Click for original image.

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on August 31, 2025 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The science team labels this as “layering”, which surely is an apt description. As the latitude is 9 degrees south, this location is within the dry tropics of Mars, where no near surface ice has yet been found. Thus, the terraced layers of this low 20-foot-high mesa are not indicative of the many glacial climate cycles found in the mid-latitudes.

Instead, we are looking at sedimentary layers of rock or dust, laid down over time and later exposed by erosion.

So what caused the layers? And what is causing them to be exposed, one by one? As always the overview map helps provide a possible explanation.

The white dot near the center of the overview map to the right marks the location, several hundred miles north of where the rover Spirit landed and inside the Medusa Fossae Formation, the largest volcanic ash deposit on Mars (about the size of India) and believed to be the source of much of the red planet’s dust.

The layers thus likely represent different volcanic eruptions over time, each laying down a new deposit of volcanic ash. Since the major volcanoes of Mars have been largely inactive now for about a billion years, there has been ample time since for the thin wind of Mars to slowly peel away this ash, revealing this terraced butte.

That’s my off-the-cuff theory, strengthened by other images in this region showing similar layering.

It is also possible however that these layers are not ash, but frozen lava, also laid down by multiple eruptions. The Medusae Fossae Formation is patchy in this region, so we might be looking at old lava, not ash deposits.