Tag: spaceflight

Today’s cool image will be unlike most cool images, in that we will begin not with the image but with the overview map to the right. The long meandering canyon at the center of this map is Nirgal Vallis, a 300-mile long canyon on Mars that eventually drains to the east into a much larger drainage system that runs south-to-north several thousand miles into the Martian northern lowland plains.

At first glance Nirgal Vallis invokes a river system. It starts in the west as several branches that combine to form a single major canyon meandering eastward until it enters that south-to-north system. To our Earth eyes, this canyon suggests it was carved by water flowing eastward, the many drainage routes combining as they flowed downhill.

Today’s the cool image, its location indicated by the white dot, tells us however that liquid water might not have been what created this canyon.
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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.
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