Click for original image.

Cool image time! The picture to the right, cropped, reduced, and enhanced to post here, was taken on May 5, 2026 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The science team labels this an “alluvial fan.” What we are looking at is the top 5,700 feet of a 9,400-foot-high cliff which is slumping downward. As it does so, its outer layers have been falling downward into the canyon below almost like liquid, producing the slope’s streaked look.

According to this definition, alluvial fans…

are mounds of coarse grained sediments formed when a confined stream disgorges into an unconfined area. They typically occur along the margins of mountain ranges where bedrock incised channels draining uplands spill out on to broad open valley floors. Alluvial fans occur in areas with significant topographic relief caused by rapid subsidence or uplift (rift basins, foreland basins, fold-and-thrust belts, etc.).

While the definition implies these fans only form from the flow of liquid water, that does not have to be the case. Many fans form from the long term downward motion of material from mountainsides into lower valleys or canyons, though water — either by rain, a freeze-thaw cycle, or streamflow — is usually a factor in causing this erosion.

At this location something has made that cliff slump, and in doing so produced the flow patterns on that slope

The white dot on the overview map to the right marks the location, on the north cliff of the 1,500-mile-long Kasei Valles, one of Mars’ longest channels thought to have been created by a catastrophic flood several billion years ago. During its history scientists believe a section of this canyon was temporarily filled with a lake, held in place by an ice dam. When that dam broke, it created a second catastrophic flood that further reshaped the canyon’s downstream portions. Subsequently part of the canyon floor was covered by a lava flow that traveled more than a thousand miles along the canyon in just a matter of weeks, almost like a tsunami on Earth.

The alluvial fill shown in the inset could very well have been caused to flow downhill during one of those catastrophic floods. Or maybe the lava flow disturbed it enough to activate it.

More likely, this fill has accumulated over eons at the base of the cliff. While this location is in the dry Martian tropics, the geology here suggests there may be ice impregnated deeper underground, aiding in this erosion.

Note however the deep fissures on the plateau above this cliff. That plateau is definitely slumping, with portions separating southward. At some point in the geological future an even bigger landslide should be expected.