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Massive Mud Downpours Might Have Formed Some of the Most Ancient Highlands on Mars

mars helas dust

View of an area considered to be part of one of the oldest terrains of Mars, dating back to as much as approximately 4 billion years ago. The terrain’s landscapes include impact craters (e.g., white arrows) and water-carved channels (black arrows), which appear to have been extensively eroded by wind.

Muddy rains produced by giant impacts into a primordial glaciated Mars may have played a crucial role in the emplacement of kilometers-thick mudstones on Mars, according to a new paper by a team led by Planetary Science Institute Senior Scientist Alexis Rodriguez. 

These mudstones comprise the Solar System’s oldest known sedimentary rocks, according the paper “The Oldest Highlands of Mars May Be Massive Dust Fallout Deposits” ( published in Nature Scientific Reports.

PSI scientists Eldar Noe Dobrea, Jeffrey S. Kargel, David A. Crown, Kevin D. Webster, and Daniel C. Berman are co-authors on the paper.

Mars  preserves the Solar System’s oldest water-modified landscapes. Rivers and glaciers are known to have extensively excavated the planet’s earliest highlands, which date back to about 4 billion years ago.

“We found that impact craters and adjoining fluvially emplaced sediments in these ancient highlands were wind-excavated to enormous depths, in some cases more than a kilometer. Wind on Mars can only move sediments that are sand- or silt-sized and finer, so very fine-grained sediments must largely make up these parts of the highlands,” Rodriguez said.

“When wind moves large amounts of sand, it produces dunes, but dunes are absent in these wind-sculpted terrains, suggesting that they are made mainly of silt, and perhaps clay,” co-author Berman said. “The wind erosion of these surfaces took place recently and might still be happening.”

alexis mars helas dust close up 

Close-up view of the above image showing wind scouring on a crater rim (black arrow) and central peak (white arrow). The central peak is made up of rocks uplifted from otherwise buried materials, and its scouring by wind shows that the fine-grained composition likely exceeds the landscape’s relief.

July 26, 2020
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