Research is sure of that once there was water on Mars. But today there is nothing left of it. Now a study finds a possible reason for this.
St. Louis / Frankfurt – When the planet Mars is explored, it is mostly about water and closely related to the question of whether the red planet once housed life. In the eyes of research, both belong together: where there is no water, life, as mankind knows, has a hard time. The fact that there was once water on Mars is undisputed in space research – but why it disappeared is unclear. In a study, researchers have now developed a new theory that could also have an impact on the search for habitable planets in space.
The researchers led by Kun Wang from Washington University in St. Louis, USA, are certain: “The fate of Mars was decided from the start.” The research team examined Mars meteorites for volatile elements such as potassium, among other things. It turned out that there are fewer volatile potassium isotopes in the meteorites from Mars compared to Earth than on Earth – but more heavy isotopes were found. From this, the experts concluded for their study, which was published in the journal Proceedings of the National Academy of Sciences: Mars lost the volatile components – and water is even more volatile than light potassium isotopes – very early.
Mars: is the planet too small to hold water on the surface?
During their work, the researchers found that there is a connection between the size of a celestial body and its potassium composition. “This is a new discovery with important quantitative implications for when and how the differentiated planets have absorbed and lost their volatile substances,” said Katharina Lodders, who also conducts research at Washington University in St. Louis and is co-author of the study.
“There is likely a threshold for the size requirements of rocky planets to store enough water to enable habitability and plate tectonics,” Wang explains in a statement from his university, and continues: “The mass exceeds that of Mars.” So Mars is too small to store enough water, the researchers conclude.
Mars: “Undisputed” that there was once liquid water on the surface
It is “undisputed that there was once liquid water on the surface of Mars,” emphasizes Wang. However, it is difficult to determine the amount through remote sensing and rover missions alone. “There are many studies of the amount of water on Mars, in some of which early Mars was even wetter than Earth. We don’t believe that, ”explains Wang. In fact, the NASA rover “Perseverance” has only just found out that its landing site on Mars, the Jezero crater, was once a well-filled lake that was fed by a river.
The research by Wang’s team relates specifically to the planet Mars, but it should also have an impact on the search for life on other planets outside the solar system, the researchers believe. So far, when looking for exoplanets that could harbor life, particular attention has been paid to whether they are in the so-called “habitable zone” of their star. What is meant is the distance to the star at which liquid water is possible. In the future, the size of the planets should also be taken into account, says Wang. His co-author, Klaus Mezger (University of Bern), is certain: “These results will guide astronomers in their search for habitable exoplanets in other solar systems.”
Was there life on Mars once? This question is still unanswered
This is also what Wang sees: the size of an exoplanet is easy to determine. “Based on its size and mass, we now know whether an exoplanet is a candidate for life, because a determining factor for the storage of volatile substances is its size,” explains Wang.
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However, this would still not clarify whether there was once life on Mars. In order to answer this question, the NASA rover “Perseverance” is currently exploring Mars. The rover has already taken the first rock samples from the red planet, examined them and stored them for future transport back to Earth. By then, at the latest, experts will be able to directly examine material from Mars for the first time – and possibly answer once and for all the question that has haunted them for so long: Was there once life on Mars?
Later on, human missions to the red planet could continue research on site. Humans could fly to Mars for the first time in the 2030s – were it not for problems such as radiation on Mars, which is fatal for humans in the long term, or the fact that humans can hardly take resources with them and have to use the resources of Mars instead. (tab)