Behind The Black – Robert Zimmerman

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Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on May 31, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

I think the many parallel ridges are likely hardened and petrified dunes of sand because of their craggy nature. Dunes of sand would have a smoother, softer look, and in fact, if you look at some of the dunes inside the depression at the bottom-right of the picture you will see ridges with exactly that look, smooth and curved.

Nor is it unreasonable to believe these ridges are petrified dunes, as orbital data over time has found that many of the dunes on Mars, even those that look active, are not and have likely been hardened for centuries.

As for the ridges running at right angles to each other in the picture’s middle left, I have no idea. Possible we are looking at ancient dykes of lava that pushed up through cracks and faults, but this is pure guess.
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Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on April 12, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the scientists simply label as “Northern Mid-latitude Terrain”.

I have focused in on that meandering channel and the landscape around it. On Earth we would assume that channel marks the drainage of a river or stream, possibly also shaped by a glacier at some point because of its U-shaped profile. This guess is strengthened by the elevation data from MRO, which shows the channel descending to the southwest about 440 feet along its 2.2 mile length.

The channel and the eroded look of the surrounding terrain suggests strongly the presence of near-surface ice at this location, which is not unreasonable based on its 32 degree north latitude. The wider look below only adds further strength to this hypothesis, but also adds a lot more details explaining the genesis of this strange landscape.
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Today’s cool image could be labeled a “What the heck?!” photo, as the origin of its most distinct feature is utterly baffling. The picture to the right, cropped, reduced, and sharpened to post here, was taken on June 18, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), and shows what look like a collection of meandering ridges peeking out from a terrain covered by thick dust.

The scientists label this dust-covered ground, as well as the ripple dunes to the south in the full image, “sand sheets.” Without question, the ground here seems to resemble a Sahara-like terrain. It is utterly featureless, other than the few bedrock features that poke up out of that sand. In the full image some peaks stick out, but it the meandering ridges in this section that are most intriguing. They are reminiscent of rimstone dams in caves, but what formed them remains baffling, since cave rimstone dams are formed by the interaction of limestone and water, and there is absolutely no evidence of any near surface ice at this location in the dry equatorial regions of Mars.

All the ridges signify is a buried terrain formed in some inexplicable way.
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Today’s cool image is actual one new picture and four past images, which taken together reveal something about the larger wind patterns on Mars. The picture to the right, cropped, reduced, and sharpened to post here, was taken on June 27, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO) and shows a tiny wind-swept section of the giant volcanic ash field dubbed the Medusae Fossae Formation, about the size of the subcontinent of India and thought to be source of most of the dust on Mars.

The innumerable parallel thin ridges here all suggest that the prevailing winds blow from the southeast to the northwest. As they blow, the scour the surface ash out, and sometimes reveal the underlying bedrock, which here shows up as those small peaks and a handful of northeast-to-southwest trending larger ridges. Note too that the picture shown is only a small section of the full image, which shows that this landscape continues for a considerable distance in all directions.
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