By Alexandra Witze
NASA’s Curiosity rover has measured the highest level of methane gas ever found in the atmosphere at Mars’s surface. The reading taken last week at Gale Crater — 21 parts per billion — is three times greater than the previous record, which Curiosity detected back in 2013.
Planetary scientists avidly track methane on Mars because its presence could be a sign of life on the red planet. On Earth, most methane is produced by living things, although the gas can also come from geological sources such as chemical reactions involving rocks. Various spacecraft and telescopes have spotted methane on Mars over the past 16 years, but the gas doesn’t appear in any predictable pattern — deepening the mystery of its origin.
Curiosity has measured methane many times since it landed in Gale Crater in 2012. The level is typically low, often in the parts per trillion range, and seems to rise and fall as martian seasons change.
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