The Mars Phoenix lander discovered evidence of perchlorate (ClO4) and water ice in Martian soil, NASA researchers announced in August. Perchlorate, a highly reactive chemical that can occur naturally in arid areas such as Chile's Atacama Desert, was detected in two soil samples analyzed by Phoenix's wet-chemistry laboratory. Considered harmful to fetuses, perchlorate provides fuel for some microbes. For that reason, the discovery says little by itself about the possibility of life on Mars, NASA scientists say. Water ice was also identified in chunks of soil vaporized by Phoenix's gas-analyzing instrument. The result confirms 2002 observations by the Mars Odyssey orbiter, which detected ice in the form of subsurface hydrogen atoms at the planet's poles. In light of these successes, the space agency extended the Phoenix mission by five weeks, to September 30.
This article was originally published with the title "No Ruling Out Life" in Scientific American 299, 4, 36 (October 2008)