Methane could be the first detectable indication of life beyond Earth
If life is abundant in the universe, atmospheric methane may be the first sign of life beyond Earth detectable by astronomers. Although nonbiological processes can generate methane, a new study by scientists at UC Santa Cruz establishes a set of circumstances in which a persuasive case could be made for biological activity as the source of methane in a rocky planet's atmosphere.
The case for methane as a biosignature stems from its instability in the atmosphere. Because photochemical reactions destroy atmospheric methane, it must be steadily replenished to maintain high levels."If you detect a lot of methane on a rocky planet, you typically need a massive source to explain that," said coauthor Joshua Krissansen-Totton, a Sagan Fellow at UCSC.
"One molecule is not going to give you the answer -- you have to take into account the planet's full context," Thompson said."Methane is one piece of the puzzle, but to determine if there is life on a planet you have to consider its geochemistry, how it's interacting with its star, and the many processes that can affect a planet's atmosphere on geologic timescales."
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