This wonderfully elegant suggestion comes the University of Canterbury, New Zealand, where a group of geologists had an epiphany.
In research led by Christopher Oze (and published ealier this month in the Proceedings of the National Academy of Sciences of the United States of America), the team measured rates of methane and hydrogen production during a geological process called olivine hydrolysis, or serpentinization. The process occurs on Earth where the mineral olivine reacts with water to produce serpentine around hydrothermal vents.
It is well known that olivine and serpentine are also present on the Martian surface, suggesting similar water-mineral reactions have occurred below the Red Planet's surface. This also means methane and hydrogen are eventually vented into the atmosphere.
Oze's team carried out serpentine-production laboratory tests, a situation where no living organisms were present. They measured the resulting hydrogen:methane ratio. They then measured the hydrogen:methane ratio produced by hydrothermal vents in nature where living organisms were present.
On Earth, when microbes metabolize minerals for energy, they produce methane as a byproduct. Therefore, by measuring the ratio of hydrogen:methane where living organisms are known to be present and comparing those results with ratios measured in the lab (where no life was present), the fingerprint of microbial metabolism can be detected. Where there's life, there should be an overabundance of methane compared with hydrogen (creating a low hydrogen:methane ratio).
"From these experiments the hydrogen to methane ratio over time divided hydrothermal systems that did not involve living matter from those in which biota was present. This really gave us an ‘aha' moment where we realized this method could be used to look at life on other planets," said Oze in a press release.
HOWSTUFFWORKS: Life On Mars?
Measuring this ratio on Mars is well within our current technological capability, so all we need to do is to send a "sniffer" Mars robot to the Red Planet, sit it next to an ancient hydrothermal vent and command it to sniff the air.
Who knows, there might be a low hydrogen:methane ratio there, too.
Source: University of Canterbury
Image: A rendering of Kasei Valles, the largest channel carved by water on Mars, using THEMIS data from NASA's Mars Odyssey. Credit: NASA/JPL/Arizona State University, R. Luk.