Nasa insists perchlorate doesn't rule out life on Mars

Samples containing perchlorate were found in and around the "Snow White" trench dug by Phoenix's robotic arm. NASA/JPL-Caltech/University of Arizona

Martian soil appears to contain perchlorate salts, according to the latest twitterings from Nasa's Phoenix Mars Lander. The presence of perchlorate generated rumours this week because of suggestions that it meant that the soil is less friendly to life than previously thought.

Not so, according to Michael Hecht of Nasa's Jet Propulsion Laboratory, who said that "finding perchlorates is neither good nor bad for life". However, he said different perchlorate salts have different properties that could "make us reassess how we think about life on Mars" if the finding were confirmed and perchlorate was found at other sites.

One possibility, for example, is that the soil samples were contaminated by perchlorates transported from Earth on the lander. Although the fuel of Phoenix itself contains no perchlorates, they were used in the boosters during launch.

Perchlorates are ions consisting of an atom of chlorine surrounded by four oxygen atoms. They are weak oxidants meaning that they tend to transfer oxygen atoms in chemical reactions. On Earth, organisms coexist with perchlorates in arid places such as Chile's Atacama desert.

Another Mars Phoenix scientist, Samuel Kounaves, confirmed that "it's a benign chemical in terms of most organisms". Some even use it to generate energy.

Last week, the Wet Chemistry Laboratory on the Mars lander found water in the soil by "tasting" it. Perchlorate was detected by Phoenix's Thermal and Evolved-Gas Analyzer (TEGA) "which has the ability to sniff it, and we hadn't done that yet", said Hecht.

Nasa has some animations of the laboratory and the analyser.

The Phoenix project took the unusual step of releasing these intermediate results: "We decided to show the public science in action because of the extreme interest in the Phoenix mission, which is searching for a habitable environment on the northern plains of Mars," said principal investigator Peter Smith.

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