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Ancient Mars Went Through Numerous Cycles of Life and Death

Mars has a checkered past of wetness and dryness.

Ancient Mars Went Through Numerous Cycles of Life and Death
An image of Mars from orbit, at sunrise. rajeshbac / iStock

With the recent landing of NASA's Perseverance lander, it's easy for attention to shift away from earlier craft still roaming the surface of Mars. But Curiosity, one such rover, is still exploring the base of Mount Sharp (also called Aeolis Mons) — which reaches several miles high from the center of the Red Planet's Gale crater.

An international team of researchers using the Curiosity rover on Mars discovered historical shifts in the Red Planet's climate between dry and wetter periods before it completely dried up roughly 3 billion years ago, according to a recent study published in the journal Geology.

Curiosity rover reveals cycles of life and death of varying climates

The researchers — comprised of a French-U.S. team led by CNRS Researcher William Rapin of the Institut de Recherche en Astrphysique et Planétologie — used Curiosity's ChemCam instrument to execute detailed observations of Mount Sharp's steep terrain from a distance. Orbital spacecraft had already offered hints about the mineral makeup of the slopes, but with ChemCam, the researchers successfully studied the sedimentary beds from the surface of Mars.

The analysis revealed the initial conditions of the local terrain when it first formed. Moving up the sedimentary beds, which are several hundred feet thick, the makeup of the bed varies drastically. Above the lake-deposited clays forming the base of Mount Sharp, the team observed wide, tall, cross-bedded structures — which imply the migration of dunes formed from wind during a long, dry climate phase. Higher on the mountain, the team saw thin beds alternating between resistant and brittle — which is generally normal for river floodplain deposits, and suggests a return to wetter environmental conditions.

This means Mars' climate likely had several large-scale fluctuations between river and lake coverage, and dry conditions, until the planet generally dried out into the arid world we see today. Curiosity is on an extended phase of its mission, and is slated to climb the foothills of Mount Sharp to drill into different types of beds. This new varying-weather model will be tested with evidence, with additional studies launched into how the climate underwent these shifts — all with the aim of furthering our understanding of these drastic shifts in climate.

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Mars was subject to intermittent periods of global warmth

This comes on the heels of another study in March, which showed that Mars had intermittent periods of warmth from the increased presence of greenhouse gases caused by volcanism and meteorites — opening the door for microbial life to potentially evolve in challenging environments subject to long frigid periods. The authors of the study stressed the need to reconcile the Red Planet's geology with models of atmospheric revolution, and this latest study using the Curiosity rover's data from Mount Sharp could be an early step in studying the ancient Martian atmosphere by examining various layers of sediment bed.

Scientists have learned much about Mars, but they're just getting started. With numerous rovers — including the recent Perseverance — preceding eventual plans to settle humans on the Red Planet, the next decade will likely see our understanding of Mars greatly expand into its history, and the ways it could support human activity in the coming centuries. But from the recent study, we can say: it may not be friendly to life now, but in the past, it might have been.

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