Today it is a hostile desert planet – but it is now certain that the Martian surface was once also shaped by liquid water. The NASA rover “Perseverance” will soon find out whether there were any living beings on our neighboring planet at the time. A study has now confirmed that the planned destination is well suited for searching for clues. It is therefore a former river delta that, according to the new model, has developed in a way that has made it possible to preserve traces of potential life forms.
Are there or were there once beings on Mars? This is one of the most exciting questions when researching our neighboring planet. It cannot be ruled out that microbial life forms still exist today in the potentially humid depths. But the questioning gaze is currently focused primarily on the youth of Mars. Geological features indicate that there was still liquid water on the surface of the planet about 3.5 billion years ago. Over time, however, this water treasure mostly escaped into space or seeped into the underground.
In the time when Mars offered life-friendly conditions, the first unicellular organisms appeared on Earth. This raises the question of whether this development also took place in parallel on our neighboring planet. The Mars rover “Perseverance” is to investigate as part of the NASA mission “Mars 2020”. In the summer of this year, a rocket is to take the exploration vehicle to the red planet. In addition to analyzes on the surface of Mars, it is also planned that Perseverance will collect rock samples, which will then be brought back to Earth through a later return campaign.
Is the study area well chosen?
Initially, various locations were discussed as the target for the mission. NASA finally decided to go to an area in the Jezero crater on Mars. It is assumed that the remnants of a former river delta can be seen there. This seems useful for the search for traces of life forms. Because it is known from Earth that the comparatively rapid deposition of sediments in delta structures means that evidence of life is particularly well preserved underground. However, as the researchers led by Stanford University’s Mathieu Lapôtre report, it has so far been unclear how long it took for the sediment layers to form in the river delta in the Jezero crater. “The timing of processes is often a big unknown on Mars,” says Lapôtre.
He and his colleagues have therefore now developed a model of delta formation in the Jezero crater. One of the foundations was satellite images of the area. In their simulation of the characteristics of the former
In addition to information about the gravitational conditions on Mars and assumptions about the former climate, the researchers integrated a new system into the river system: Rivers, on the banks of which no plants grow, shift their beds about ten times faster than rivers with vegetation. This important information came recently from studies of a river bed in a dry area in the US state of Nevada.
Sediment layers with potential signs of life
As the scientists report, their model simulations showed that the delta formation in the Jezero crater occurred over the course of several hundreds of thousands of years. As the researchers explain, the river bed was not bubbling continuously. In the dry Martian climate 3.5 billion years ago, it was estimated that there was a water flow once every 15 to 30 years that lasted only about a day. The bottom line could have been a total time of active delta formation of 20 to 40 years.
However, as the scientists explain, under vegetation-free operations on Mars, this was sufficient to cause significant relocation of the river bed and thus stratification of sediments. “Our results show that the sediments settled quickly and that if there were organic matter, they would have been buried quickly,” says Lapôtre. In other words: If there were once microbial life forms on the surface of Mars, the river in the Jezero crater could have carried away their traces and protected under sediments. Thus, the results confirm the area as a good target for the extraction of rock samples, the scientists sum up.
“The mission is to produce the first samples that will be brought from Mars to Earth for investigations. It is very exciting! ”Says Lapôtre. “Because this could give you the chance to gain insight into the origin of life on another planet and thus into the question of what life is,” says Lapôtre.
Source: Stanford School of Earth, Energy & Environmental Sciences, professional article: AGU Advances, doi: 10.1029 / 2019AV000141