LIFE ON MARS

The red planet is a pretty lively place. In the last 12 months, orbiters, rovers and landers, as well as the scientists operating them, have spotted the scars of ancient raging rivers, felt the shudders of a Marsquake and uncovered evidence of liquid water deep underground. As we discover more about the red planet’s tantalisingly Earth-like story, one question still persists: is there, or has there ever been, life on Mars? Here’s everything we know so far…

- DR STUART CLARK

A GASSY ENIGMA

ARE MARTIAN MICROBES BELCHING GAS INTO THE PLANET’S ATMOSPHERE?

In March 2004, ESA’s Mars Express mission confirmed that methane gas was present in the Martian atmosphere. The amount of methane was small, but its discovery was extraordinary, because on Earth, although some methane in the atmosphere comes from volcanoes, most of it is produced by living organisms. Methane only survives in the Martian atmosphere for a few hundred years, meaning that whatever was producing it was (geologically speaking) recent.

Although the volcanic explanation would be fascinating because Mars was thought to be geologically dead, the biological origin is what grabbed people’s attention. The methane seen by Mars Express was concentrated in certain regions and quickly dispersed to levels that could no longer be detected.

Then, a decade later, the methane returned. This time it was detected by NASA’s Mars Curiosity rover, which had landed in Gale Crater in 2012. Using its onboard Sample Analysis at Mars (SAM) instrument suite, the rover took a dozen readings over a 20-month period, mostly revealing extremely low levels of the gas. However, in late 2013 and early 2014, methane levels rose sharply by a factor of 10.

“At this point we don’t know the origin of this methane,” said NASA’s Danny Glavin, a participating scientist in the Curiosity mission, at the time. The same remains true to this day. Most recently, a re-analysis of Mars Express data has shown that it too detected methane in Gale Crater in June 2013.