The methane that once existed on Mars appears to be missing now and scientists are baffled. While the Mars Express orbiter showed that there were traces of methane in the red planet’s atmosphere back in 2004, according to findings by a European satellite, it all appears to have vanished now. If it does turn out that there is no longer any methane on the red planet, this could spell bad news for the microbes that scientists thought might be creating this gas.

As Science Magazine reports, the Mars Express orbiter measured the level of methane on Mars at 10 parts per billion (ppb), and some scientists have now suggested that the instruments on this spacecraft may not have had the right amount of sensitivity to have accurately gauged the precise amount of methane present.

However, the NASA Curiosity rover also detected methane at 7 ppb when it was perched in the Gale Crater of Mars, and this presence continued for many months after it was discovered. After this, scientists found that there was something called a minute seasonal cycle which led to the measurement of 0.7 ppb of methane during the summer in the north of the planet.

In an effort to better understand what is going on with this mysterious methane on Mars, in 2016 the European Space Agency’s Trace Gas Orbiter (TGO) devotedly scanned the atmosphere of Mars for this gas. Belgian and Russian instruments were created so that even extremely low amounts of methane could be picked up, but as NOMAD’s principal investigator Ann Carine Vandaele has noted, “We already know we can’t see any methane.”

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