Click for full image.
Cool image time! The photo to the right, rotated, cropped and reduced to post here, was taken on May 13, 2021 by the high resolution camea on Mars Reconnaissance Orbiter (MRO). It spans the entire 4.7 mile width of the southern hemisphere canyon dubbed Reull Vallis. The white arrow indicates the direction of the downhill grade
The scientists title this image “Lineated Valley Fill.” The vagueness of this title is because they have not yet confirmed that this lineated valley fill is a glacier flowing downhill to the west.
Nonetheless, the material filling this valley has all the features one expects glaciers to exhibit. Not only is the the lineation aligned with the flow, it varies across the width of the canyon as glaciers normally do. At the edge the parallel grooves are depressed, probably because they are torn apart by the canyon walls as the glacier flows past. In turn, at the center of the flow the grooves are thinner and more tightly packed, and appear less disturbed. Here, the flow is smooth, less bothered by surrounding features.
This pattern also suggests the merging of two flows somewhere upstream.
A glance at the spectacular Concordia glacier in the Himalayas near the world’s second highest mountain, K2, illustrates the similarity of this Martian feature to Earth glaciers.
Reull Vallis itself flows down to Hellas Basin, the deepest basin on Mars. As it meanders downhill along its 650 mile length it steadily gets wider and less distinct as it drops into Hellas. Along its entire length MRO has photographed numerous similar examples of this lineated fill, all suggesting that under a thin layer of debris is a thick glacier, slowerly carving this canyon out.
The overview map below illustrates these facts nicely, while further reinforcing these glacial conclusions.
The small red rectangle in the center marks the location of today’s image. The two black crosses indicate earlier cool image posts (here and here), both of which exhibited similar glacial-like flow features.
In addition to the two other images mentioned above, I have highlighted many other glacial features in Reull Vallis. For example, an MRO image just to the west of this one and posted in October 2020 shows similar lineated features.
Do a search on Behind the Black for “Reull” and you will see plenty of cool images that say this canyon was carved by glaciers, not flowing water.
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