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Mars did not dry up at once – Mars climate cycled between dry and wet periods

Strata at the foot of Mount Sharp

A view from the “Kimberley” formation on Mars taken by NASA’s Curiosity Rover. The strata in the foreground dip towards the bottom of Mount Sharp, indicating the flow of water toward a basin that existed before the greater part of the mountain was formed. Credit: NASA / JPL-Caltech / MSSS

The perseverance rover has just come on March. Meanwhile, its forerunner Curiosity continues to explore the base of Mount Sharp (officially Aeolis Mons), a mountain several kilometers high in the center of the Gale Crater.

Using the telescope on the ChemCam instrument to make detailed observations of the steep terrain of Mount Sharp at a distance, a French-American team led by William Rapin, CNRS researcher at the Institut de Recherche en Astrophysique et Planétologie (CNRS / Université Toulouse III / CNES)[1], has discovered that the Martian climate recorded there alternated between dry and wetter periods before completely drying up about 3 billion years ago.

Hillocks on the slopes of Mount Sharp

View of hills on the slopes of Mount Sharp showing the different types of terrain that will soon be explored by Curiosity Rover and the ancient environments in which they formed, according to the sedimentary structures observed in ChemCam’s telescopic images (mosaics A and B ). Credit: © NASA / JPL-Caltech / MSSS / CNES / CNRS / LANL / IRAP / IAS / LPGN

Spacecraft in orbit around Mars had already given clues about the mineral composition of the slope on Mount Sharp. But now ChemCam has successfully made detailed observations of sedimentary beds from the planet’s surface, revealing the conditions under which they formed. As we move up through the observed terrain, which is several hundred meters thick, the bed types change radically.

Lying over the sweet-deposited clays that form the base of Mount Sharp, wide, tall, cross-coated structures are a sign of the migration of wind-shaped dunes in a long, dry climate episode. Higher up, thin alternately brittle and resistant beds are typical of river surface deposits, marking the return of wetter conditions. The climate on Mars therefore probably underwent several major fluctuations between dry conditions and river and lake environments until the generally dry conditions observed today took hold.

During its extended mission, Curiosity is scheduled to climb the foot of Mount Sharp and drill into its various beds. It will test this model, characterize in more detail how the ancient climate evolved, and possibly understand the origins of these great fluctuations.

Reference: April 8, 2021, Geology.
DOI: 10.1130 / G48519.1

This work was supported by CNES, the French space agency, to oversee the construction of the ChemCam instrument and operate it in conjunction with the Los Alamos National Laboratory (New Mexico, USA).


[1] The other team members work at the Laboratoire de géologie de Lyon: Terre, Planètes, Environnement (CNRS / ENS de Lyon / Université Lyon 1) and Laboratoire de Planétologie et Géodynamique (CNRS / Université de Nantes / Université d’Angers) in France; at UC Santa Cruz, US Geological Survey, California Insitute of Technoloy and Los Alamos National Laboratory in the United States.

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