Behind The Black – Robert Zimmerman

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on October 2, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The white dot in the overview map above marks the location, inside the chaos terrain of Deuternilus Mensae and part of the 2,000-mile-long mid-latitude Martian strip I label “glacier country,” because practically every image of every part of its landscape has glacial features. For example, the splash apron around the picture’s largest crater as well as the material within it all suggest some form of glacial activity and near-surface ice.

The scientists label what they see here as “Mesas in Small Craters.” These features are located in a low flat plain that geologists think was created when the ground eroded away, leaving behind scattered high plateaus that indicate the previous surface elevation. The geological map [pdf] of this plain describes it as follows:

Smooth, relatively featureless materials with regions of variable albedo north of continuous cratered highlands; exhibits scattered clusters of small circular to irregular knobs.

Based on the many accumulated photos from MRO, the general conclusion is that we are looking at a sheet of ice/dirt and covered by a thin dust layer that acts to protect that ice from sublimating away. When wind blows that dust off and the summer sun hits that near-surface ice, however, it does sublimate in bursts, which thus provides an explanation for the erosion that caused these low featureless plains.

As for these strange terraced mesas inside these distorted hollows, my guess is that the mesas predate the icesheet and are made of material with less ice impregnated within it. As that ice sublimates away it creates the craters within which the mesas remain. The terraces suggest a earlier series of geological sedimentary history.

Click for original image.

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on September 27, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The picture was simply labeled a “terrain sample,” which usually means it was taken not as part of any specific research request, but to fill a gap in the schedule so as to maintain the camera’s proper temperature. When such gap-filler pictures are necessary, the MRO camera team tries to snap something of interest. Sometimes the pictures end up somewhat boring. This time however the picture highlights a dune field that is unusually light in color.

Since most Martian sand is volcanic in origin, it tends to look dark in orbital pictures. That this sand looks bright could be because it is inherently different, or it could be that lighting conditions make what normally looks dark to look bright instead.
» Read more

Click for original image.

Today’s cool image is another example of what I call a “What the heck!” image. The picture to the right, simply cropped to post here, was taken on September 22, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

It shows what the scientists label as “etched terrain,” an incredibly twisted and eroded landscape that to me actually defies description. In trying to research what scientists have learned and theorized about this terrain, it appears they think it is material that flowed over older terrain (thus its lack of many craters) that was subsequently eroded by later processes.

Why it eroded so strangely however is not really understood. It could have been caused by near-surface ice sublimated to the surface and thus causing many breaks, but since this terrain is located right on the equator in the dry tropics, it is a very long time since water was present here.
» Read more

Click for original image.

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on July 9, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The white dot on the overview map above marks the location, inside the deep enclosed and very large 130-mile-wide depression dubbed Juventae Chasma.

The mountain in the picture raises above the sand sea that surrounds it from 1,000 to 2,300 feet, depending on direction, as the downhill grade of the sand sea is to the east. Thus, on the west the mountain rises less, while on the east the height is the greatest.

The inset illustrates the extent of the sand sea. It covers the ground for many miles in all directions. The way the sand surrounds these mountains suggests the prevailing winds blow from the west to the east. In fact, the facts suggest that this sand is volcanic ash that was blown into Juventae from many eruptions that occurred over time to the west, where it got trapped. The wind and gravity deposited the sand into the 20,000 to 25,000-foot-deep chasm, where the wind was insufficient to lift it out again.

One wonders how deep that sand sea might be. The lack of any surface features at all suggests it could be quite deep, burying everything but the highest peaks. In fact, if a geologist could drill a core through that sand I suspect he or she might be able to document the entire eruption history of much of Mars.