May 14, 2021

Mars was not dried up in one go


View of the Martian hills in the foothills of Mount Sharp showing the terrain that will soon be explored by the Curiosity rover and the ancient environments in which they formed.

View of the Martian hills in the foothills of Mount Sharp showing the terrain that will soon be explored by the Curiosity rover and the ancient environments in which they formed.
POT

The weather of Mars alternated between dry and wetter periods, before completely drying out about 3 billion years ago, according to a study published in Geology on data from the Curiosity rover.

Spacecraft orbiting Mars had already provided clues to the mineral composition of the slopes of Mount Sharp (officially Aeolis Mons), a several-kilometer-high mountain located in the center of Gale Crater. But now, NASA’s rover observing instrument, ChemCam, has managed to make detailed observations of the sedimentary beds on the planet’s surface, revealing the conditions in which they formed.

Moving up the observed terrain, which is several hundred meters thick, the bed types change radically. Above the clays deposited by the lakes that form the base of Mount Sharp, the wide and tall structures of the crossbeds are a sign of the migration of the dunes formed by the wind during a long and dry climatic episode, as revealed by research led by William Rapin, CNRS researcher at the Institut de Recherche en Astrophysique et Planétologie (CNRS / University of Toulouse III / CNES), in France.

Higher still, thin beds, alternating between brittleness and strength, are typical of river floodplain deposits, and mark the return of wetter conditions. Therefore, it is probable that the climate of Mars suffer several large-scale fluctuations between dry conditions and river environments and lacustrine, until the generally arid conditions observed today were imposed, the CNRS explains in a statement.

During its extended mission, the ‘Curiosity’ rover is scheduled to scale the foothills of Mount Sharp and drill into its various beds. Will put this model to the test, will characterize the evolution of the ancient climate in more detail and possibly understand the origin of these large fluctuations.

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