Life On Mars: Have We Already Found It?

“Today, we do really have a lot of evidence pointing in the direction of life on Mars. I think it’s actually more scientifically outrageous to think that Mars is and always has been sterile.”

Seed Magazine’s Lee Billings discusses the prospect of finding life on Mars and elsewhere in the solar system with Dirk Schulze-Makuch, co-author of We Are Not Alone: Why We Have Already Found Extraterrestrial Life:

Here’s a brief excerpt on the Viking mission to Mars:

“In some ways the timing was bad for Viking. A lot of progress was made after its life-detection experiments were already on or on their way to Mars: The discovery of all the ecosystems at undersea hydrothermal vents, and the extremophile research of the early 1980s really changed how we think about life and its limitations. The Viking researchers thought life on Mars would be heterotrophic, feeding off abundant organic compounds distributed everywhere all over the Martian surface. That picture was wrong, and studies of extremophiles on Earth have made us think differently about Mars. Some people say Viking tried to do too much, too early, and as a result of its ambiguous results, nothing has happened with Martian life-detection experiments ever since.

“For the Viking results, the devil is in the details. There were three life-detection experiments: the Labeled Release Experiment that yielded a positive result, the Gas Exchange Experiment that gave a negative result, and the Pyrolytic Release Experiment, which was gave ambiguous, inconclusive results. Viking’s Gas Chromatograph Mass Spectrometer (GC-MS), designed to detect organic matter, was made the appeals judge so to speak—and since it did not detect any organic matter, it was concluded at that time that Viking did not detect life.

“However, the results of the GC-MS were always somewhat odd. This is because we know from the Martian meteorites that there are organics on Mars. Also, it’s been shown that the same instrument could not detect organics in the Dry Valleys of Antarctica or from hydrothermal soil, places on Earth where we know that a small but significant population of microbes makes a living. So the question is, why did the GC-MS not detect the organics present on Mars? Was the concentration too low? Were they in a form that was not detectable? Or, were they all oxidized to carbon dioxide before they could be measured as organics?

“We think the latter because an extra amount of carbon dioxide was exactly what the GC-MS detected. This would be nicely explained by a hypothesis I put forward along with my colleague Joop Houtkooper, which posits that Martian organisms could use a mixture of hydrogen peroxide and water as intracellular fluids rather than water alone. When heated during the GC-MS experiment, the hydrogen peroxide would have become unstable and oxidized all the organic compounds, releasing carbon dioxide.

“Such a hydrogen peroxide–water mixture would be a perfect adaptation mechanism for Martian organisms, because it would also convey antifreeze properties—down to – 56°C—and hygroscopicity, which is the ability to attract water molecules directly from the atmosphere, like honey or sugar does. That would be a huge advantage for any life on a very dry desert world such as Mars. And it would also explain the results of the Gas Exchange experiment and the Pyrolytic Release experiment. They were conducted with too much water. If you are adapted to the little water that is present on Mars, too much water will overwhelm you. It’s as if an alien race were to notice that one of us is dying of thirst, and then try to help us by placing us in the middle of the Pacific Ocean. We would drown. In a sense this may be what Viking did to Martian microbes. I think it is particularly telling that one of the Pyrolytic Release experiments conducted under dry conditions showed highly significant organic synthesis rates consistent with microbial life, while another one conducted under wetted conditions showed lower synthesis rates than even the sterilized control did.”

Published in: on April 22, 2010 at 2:58 pm  Leave a Comment  

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