CM – The changing habitability of Mars was recorded by ancient dune fields in the Gale crater

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April 22, 2021

by Caroline Brogan, Imperial College London

Understanding whether Mars was once able to support life has been an important driving force for Mars research over the past 50 years. To decipher the ancient climate and the habitability of the planet, researchers look at the rock record – a physical record of the ancient surface processes that reflect the environment and the prevailing climate at the time the rocks were deposited.

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In a new article published in JGR: Planets, researchers from the NASA-JPL Mars Science Laboratory mission used the Curiosity Rover to add another piece to the puzzle of Mars’ ancient past by placing a unit of rock in the gale Crater investigated.

They found evidence of an ancient dune field that was preserved as a rock layer in the Gale crater and lay over rock layers that had been deposited in a large lake. The rock remnants of the dune field are now known as the Stimson Formation.

The results help scientists understand surface and atmospheric processes – for example, the direction in which the wind blew sand to form dunes – and possibly how The Martian climate evolved from an environment where there might be microbial life to an uninhabitable one.

By looking at the preserved rock layers using images collected by the Curiosity Rover, the researchers reconstructed the shape, direction of migration and size of the great dunes, also known as Draas, that occupied this part of the crater.

Imperial dune models created by Imperial researchers show that there are dunes adjacent to the central summit of Gale Crater – known as Mount Sharp – were on a wind-eroded surface at an angle of five degrees. The investigation also found that the dunes were compound dunes – large dunes that contained smaller dunes that migrated in other directions to the main dune.

Lead author Dr. Steven Banham of the Imperial Department of Earth Science and Engineering said, « When the wind blows, it transports grains of sand of a certain size and organizes them into piles of sand that we recognize as sand dunes. These landforms are common on Earth in sandy deserts such as the Sahara, the Namibian dune field and the Arabian deserts. The strength of the wind and its evenness of direction determine the shape and size of the dune, and evidence of this can be preserved in the rock record.

« When an excess of sediment is transported into a region , can climb the dunes during their migration and partially bury neighboring dunes. These buried layers contain a feature called « transverse bedding » that can give an indication of the size of the dunes. and the direction in which they wandered. By examining these transverse beds, we found that these layers were deposited by certain dunes that form when competing winds carry sediments in two different directions.

« It’s amazing that we can tell from the Martian rocks that Two competing winds drove these great dunes over the plains of Gale Crater three and a half billion years ago. This is one of the first evidence of variable wind directions – seasonal or otherwise. « 

The lower part of Mount Sharp is made up of ancient ones Lake sediments. These sediments accumulated on the lakeshore when the crater was flooded 3.8 billion years ago shortly after it was formed. Curiosity has spent much of the past nine years examining these rocks for signs of habitability.

Dr. Banham added, « More than 3.5 billion years ago this lake dried up, and the lake’s bottom sediments were exhumed and eroded to form the mountain in the center of the crater – today’s Mount Sharp. The flanks of the mountain are where we have found evidence that an ancient dune field formed after the lake, indicating an extremely dry climate. « 

However, the new evidence suggests that the old dune field may have provided less for life than previously accepted. Dr. Banham said, « The vast expanse of the dune field would not have been a particularly hospitable place for microbes, and the records left behind would rarely contain evidence of life if there were. »

« This desert sand represents a snapshot of time in the galley. And we know that lakes preceded the dune field – but we don’t know what lies above the desert sandstones further up Mount Sharp, it could be more layers deposited in dry conditions or it could be debris deposited with We have to wait and see. « 

With Rovers on Mars, researchers can explore the planet in greater detail than ever before. Dr. Banham added, « Although geologists have been reading rocks on Earth for 200 years, it has only been the last ten years that we have been able to read Martian rocks with the same level of detail as we have on Earth. »

Researchers continue to study Curiosity found rocks and are now focusing on the wind patterns recorded from dunes further up Mount Sharp. Dr. Banham said, « We are interested to see how the dunes reflect the broader climate of Mars, its changing seasons and longer-term changes in wind direction. Ultimately, this all relates to the main driving issue: to find out if life ever formed on Mars. » / p> An international team led by Imperial has found evidence of ancient dunes on Mars that could help explain the ancient surface conditions.

