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. 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.
