Methane ‘smelt’ on Mars… but who dealt it?

Author: The Conversation / Source: The Next Web

The discovery of life on Mars would get pretty much everyone excited. But the scientists hunting for it would probably be happy no matter what the outcome of their search – whether life turned out to extinct, dormant or extant. They’d even consider finding no evidence of life whatsoever to be an important discovery.

But, as the saying goes, absence of evidence is not evidence of absence, and it will take many decades of detailed exploration of Mars to be reasonably sure that life has always been absent there.

There have been no direct observations of living organisms or fossils on Mars so far. But there are other types of evidence. One of the most often cited is the controversial detection of methane in the planet’s atmosphere, first in 2004 and then in 2014. This could have been produced by some kind of past or present microbial lifeform. However, the abundance is so low that the data remain uncertain. And in 2018, the team behind the European Space Agency’s Trace Gas Orbiter said they had failed to discover any methane.

Now a new paper, published in Nature Geoscience, reports a fresh detection of methane in the planet’s atmosphere, along with a theory of where it came from. But given how difficult it is to make reliable measurements of this gas, how confident can we be about the results?

Double detection

The new research used archived data acquired between 2012 and 2014 by the Planetary Fourier Spectrometer aboard Mars Express, which studies the composition of the planet’s atmosphere through the infrared radiation that is reflected and emitted by the planet. This is the same instrument that first detected low levels of methane in Mars’ atmosphere in 2004.

The difference between the two sets of observations comes from the mode in which the spectrometer operated. In 2004, the data were acquired by the instrument looking through the atmosphere to the surface as Mars Express orbited the planet. In…

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