Mars Finding Doesn't Rule Out Life
Wednesday, August 6, 2008
With reports circulating on the Internet that the Phoenix lander had found a chemical in the Martian soil that made past or present life there highly unlikely, NASA officials quickly organized a teleconference yesterday to announce that although they had made an unexpected discovery, it had little bearing on whether the planet ever supported life.
What the lander detected was perchlorate, a highly oxidizing and potentially toxic compound that is found on Earth in generally arid regions. The chemical, which is used in solid rocket fuels, air bags and fireworks, can harm the human thyroid gland by blocking the absorption of iodine.
But NASA officials said their consensus view is that the presence of perchlorate "probably comes down as a positive rather than a negative" in terms of the possibility of life on Mars, said Phoenix principal investigator Peter Smith of the University of Arizona in Tucson.
The perchlorate was first detected several weeks ago by the Phoenix instrument that moistens soil samples and analyzes the results. A second mini-laboratory, which heats the material collected by the Phoenix robotic arm, has not found the chemical, although the researchers said it had not yet really looked for it.
Perchlorate is commonly found in the Atacama desert of Chile, one of the driest places on Earth. While researchers long believed that life could not survive such extreme conditions, more recent studies have found microbes and other organic material living there. NASA often uses the Atacama as an "analogue" for conditions on Mars.
The Phoenix lander's instruments have confirmed the presence of water ice and nutrients needed for life, including sodium, potassium and magnesium. But no organic, or carbon-based, materials -- a signature of life on Earth -- have been found so far.
Smith and others emphasized that they were presenting preliminary data that had not been fully confirmed or peer-reviewed. But with the Internet buzzing with tales of a finding that precluded life on Mars, the NASA team wanted to present its quite different information.
NASA officials said they are also studying whether the perchlorate found in the soil could have possibly come from the fuel used to launch Phoenix, although they said the chances of such a contamination were very small.
Perchlorate is a chemical compound consisting of chlorine, hydrogen and oxygen, and often binds with sodium, magnesium and ammonia.