New devices seek to find mineral links in hunt for life

SIGNS OF LIFE: Second of a three-day series

ASU's infrared camera on Mars Global Surveyor hasn't spotted the kind of water-formed minerals that life-hunting astro-biologists get most excited about. There are three plausible explanations.

Either those minerals aren't there, they are covered by dust, or Arizona State's thermal emission spectrometer doesn't have keen enough vision to spot them.

TES hasn't seen dried up lakes like the Death Valley playas, and it hasn't found mineral evidence for Yellowstone-like hot springs.

It hasn't spotted a trace of the carbonates or salts that would support the ancient-ocean theory, though it did find hematite, a mineral that on Earth usually forms in water.

``The idea was that TES was going to turn on and find all these carbonates and salts, and it was going to prove that we had sea floors. And they didn't,'' said William K. Hartmann of Tucson's Planetary Science Institute.

``My own interpretation is that these lake beds really are there, but over most of Mars, most of time they're covered over by all this dust,'' said Hartmann, a member of the Global Surveyor science team.

Maybe those deposits are exposed in places, but TES's vision is too blurry to see them.

To determine the level of image sharpness needed to see minerals of interest on Mars, Arizona State University's Jack Farmer and NASA post-doctoral researcher Jeffrey E. Moersch visited Death Valley recently.

TES can't see anything smaller than five miles across, said Philip Christensen, head of the Arizona State team that designed the instrument for NASA.

While the orbiting spectrometer would be able to detect a Yellowstone-sized hot-springs complex, anything smaller than the city of Tempe would be missed, he said.

But a next-generation version of the Arizona State infrared spectrometer, called THEMIS, will orbit Mars on a probe scheduled for launch next year. It will be able to see surface features the size of a football field.

Will that increased resolution be enough to reveal key minerals? No one knows for sure, and that's what Farmer and Moersch were testing at Death Valley.

They obtained infrared aerial photos of Death Valley's Badwater Basin from a plane that flew over the site at 25,000 feet.

The digital images were then manipulated to simulate the approximate resolution that TES and THEMIS can deliver from Mars.

Then the researchers drove into the basin for ``ground truthing,'' using a hand-held spectrometer to determine what minerals are present.

One stop was a playa near an old borax mine southwest of Badwater, the lowest spot in the United States at 282 feet below sea level.

Farmer and Moersch used a hand-help Global Positioning System receiver to find their location on the aerial photo to within 100 feet.

By comparing what's on the ground to what's seen in the aerial view, they learn the limits of the orbiting spectrometers - what they'll be able to detect and what they'll miss at Mars.

That, in turn, tells them the resolution they will need to identify potentially micro-fossil-bearing minerals from orbit during future missions.