What is the Mars Orbiter Mission

ExoMars: In Search of Life on the Red Planet

08/03/20169280 views21 likes

First publication of the text in Stars and Space (issue 3/2016).

Sunrise on Mars: 400 kilometers above the surface, a space probe in orbit directs its instruments towards the sunlight that streams through the planet's atmosphere.

She is looking for the spectral signatures of important gases such as methane, which can indicate biological or geological processes that are still active today. At the same time, a vehicle is on the surface using a drill to take the first soil sample from a depth of two meters. The vehicle is located in a region that was covered with liquid water in the early days of the planet around four billion years ago. Will it find remnants of past life that were protected from the high-energy radiation that floods the surface today?

For centuries mankind has been fascinated by the search for life on Mars, from artists and writers to explorers and astronomers. Although the above scenario looks like a scene from a science fiction novel, it will soon become a reality thanks to the ExoMars program.

ExoMars is a joint project of the European Space Agency ESA and the Russian space agency Roskosmos. It consists of two missions: the first, which started in mid-March 2016, includes the so-called Trace Gas Orbiter (orbiter for trace gases, TGO for short) and a landing module called Schiaparelli, which is intended to test the procedure for a soft landing on Mars.

The second mission, which will follow in 2020, consists of a Mars rover and a landing platform with scientific instruments. The main task of the ExoMars program is to answer the question of whether Mars was once animate or is still alive.

The researchers want to find out whether the planet is still geologically active today or whether evidence of simple microbial life can be found there. However, it was not that long ago that speculation about this really turned over and many people assumed that there was intelligent life on our neighboring planet.

The ExoMars module for the test landing is named after the Italian astronomer Giovanni Schiaparelli

These fantasies were reinforced by the misinterpretation of telescopic observations made by the Italian astronomer Giovanni Schiaparelli (1835-1910) towards the end of the 19th century: he had perceived light and dark straight lines on the planet, which he called "canali" in Italian. These were mistakenly translated as "channels" instead of "furrows" or "grooves" in English and other languages. This imposed the image of a network of irrigation canals that were supposedly built by intelligent beings on Mars.

The ExoMars module for the test landing is named after Giovanni Schiaparelli, the official name of which is otherwise “Entry, descent and landing demonstrator”, or roughly in German: “Module for demonstrating entry, descent and landing on the surface of Mars”.

After all, space probes photographed the surface of Mars in detail in the 20th century and cleared up the misunderstanding of the canals: the straight structures that Schiaparelli saw were only optical illusions. However, the scientists continued to believe that there could be microorganisms on Mars. In fact, in 1976 the US Viking program set out to search for metabolic products of microbes in the Martian soil using two landing probes with special instruments.

After this was unsuccessful, the researchers switched to a phased research strategy. It was already clear from observing the planet with the two Viking orbiters that water - the basic condition for the creation of life as we know it - had played a major role in shaping the surface of Mars. Indeed, ramified networks of valleys - similar to those formed by rainfall in the terrestrial deserts - and ancient dried-up river beds and channels indicated this.

This resulted in the mantra "Follow the water". But today the surface of Mars is cold, dry and exposed to strong radiation, so that organisms would not survive there. But could life have taken root on Mars billions of years ago during earlier humid environmental phases?

To this day, this remains one of the most important unsolved scientific questions of our time. It has spurred numerous missions to Mars since mankind began exploring the Red Planet. More than 40 space probes were launched in the direction of Mars, albeit with very different successes. Although our understanding of Mars has improved tremendously since then, we still have no answer to this core question.

More than 40 space probes have already launched towards Mars

Europe has been involved in numerous missions to Mars carried out by the US, Russia and Japan. The first mission of its own, Mars Express, began in 2003. It also carried the British Beagle-2 lander, which successfully separated from the mother probe, but then went missing.

Mars Express was designed to operate for two years in orbit around Mars, but is still active after more than twelve years. One of the most interesting observations in her impressive career was the detection of methane in the Martian atmosphere. This discovery was to become the nucleus for the development of the Trace Gas Orbiter (TGO) of the ExoMars program. On earth, living organisms in particular release a large part of atmospheric methane.

It is also the main component of natural gas; Another contribution comes from the volcanic and hydrothermal activity of our planet. Although methane makes up less than 0.000 18 percent of the gases in the earth's atmosphere (or 18 parts per billion particles per unit volume = 18 ppbv), several hundred million tons enter our atmosphere every year.

Since the biological activity of the earth plays a key role in methane production, the reliable detection of methane on Mars is a first important step in understanding the currently active processes that generate and remove this gas there. In the Martian atmosphere, methane should only have a very short lifespan of around 400 years, as it is destroyed by the sun's ultraviolet radiation. Mixing processes in the atmosphere should ensure that a more or less uniform methane content develops quickly at a low level. If this is correct, there should be a source that constantly replenishes the supply and, at the same time, a process that quickly removes the methane again. This is the only way to explain the observed changes in methane concentrations.

Understanding these processes is one of the most exciting goals of the Trace Gas Orbiter. You are a riddle to be solved. In fact, one of the main tasks for TGO is to analyze a large number of trace gases in the Martian atmosphere at the same time. They are only present there in small quantities and make up much less than one percent of the total composition. It is the relationships between the various trace gases that should give us insights into the possible origins of methane and other gases of interest, be it biological or geothermal in nature.

TGO also has the Schiaparelli test module with it, which will test key technologies with a view to the next mission of the ExoMars program, the ExoMars-2020 mission mentioned above.

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