Behind The Black – Robert Zimmerman

For original images go here and here.

Today’s two cool images above provide a nice sense of the massive nature of many Martian landslides. Scientists often call this kind of slide “mass wasting,” because rather than it occurring because a single rock propagates a larger flow of rocks as it starts rolling downhill, this slide occurs because a large section of the hillside suddenly breaks free and moves downward as a unit, carving a path as it goes.

Mars has a lot of these kinds of slides, likely caused partly by its lower gravity, 39% that of Earth’s.

The overview map to the right marks the location of both slides by their numbers. Number one took place on the eastern interior rim of a 56-mile-wide and 7,000-foot-deep unnamed crater the dry tropics of Mars. The slide dropped about 3,000 feet, beginning about halfway down from the top of the rim and not quite reaching the crater floor. The picture was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on March 31, 2024.

Number two occurred on the western interior rim of a 32-mile-wide and 6,500-foot-deep unnamed crater in the mid-latitudes where near-surface ice and glacial features are often found. In this case the slide fell downward about 3,500 feet. The picture was taken by MRO’s high resolution camera on March 14, 2024.

Despite the different latitudes and thus different climates and geological settings, both landslides look similar. It is possible they occurred under similar conditions, but at very different times. Or it is also possible that the Mars gravity and general environment promotes these mass wasting events everywhere.

Click for original image.

Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on April 25, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The scientists label this layered deposits, but that hardly describes what we are looking at. This slope, as shown in the overview map above, is the north flank of the central ridgeline inside the giant enclosed canyon depression dubbed Hebes Chasma, located just north of the main canyon of Valles Marineris, the largest known canyon in the solar system.

From floor to peak the ridge is around 16,000 feet high. Yet, its peak sits more than 6,000 feet below the plateau that surrounds Hebes. In this one picture the drop from high to low is only 5,700 feet, with thousands of feet of cliff unseen below and above.

Yet every single foot of these gigantic cliffs is layered. Based on close-up data obtained by Curiosity on the slopes of Mount Sharp in Gale Crater on the other side of the planet, the layers we can see here only represent the most coarse sedimentary boundaries. Within these layers are likely thousands upon thousands of thin additional layers, each likely representing some cyclical climate proces on Mars, even down to individual years.

Note too that the lower slopes in this picture (near the top) suggest some form of erosion flowing downhill. What caused that erosion process however remains unknown. It could have been liquid water, or glaciers, or some other process unique to Mars that we still haven’t uncovered.