Click for original image.

Cool image time! The picture to the right, cropped and reduced to post here, was taken on May 28, 2026 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The scientists label this a “small slump landslide,” though it really isn’t that small. From rim to floor that cliff drops more than 3,700 feet. The landslide itself appears to have dropped about 2,300 feet, with the debris pile at the base a mile wide and about three-quarters of a mile long. The force of the collapse pushed that debris a half mile into the crater.

What caused the collapse? Maybe an impact on the rim (such as that 1,900-foot-wide crater near the top of the image) caused this section to break off as a unit. Or possibly a seasonal freeze/thaw cycle of ice or dry ice weakened the cliff face, allowing this large section to separate. Or maybe there was once ice impregnated in the ground and the cliff simply became structurally weak and collapsed.

The location, as shown on the overview map below, tells us however that if either of the last two theories is correct, neither could not have happened recently.

The white rectangle on the overview map to the right marks the location, in the dry equatorial regions of Mars where presently no near surface ice is found. Thus, if a freeze-thaw cycle or impregnated underground ice caused this collapse, it would have had to happened a long time ago (one or more billion years), when the Martian equatorial regions had ice or water.

And this location, at the outlet for Mars’ largest canyon, Valles Marineris, almost certainly once had ice or water present, in large amounts. Data from both the Viking-1 and Pathfinder landers to the north and down stream from this location suggest that large catastrophic floods once poured out from Valles Marineris and filled this region with large intermittent bodies of water, as shown on the map. This standing water did not last long, but all data suggests it was there. It is also possible it was ice for long periods, moving like glaciers across the surface.

Tana Vallis, the 27-mile-long drainage canyon in which this landslide exists, has the U-shaped cross-section of a canyon carved by a glacier, and Galilaei Crater, 85-miles wide and about 1.5 miles deep, could easily have been filled with ice from which this glacier flowed. Or just as likely, the water/ice from that inland sea could have flowed into Galilaei.

Even so, the landslide likely occurred shortly after that glacier had sublimated away. The disappearance would have removed the structural support of the glacier that held the cliff up. Once gone there was nothing to keep this mass of material from falling.