ExoMars detects almost no methane on Mars in a surprise result

One of the keys to exploring the red planet in search of present or past life is to understand the molecules that make up its thin atmosphere. Various missions have detected methane on Mars, considered as one of the distinctive signs of living organisms. The arrival of the ExoMars mission with its Trace Gas Orbiter (TGO) instrument allowed scientists to take the most accurate measurements possible to date for methane concentration. However, the first major release of data shows almost no gas in the Mars atmosphere. This is an unexpected result.

The TGO is the orbital part of the ExoMars mission. It is also the only part of the ExoMars mission now. Unfortunately, the Russian-made landing gear Schiaparelli failed to slow down with the landing thrusters because of a defective sensor. He crashed into the Martian landscape, leaving the TGO alone.

Fortunately, the TGO is the most sensitive atmospheric tool ever sent to Mars. It features a variety of infrared and ultraviolet spectrometers capable of sweeping the atmosphere in search of traces of gas. There is also a neutron detector for mapping water and hydrated minerals. It is in an approximately circular orbit 400 km above Mars, sniffing the atmosphere and counting the molecules. The first dataset from April 2018 to August 2018 shows almost no methane on Mars – a maximum of 0.012 parts per billion (ppb). This is far less than scientists expected rudimentary methane detectors Curiosity mobile.

There are some possible explanations for this result. Curiosity and other ground-based instruments may simply be wrong with regard to the concentration of methane on Mars, perhaps because of temporary short-term peaks in methane concentration. Alternatively, methane levels may be higher near the surface, but a process destroys the molecules before they reach an altitude where the TGO can detect them.

The ExoMars team is supportive of this latter explanation, but the process of methane decomposition is expected to be about 1,000 times faster than conventional chemistry in explaining the difference. The team proposed that methane be released into Martian rock and soil, or that it chemically binds to eroded quartz deposits.

This result does not necessarily mean that there is no trace of life on Mars, but it seems less likely that methane indicates the way. Missions like that of the future rover Mars 2020 still have many tracks to follow.

Now read: