Bringing Life to Mars; The Future of Space Exploration;
Scientific American Presents; by McKay; 6 Page(s) Four billion
years ago Mars was a warm and wet planet, possibly teeming with
life. Spacecraft orbiting Mars have returned images of canyons
and flood valleys-features that suggest that liquid water once
flowed on the planet's surface. Today, however, Mars is a cold,
dry, desertlike world with a thin atmosphere. In the absence of
liquid water-the quintessential ingredient for life-no known
organism could survive on the Red Planet. More than 20 years ago
the Mariner and Viking missions failed to find evidence that
life exists on Mars's surface, although all the chemical
elements needed for life were present. That result inspired
biologists Maurice Averner and Robert D. MacElroy of the
National Aeronautics and Space Administration Ames Research
Center to consider seriously whether Mars's environment could be
made hospitable to colonization by Earthbased life-forms. Since
then, several scientists, using clima