Understanding whether Mars was once able to support life was in the an important driving force for Mars research over the last 50 years. To decipher the ancient climate and the habitability of the planet, the researchers look at the rock record – a physical record of the ancient surface processes that reflect the environment and the prevailing climate at the time the rocks were deposited.

In a new one Article published in JGR: Planets, researchers from the NASA-JPL Mars Science Laboratory mission used the Curiosity Rover to add another piece to the puzzle of Mars’ ancient past by examining a unit of rock in Gale Crater.

They found evidence of an ancient dune field that was preserved as a rock layer in the Gale crater and lay over rock layers that had been deposited in a large lake. The rock remnants of the dune field are now known as the Stimson Formation.

The results will help scientists understand surface and atmospheric processes – like the direction the wind blew sand to form dunes – and possibly how The Martian climate has evolved from an environment where there may be microbial life to an uninhabitable environment.

By examining the preserved rock layers in images collected by Curiosity, the researchers reconstructed the shape, direction of migration and size of the large dunes, too Draas, who occupied this part of the crater.

Imperial dune models created by Imperial researchers show that dunes next to the central summit of Gale Crater – known as Mount Sharp – were eroded by the wind on one of them Surface at an angle of five degrees. The investigation also found that the dunes were compound dunes – large dunes that contained smaller dunes that migrated in other directions to the main dune.

Lead author Dr. Steven Banham of the Imperial Department of Earth Science and Engineering said, « When the wind blows, it transports grains of sand of a certain size and organizes them into piles of sand that we recognize as sand dunes. These landforms are common on Earth in sandy deserts such as the Sahara, the Namibian dune field and the Arabian deserts. The strength of the wind and its evenness of direction determine the shape and size of the dune, and evidence of this can be preserved in the rock record.

« When an excess of sediment is transported into a region , can climb the dunes during their migration and partially bury neighboring dunes. These buried layers contain a feature called « transverse bedding » that can give an indication of the size of the dunes. and the direction in which they wandered. By examining these transverse beds, we found that these layers were deposited by certain dunes that form when competing winds carry sediments in two different directions.

« It’s amazing that we can tell from the Martian rocks that Two competing winds drove these great dunes over the plains of Gale Crater three and a half billion years ago. This is one of the first evidence of variable wind directions – seasonal or otherwise. « 

The lower part of Mount Sharp is made up of ancient ones Lake sediments. These sediments accumulated on the lakeshore when the crater was flooded 3.8 billion years ago shortly after it was formed. Curiosity has spent much of the past nine years examining these rocks for signs of habitability.

Dr. Banham added, « More than 3.5 billion years ago this lake dried up, and the lake’s bottom sediments were exhumed and eroded to form the mountain in the center of the crater – today’s Mount Sharp. The flanks of the mountain are where we have found evidence that an ancient dune field formed after the lake, indicating an extremely dry climate. « 

However, the new evidence suggests that the old dune field may have provided less for life than previously accepted. Dr. Banham said, « The vastness of the dune field would not have been a particularly hospitable place for microbes, and the records left behind would seldom contain evidence of life if there were. »

« This desert sand represents a snapshot of time in the galley. And we know that lakes preceded the dune field – but we don’t know what lies above the desert sandstones further up Mount Sharp, it could be more layers deposited in dry conditions or it could be debris deposited with We have to wait and see. « 

With Rovers on Mars, researchers can explore the planet in greater detail than ever before. Dr. Banham said, « Although geologists have been reading rocks on Earth for 200 years, it has only been the last ten years that we have been able to read Martian rocks with the same level of detail as we have on Earth. » Rocks and now focus on the wind patterns recorded from dunes further up Mount Sharp. Dr. Banham said, « We are interested to see how the dunes reflect the broader climate of Mars, its changing seasons and longer-term changes in wind direction. Ultimately, this all relates to the main driving issue: to find out if life ever formed on Mars. » / p> The research was funded by the UK Space Agency and is part of preparation for the upcoming ESA ExoMars mission to explore Mars for signs of ancient life.

« A rock record of complex aeolian bed forms in a Hesperian desert landscape: The Stimson -Formation as exposed in Murray Buttes, Gale Crater and Mars « is published in JGR: Planets.

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