From: LARRY KLAES (ljk4_at_msn.com)
Date: Wed Aug 06 2003 - 16:25:36 PDT
NASA comes up short in search for life in Chilean desert
By BYRON SPICE
August 6, 2003
The Atacama Desert of northern Chile may be the world's driest desert, but areas of it nevertheless teem with life. So why can't NASA scientists find life there?
True, a NASA-funded team of scientists who participated in an Atacama field experiment in April found plenty. They were pestered by flies, marveled at the variety of lichens growing on and under rocks and watched as vultures circled overhead, a sure indication that mice skittered nearby.
But counterparts at the space agency's Ames Research Center in Moffett Field, Calif., poring over photos and instrument data transmitted from the field scientists, never found anything they considered proof of life.
For this team of NASA and academic researchers, assigned to develop robotic technology for finding life on Mars, those results might seem unsettling. If they can't detect life known to exist 5,000 miles away in the Atacama, how could they hope to determine if life exists on an alien planet 35 million miles away?
The researchers, who gathered at Carnegie Mellon University in Pittsburgh last week for a three-day workshop, nevertheless were pleased to discover that what they were able to discern about the geology of the desert by remote sensing had closely matched what scientists on the ground observed.
The results were encouraging, considering this was the first field experiment in what will be a three-year project, said Nathalie Cabrol, a planetary scientist at Ames and lead scientist of the Life in the Atacama Project. William Whittaker of CMU's Robotics Institute is the project's principal investigator.
But a host of issues remain for the dozens of researchers who are building the robot and the life-sensing instruments, which must eventually mesh to become a machine capable of scientific exploration.
"If I see a bush in front of my rover, there's not too much to discuss," Cabrol said. But if life is sparse, more subtle or resembles nonliving features, how do researchers pick out the signature of life? What features might prove something is living? What combination of sensors is needed to detect that signature?
With two robotic rovers now hurtling toward Mars to search for signs of water, the development of life-sensing robots gains greater urgency in the planetary community. If Mars Exploration Rovers are successful in their quest when they land on the Red Planet in January, the logical follow-up mission would be a search for life.
"Mars is a dynamic planet, a water-enriched planet," said James Dohm, a planetary geologist at the University of Arizona who has spent years mapping it. Growing evidence that it is geologically active, with subsurface magma, suggests that water may not only be present as ice, but also as groundwater. And the combination of magma and water greatly enhances the prospects for finding life, he contended.
But no one knows how to prove life exists by remote sensing. And, as this year's Atacama field experiment underscored, even the human eye can be tricked in extreme environments.
Searching along the edges of the Salar Grande, an evaporated salt lake, the researchers came across numerous rocks covered by lichens - leaflike, crusty or stalklike organisms that are combinations of fungi and algae. But not everything was as it appeared, said Alan Waggoner, director of CMU's Molecular Biosensor and Imaging Center.
Some of the rocks appeared to be covered with bumpy, green lichens, he noted. But when field researchers scratched beneath the surface, they discovered salt. The lifelike bumps were simply salt that, through evaporation, had effloresced to form puffy mounds. The green outer layer turned out to be oxidized copper, which at some point had blown on top of the salt and been incorporated into it.
It will be months before NASA's latest robotic explorers reach Mars, but earthbound observers can get what should be the best view of the Red Planet in about 60,000 years at the end of this month, when Earth and Mars pass within 35 million miles of each other.
For more information, visit the Planetary Society's Web site: planetary.org/marswatch2003.
(Distributed by Scripps Howard News Service, http://www.shns.com.)
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