ESA’s ExoMars Trace Gas Orbiter (TGO) has been in orbit around the planet Mars since 2016. It’s primary purpose is to search for small traces of gases in the Martian atmosphere. In particular, those that may indicate the presence of biological life! We’re still a long way off answering that big question, but the spacecraft has recently found unexpected traces of ozone and carbon dioxide. Perhaps we’re not as alone as we thought?
Like most astronomical exploration, TGO has to gain all its information using light. Telescopes and spacecraft can’t very often go directly to their subject (in this case, the Martian atmosphere). So, they have to look at it, taking readings and pictures. Thankfully, light comes in lots of different types, defined by its wavelength. Light with a shorter wavelength has high energy, and light with a longer wavelength has low energy. This allows scientists to categorise the light into different parts of the electromagnetic spectrum.
All these different types of light have different properties. For example, the light you use to see the world around you is called visible light. This only makes up a tiny part of the spectrum. You aren’t able to see the ultraviolet part of the spectrum, but you can still see its effects in your sunburn! These two types of light have different properties, and can therefore by used by astronomers to learn different things about objects. Sometimes they can even use different wavelengths to see through clouds and atmospheres that would otherwise obscure their view.
The Martian atmosphere has what appears to be an overabundance of methane. It’s hoped that TGO can help explain this. However, 2 new papers detail measurements by TGO’s Atmospheric Chemistry Suite (ACS) of the wavelength range where you would expect methane to be, with unprecedented results. Not only did they find methane, but also carbon dioxide and ozone. These are gases that have been tentatively detected by other spacecraft, but never definitively found in this range.
The Martian atmosphere is mostly made of carbon dioxide, but it also contains small amounts of other gases. Scientists are trying to build a picture of where each of the gases came from, so that they have an idea of what they might find where. This makes surprising discoveries like this one all the more exciting!
On Earth, methane is mostly produced by living organisms. It can also be produced geologically, but the most exciting thing is that methane is known to break down over about 400 years. This means that any methane we find now couldn’t have been produced before that. This simple fact supports the possibility of recent (or still living) life on Mars.
Although they may be surprising, each new discovery by TGO and the rest of the ExoMars program takes us one step closer to understanding our planetary neighbour. The more we can understand the Martian atmosphere’s composition and where those gases came from, the closer we are to answering that fundamental question: is there life on Mars?