In a finding that has renewed talk about the possibility of life on Mars, NASA said Sunday that its Curiosity rover had detected "unusually high" levels of methane on the Red Planet.
Methane is an odorless, colorless gas that can be produced by simple geological processes as well as by microbes and other living organisms, so the new methane spike doesn't definitively prove that life exists or once existed on Mars.
"While increased methane levels measured by @MarsCuriosity are exciting, as possible indicators for life, it's important to remember this is an early science result," Thomas Zurbuchen, associate administrator for the science mission directorate at NASA headquarters in Washington, said in a tweet on Saturday.
NASA said Curiosity scientists needed more time to analyze the new findings and to conduct additional methane observations. A spokesperson for the agency declined a request for more information.
Curiosity has detected methane many times since its arrival on Mars in 2012, but this is the most the rover has ever detected: 21 parts per billion by volume. That's three times higher than the previous record, Nature reported, though far below atmospheric methane levels on Earth.
Major sources of methane on Earth include the production and distribution of fossil fuels; cattle and other domestic livestock, which produce methane during the digestive process; and the decomposition of waste in landfills and wastewater treatment plants.
The rover's laser spectrometer device detected the methane while the car-size rover was parked at the Teal Ridge site within Gale Crater, a 96-mile-wide dry lake bed that was created millions of years ago by an asteroid impact. Curiosity was sent to the crater in part because its watery past makes it a likely spot to find evidence of past life on Mars.
Previously, Curiosity detected carbon-containing moleculesin ancient sediments on Mars as well as seasonal shifts in the levels of atmospheric methane. In a commentary on those discoveries published last June in the journal Nature, Inge Loes ten kate, an astrobiologist at Utrecht University in the Netherlands, called the discoveries "breakthroughs in astrobiology."
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