Behind The Black – Robert Zimmerman

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Today’s cool image illustrates the complex explanations scientists sometimes have to come up with explain the strange geology seen on Mars. The picture to the right, cropped, reduced, and sharpened to post here, was taken on May 30, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the scientists label as a whitish “ridged flow-like feature” that appears to exit out of the massive hill to the west.

The white dot on the overview map above as well as in the inset marks this location, smack dab inside the 2,000-mile-long strip of glacier country in the Martian northern mid-latitudes. As you can see from the inset, that massive hill is actual the foot of a large apron of material, likely ice-infused, that has sagged down from the large 5,400-foot high mesa to the west.

The white material is likely what the scientists call an inverted river. Once it was a channel in which either water or ice flowed. With time the weight of that material compacted the riverbed so that it was denser than the surrounding terrain, much of which was likely soft anyway because of a high ice content. When that surrounding terrain eroded away, the riverbed resisted that erosion, and instead became the raised ridge we now see.

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Cool image time! The picture to the right, rotated, cropped, and sharpened to post here, was taken on May 14, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a small section of a vast dune field, 50 miles square, that sits about 225 miles south of the southern foothills of Mars’ biggest volcano, Olympus Mons.

The dunes are probably less than 20 feet high, with that one small hill only slightly higher. Their similar orientation, which extends across the entire 50-mile-square dune field, indicates the direction of the prevailing winds, which I think (but will not swear to it) is from the southeast to the northwest, which also happens to also follow the grade downhill to the northwest.

It is also possible that wind direction is the reverse, and goes uphill to the southwest.
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Click for original image.

It is time for two cool images! The picture to the right, cropped, reduced, and sharpened to post here, was taken on May 10, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), and is one of two glaciers imaged by MRO in May that are among a whole series of glaciers flowing down the south wall of the same mesa.

The red dot in the inset and on the overview map above marks the location of the picture to the right. The white dot marks the location of the May 27, 2023 picture, which can be seen here.

The unnamed 10,000-foot-high mesa from which these glaciers flow, located in the middle of the 2,000-mile-long northern mid-latitude strip I dub glacier glacier country, is about 41 miles long and 18 miles wide at its widest point. The glacier to the right falls about 6,000 feet in about four miles, making the grade steep, ranging from 15 to 23 degrees. That steepness explains the split in the glacier, as it flowed around a huge piece of higher bedrock in the middle of this descending hollow.

Both images provide further evidence of the dominance of glaciers in this mid-latitude region. While the glaciers are all covered with dust and debris to protect the ice, and are also thought at present to all be inactive, they also all suggest a very dynamic Martian geological and climate history, one that will likely come alive again as the planet’s rotational tilt naturally shifts back and forth from its present 25 degree tilt to 11 to 60 degrees.

The glaciers also show us again that Mars is not a dry desert, but above 30 degrees latitude it is an icy desert much like Antarctica. Colonists will have no trouble finding water.