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Mysterious Mile-High Mounds on Mars Are Finally Explained

Located near the Mars’ equator, south of Elysium Planitia is a crater with mysterious mounds that have defied explanation … until now.

When NASA’s Viking program spotted mile-high mounds on Mars in the 1970’s, little did they realize what they were seeing. New research indicates that these formerly water-filled craters were covered up with dirt and dust by dry wind.

The Surface of Mars with Visible Craters

The Surface of Mars with
Visible Craters

MacKenzie Day, a graduate student at the University of Texas at Austin Jackson School of Geosciences, is lead author of a new study showing how the mounds were formed. Day says,

We went from a filled crater layer cake to this mounded shape that we see today.

Day and colleagues drew this conclusion after running a series of experiments. They created a mini-crater on earth, 30 centimeters (12 inches) wide and 4 centimeters (1,6 inches deep), filled it with damp sand and placed it in a wind tunnel. They observed how the wind shaped the sand until it was blown away. They used large-eddy simulation (LES) flow modeling to explore wind erosion patterns within the filled craters.

Mars mounds in different stages of evolution (top) compared with a model of that evolution built in a wind tunnel (bottom). Warmer colors indicate higher elevations.

Mars mounds in different stages of evolution (top) compared with a model of that evolution built in a wind tunnel (bottom). Warmer colors indicate higher elevations.

They took photographs for comparison with the Mars craters. This research was backed up by a computer model, showing the wind’s movement through the crater is it progressed through various stages of erosion. The mound’s structure showed water-borne sediments on the bottom with wind-borne sediments on top.

The study states,

Over the time scale of Martian geologic history, the role of craters in the sedimentary cycle of Mars has changed. Craters have evolved from being basins that served as sedimentary depositories trapping subaqueous and then aolian sediment, to sediment source areas from which sand and dust are eroded and then transported out of the craters. The juxtaposition of subaqueous strata and the audity of modern Mars invoke a dramatic change in planetary conditions.

This research shows evidence of a warmer and wetter Mars in the past. Analysis of 30 mounds on Mars sets their deposition to the Noachian period 3.7 billion years ago. The Noachian is believed to be the boundary period between Mars’ wet past and dry present.

Mars

Mars

The study adds,

The location of these mounded sedimentary deposits on Noachian terrain has implications for the timing of global climatic change on Mars and a restructuring of the Martian sedimentary cycle.

The reason why Mars underwent such a drastic climatic change remains a mystery.