael Malin, the principal investigator for the camera aboard the Mars Global Surveyor spacecraft now orbiting the planet.

Jakosky also points out that Global Surveyor's thermal emission spectrometer found a large concentration of hematite, an iron-bearing mineral that forms on Earth only in high-temperature aqueous systems. "This is compelling evidence for hydrothermal systems on Mars," he writes.      Such hydrothermal systems could have provided a suitable environment for the development of life on Mars, Jakosky says, and some form of life may continue to lurk there, if only on the microscopic level.

But how do you test those amazing hypotheses? One strategy is to take samples from those ancient valleys and flood plains, in the hope that you can reconstruct the geological and perhaps even the biological record. The recently launched Mars Surveyor 98 mission is designed to shoot *penetrators as far as 6 feet below the planet's surface, and there are other plans to dig and burrow for samples of subsurface soil.

[*Sarah Gavit, project manager for the Deep Space 2 microprobes, explains how the probes will be used during the Mars Surveyor 98 mission.] 

In the end, however, explorers may have to drill thousands of feet into Mars. Indeed, Farmer said that just might be the main justification for sending humans to Mars, perhaps sometime within the next 20 years.

Mars isn't the only world where scientists want to go deep: For example, researchers see ample evidence that a briny ocean lies miles beneath the icy surface of *Europa, one of Jupiter's moons. Such a body of water would be the No. 1 target in the search for life elsewhere in the solar system. Some scientists say even *Charon, Pluto's moon, might have a subsurface ocean. NASA's Jet Propulsion Laboratory already is testing *robots that might eventually burrow beneath the ice and sample those seas.

In all these cases, researchers will have to deal with the issue of forward contamination: How do you guard against transferring Earth's organisms to these otherworldly environments? Ruining your samples would be the least of your problems: You could ruin an entire global ecology in the process.

Avoiding such a catastrophe will require decades of planning, and an ability to handle the controls with surgical skill. Hmmm ... come to think of it, maybe a bandoleer-bedecked Bruce Willis type isn't the right person for the job after all.