Mars is too small to hold liquid water, study finds

Little water remains today in the ice caps and in the atmosphere of Mars, the fault, it seems, to a loss of water in space. But the red planet was doomed to desiccation because of its small size, suggests a new study.

Mars water
© Ittiz CC BY-SA 3.0

Thanks to the numerous observations of robotic explorers such as NASA’s Curiosity and Perseverance rovers, scientists know that liquid water has flowed on and under the Martian surface in the past. The Red Planet was once home to lakes, rivers and streams, and possibly even a huge ocean that covered a large part of its northern hemisphere.

Regrettably, this water almost completely disappeared about 3.5 billion years ago, lost in space. Scientists believe this is due to a dramatic climate change, which occurred after the loss of its magnetic field. The latter protected the air of Mars against charged particles from the sun.

But this immediate cause was underpinned by a more fundamental driver, according to a new study: Mars is just too small to retain surface water over the long term.

A planet “fundamentally too small to hold water”

« The fate of Mars was decided from the start Explains the co-author of this study, Kun Wang, assistant professor of Earth and planetary sciences at the University of Washington. ” There is probably a threshold for rocky planets to hold enough water for habitability and plate tectonics. »He adds. This threshold would exceed the size of Mars, scientists believe.

The team thus examined 20 Martian meteorites, selected in order to be representative of the global composition of the red planet. Researchers measured the abundance of various isotopes of potassium within these rocks, which ranged in age from 200 million years to four billion years.

See also: Mars: admire the planet in 3D thanks to this image captured by Ingenuity

With the help of potassium as a tracer, they discovered that Mars lost a lot more volatile elements (such as water) during its formation than the Earth, which is approximately nine times more massive than the red planet.

« This study highlights that there are a very limited size range so that the planets have just enough, but not too much water, so that they can develop a living area environment »Says Klaus Mezger, co-author of the study, which you can find here.

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