NewsNew study: Is Mars too small to store water?

New study: Is Mars too small to store water?

Researchers are certain that there was once water on Mars. 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, the topic of water is often discussed and closely related to the question of whether the red planet was once home to life. In the eyes of research, both belong together: Where there is no water, life as known to mankind has a hard time. The fact that there was 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.” Among other things, the research team examined Martian meteorites for volatile elements such as potassium. 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 discovered 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 absorbed and lost their volatiles,” said Katharina Lodders, who also researches at Washington University in St. Louis and is a co-author of the study.

“There’s probably a threshold for the size requirements of rocky planets to store enough water to allow for habitability and plate tectonics,” Wang said in a statement from his university, continuing, “The mass exceeds that of Mars.” So Mars is too small to store enough water, the researchers conclude.

Der Mars ist heute staubtrocken, doch einst muss es Wasser gegeben haben. Diese Aufnahme des Nasa-Rovers „Opportunity“ zeigt mutmaßlich ein ausgetrocknetes Flussbett.


Mars is bone dry today, but once upon a time there must have been water. This image taken by NASA’s Opportunity rover probably shows a dried-up river bed.

Mars: “Indisputable” that there was once liquid water on the surface

It is “undisputed that there was once liquid water on the surface of Mars,” Wang emphasizes. However, it is difficult to determine the amount by remote sensing and rover missions alone. “There are many studies on the amount of water on Mars, in some of them early Mars was even wetter than Earth. We don’t think so,” Wang continues. In fact, NASA’s Perseverance rover has only just discovered that its landing site on Mars, Jezero Crater, was once a well-stocked lake fed by a river.

Although the research by Wang’s team relates specifically to the planet Mars, the researchers believe it should also have an impact on the search for life on other planets outside the solar system. So far, when searching for exoplanets that could harbor life, the main focus has been on whether they are in the so-called “habitable zone” of their star. What is meant by this is the distance from the star at which liquid water is possible. In the future, one should also include the size of the planets, 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? This question is still unresolved

This is how Wang sees it: The size of an exoplanet is easy to determine. “We now know whether an exoplanet is a candidate for life based on its size and mass, because a determining factor for storing volatile matter is its size,” Wang explains.

However, that still doesn’t explain whether there was life on Mars. In order to clarify this question, the NASA rover “Perseverance” is currently exploring Mars. The rover has already taken initial 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 examine material from Mars directly for the first time – and possibly answer once and for all the question that has been bothering them for so long: Was there life on Mars?

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Later, human missions to the red planet could continue on-site research. In the 2030s, humans could fly to Mars for the first time – were it not for problems such as the radiation on Mars, which is deadly for humans in the long term, or the fact that humans can hardly take any resources with them and instead have to use the resources of Mars. (tab)

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