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New NASA rover Perseverance is supposed to search for life on Mars

Mars is an inhospitable planet - but that wasn't always the case. About 3.5 billion years ago a dense atmosphere protected Mars from the merciless UV radiation of the sun, liquid water made its way on the surface, the temperatures were milder than today. In other words: The conditions on our neighboring planet once resembled those on Earth - they were life-friendly. But as the earth bloomed and produced ever more complex life, Mars turned into a cold, sterile desert world.

Scientists have long been concerned with what exactly happened to our outer neighbor. Two unanswered questions in particular are still in focus today: Did life originate on Mars in its prime? And if so, could there be a niche somewhere on the planet that it persists in to this day?

Delicate maneuver

Three new space missions launched into space last summer in search of new answers. One of them is about to take place tomorrow, Thursday, for their most delicate maneuver: Around 10 p.m. Central European time, the Mars rover Perseverance of the US space agency NASA is due to land on the red planet after a six and a half month journey. Nasa has successfully made it to the Martian soil nine times. With Perseverance, in German "Perseverance", your largest and most powerful Mars vehicle to date will now explore the planet. It is the declared main aim of the mission to find traces of life.

Ground steeped in history

"The fantastic thing about Mars is that you can look back much further into the past than on Earth," says Manuel Güdel. The Swiss astrophysicist, who has held a professorship for astronomy at the University of Vienna since 2010, compares the planet to a history book. "You can look back four billion years, that has to do with the modest erosion." Unlike the earth, which has changed dramatically over time due to water, wind and biological activities, the surface of Mars has remained much more pristine, explains Güdel.

The sediments contain traces from the early days of the planet that tell fascinating stories: of meteorite impacts and collisions with smaller bodies that could have brought about the building blocks of life, but also of rivers and lakes that once covered what is now the dust-dry Martian soil .

Unstable neighbor

The instability that gave Mars its present-day appearance is also inscribed in the landscape. The dried up river valleys and lake floors show that the life-friendly window of time on Mars was comparatively short. Some estimates suggest that the water might disappear from the surface after a few hundred thousand years. Today it still exists underground in the polar regions - how much is unclear.

"Compared to Earth, Mars has a few problems: It is smaller and has less gravitational pull, which also makes it more difficult to hold an atmosphere," says Güdel, who and his team are researching the momentous loss of the planet's dense gas envelope. Interactions between the upper atmosphere and the solar wind, but also strong ultraviolet radiation, were also involved in the degradation of the Martian atmosphere; the disappearance of a global Martian magnetic field may also play a role.

Crater with potential

Not only did the atmosphere become thinner and thinner, gradually there was also no stopping water: under UV radiation, water vapor splits into hydrogen and oxygen - and hydrogen is so light that it quickly disappears into space. "Mars simply has too few protective mechanisms, its atmosphere has probably collapsed by a factor of 100 over time," says Güdel.

Until then, however, the conditions for life to emerge on Mars were likely favorable - the big question is whether something has gotten off the ground. The new NASA rover is supposed to look into a particularly interesting terrain: Its landing site is in a place that was once completely under water. Perseverance is said to land in the Jezero crater in the northern hemisphere of the planet that once housed a huge lake.

Searching for traces in the river delta

"The geology in this crater is exceptionally well preserved," says Briony Horgan of Purdue University in Indiana. The geologist is on the scientific team of the Mars mission and raves about the conditions in the crater. Thanks to images from space probes, it was possible to identify an extensive river delta in which a particularly large number of sediments are likely to have deposited, which the water carried over long distances. "There could be traces of organic molecules or even life in these deposits." The investigation of minerals also promises more precise information about the former conditions in this lake - for example about the composition of the water and the water level.

With the help of a radar, Perseverance could also find underground water reservoirs, if there are any. If there are still Martians today, it would be obvious that they have also retreated below the surface. Because the Martian soil is continuously sterilized by UV radiation, life as we know it would not survive that. Not even microbes. Like its predecessors, Perseverance is equipped with a drilling tool, but it is not designed for very deep holes.

Premiere for helicopter drones

The rover, which weighs around a ton, is a compact research laboratory on wheels for this purpose. It has seven scientific instruments and a sophisticated camera system that serves the mission in orientation and the search for promising geological structures. Technology from Austria is also involved in the 3D evaluation of this data: the Joanneum Research research institute in Graz and the Vienna Center for Virtual Reality and Visualization VRVis have jointly developed a software tool that enables interactive analyzes.

Another aid should also make the Mars rover's work on the planet a little easier, although it is primarily a test. Perseverance has a small helicopter drone called Ingenuity with them, which is supposed to make a few short flights and photograph the area around the rover from above. That could improve route planning - but above all, if successful, it would be the first time an aircraft takes off from another planet. In the extremely thin Martian atmosphere, a drone flight is an enormous challenge, and Ingenuity is to prove its feasibility for the first time.

Sample return planned

Another premiere is planned. The most interesting material samples from the Martian crater are to be collected in special containers and deposited at a convenient place for later collection. Together with the European Space Agency Esa, NASA plans to bring Mars material to earth for the first time in the early 2030s. The time-consuming return mission is not yet finally on the rails, but the technical planning has long been underway. NASA also sees this as an opportunity to test new technologies for future astronaut missions to Mars.

There are still many problems to be solved before humans can actually reach the red planet. Apart from the enormous medical risks, landings on Mars are generally one of the greatest challenges in space travel. The thin atmosphere makes it difficult to brake on the landing approach; multi-part braking systems are required to bring a spacecraft safely to the surface. The landing must also be completely autonomous, the distance between Mars and Earth is far too great for direct control.

Rush to Mars

The mixed results of the previous Mars missions also testify to these technical challenges: of 18 landing attempts, only ten were successful - nine of them were made by the USA. With Perseverance, NASA relies on a tried and tested maneuver that already proved its worth in 2012 when the Mars rover Curiosity landed.

In just a few months, China also wants to make its first attempt and bring a lander from the Tianwen-1 mission to the Martian soil. Beijing cites research into the topography and geological composition of the red planet and its internal structure as goals. Compared to NASA, however, the Chinese space agency CNSA is keeping a low profile on the details of the process.

A third visitor arrived on Mars last week: Al-Amal, the first Mars probe in the United Arab Emirates, is to explore the climate of the Red Planet from an orbit and help to better understand the eventful history of our neighboring planet. (David Rennert, February 18, 2021)