Paris (AFP)
About 3.5 billion years ago, the water of the lakes and rivers of the planet Mars evaporated "due to climate fluctuations," according to a study published Monday in Nature Geoscience.
It is widely accepted that the red planet has possessed in the past abundant water in liquid form, with lakes, rivers and even perhaps a vast ocean that covered most of the northern plains of the planet. But this liquid water has disappeared without really knowing why or how.
To find out more clearly, William Rapin of the California Institute of Technology in the United States and his co-authors studied data from the Curiosity American rover collected in 2017 in the Gale crater, which is about 3.5 billion years old.
"A crucial moment in the history of Mars," according to the study. "We know that during this period the environment of Mars was changing radically and its atmosphere was actively eroded by the solar wind," says William Rapin. "We are convinced that this has profoundly altered its climate," adds the researcher.
But the analysis of hundreds of meters of distinct geological layers carried out in the crater of Gale "highlights the intermittent presence of salt deposits in the sedimentary rock", suggesting the existence of periods of strong evaporation of water to that time.
"We discover a reality made of climatic fluctuations, between wet and dry periods, which informs us at the same time on the types of ions available in the liquid water which flowed on the surface, and also on the type of changes that life would have had to face if it existed on Mars in those times, "concludes William Rapin.
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