On the Martian equator in a northern corner of the Valles Marineris is a box canyon called Hebes Chasma. In it is what appears to be an ancient lake bed that reminds Chris McKay, a planetary scientist at NASA's Ames Research Center near San Francisco, of frozen Lake Hoare in Antarctica, a place where ancient and completely unexpected mats of microbial life were found. Hebes Chasma is the first place on Mars that McKay would like to see explored because he believes that if life ever existed on Mars, its traces might still be there.
Mars might once have been warm enough for Hebes Chasma to have held a large body of water. If so, the lake would have made an excellent cradle for early life. Even after the planet cooled to sub-freezing temperatures, life may still have found a way to survive as it did in inhospitable places on Earth. The average temperature of Antarctica's "dry valleys," the home of Lake Hoare, for example, is -4 degress F. Not long ago, scientists believed that life could not possibly exist in such a place, but it does--under rocks, in frozen lakes, and deep inside permanently frozen earth. The same situation may have held true on Mars.
According to McKay, investigating such possibilities would require a level of exploration well beyond the abilities of even the most complex robots. A search for evidence of life in these places could only be conducted by sending human beings to Mars.
