NASA's Mars Reconnaissance Orbiter (MRO) has captured stunning images of almost perfectly round sand dunes on the surface of the Red Planet. While sand dunes of all shapes and sizes are common on Mars, circular dunes like these are a rare sight.
The dunes appear as slightly asymmetrical splodges in the picture, which was taken on Nov. 22, 2022, in Mars' northern hemisphere by the University of Arizona's High Resolution Imaging Experiment (HiRise) (opens in new tab) camera. The steep sides of the dunes are slanted southward, which might be due to Martian winds blowing the sand in that direction, planetary scientists at the university said in a statement (opens in new tab). They are unsure what caused the dunes to be so near-perfectly circular, however.
The image is part of a series taken by HiRise to help monitor how frost melts on Mars at 60 different locations as the northern hemisphere of the planet reaches the end of its winter season. Like Earth, Mars experiences a cycle of the 4 seasons of summer, spring, fall and winter. While the round sand dunes appear ice-free in this picture, a previous image showed them covered in frost.
HiRise, which is mounted on the MRO spacecraft, has been orbiting and surveying sand dunes on Mars since 2006 to help scientists understand how they move and how the weather patterns shape them. Data from the high-resolution camera indicate that sand dunes are migrating from the equator to the poles at a rate of up to 3.3 feet (1 meter) per Martian year, or 687 days on Earth.
Researchers are also using HiRise to study glacier-like formations and deposits at the base of slopes across Mars, which scientists think may once have been rich in ice, although the source of this ice remains a mystery, according to NASA (opens in new tab).
The MRO's primary mission was to search for traces of water on Mars. While this mission ended 12 years ago on Dec. 21, 2010, the spacecraft still serves as a communications bridge back to Earth for other Mars missions and continues to relay surprising images captured by HiRise: The camera also recently spotted rocks that look just like a teddy bear.
Following the story about Mars and it's 'round 'sand dunes:
Looking to our own earth for the answer, we can take the Extreme Winter Temps and How the Drift Form in Minnesota as an example. In my time spent in that Freezer .
On one winter's night when I had to be out and returning with a howling wind following my car, I encountered drifting Snow and Dirt building Drifts across my path. At one bridge I had to step on the gas to burst through a 'wall of Snow' that 'matched the opening of the bridge . I had no means of knowing just how thick this wall of snowpack was or what was hidden on the other side but there was no time to stop or go around it. There was no stopping or I'd be stuck . As i hit the 'wall' it turned out to be only about 12 inches thick and nothing was waiting for me as the packed snow fell all around me.
Drifting Snow in Minnesota can happen even in the cities of well plowed streets. One day driving in Austin , my car happen to drive 'up the snow-packed surface of a drift made by the strong winds blowing at my back. These winds 'Pack' the surface hard as the road itself and you are climbing the drift, unawares of the gradual climb. At the end of the drift, where the wind blown snow ceases to travel is where a rude awakening is to surprise you . this is where the Hard Pack has not yet happened and the snow is soft as powder and your car suddenly drops into this soft bed of snow. In my case, the car was now 4 feet higher then the road's surface! To the wind blow side, snow was as hard as a rock, to the downwind tail, soft as a bed of feathers.
My thoughts as to those 'Drifting Dunes' is that the same presses is happening.
A final note:
Since temps are So Extreme there, the same packing and windblown drifting is what we are seeing.