Click for full image.

Cool image time! The photo to the left, rotated, cropped, and reduced to post here, was taken on June 1, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows the rim edge to a fifteen-mile-wide canyon, with many apparent layers exposed on the high plateau.

The layers are intriguing in that they suggest several things. First, they give us a glimpse into the top and youngest layers that make up the interior canyon wall. Second, they tell us that erosion has removed much of those top and youngest layers, resulting in the mesas on that plateau.

Finally, the gullies flowing down into the canyon indicate further erosion processes, eating away at the canyon wall over time.

The location of this canyon is also intriguing.

The small white rectangle in the southern part of Argyre Basin marks the location of this canyon. It is a strange teardrop-shaped canyon, suggesting some form of flow from the south to the north that washed away part of the basin’s floor.

Argyre Basin is the second largest basin on Mars, about 1,100 miles in diameter with its lowest elevation 17,000 feet below the surrounding southern cratered highlands. It is believed to have been formed by a giant impact billions of years ago. Since that impact this particular canyon formed, and it appears to have formed by some underground drainage flowing down from the mountains to the south. Since the basin sits entirely within the 30 to 60 degree mid-latitude band where many glaciers are found on Mars, assuming a glacier was a factor in forming this canyon is entirely reasonable, though obviously unproven at this time.

That there does not appear to be any obvious glacial material at this location in the full MRO image illustrates the uncertainty of this assumption. Yet, glaciers are found in this region. If they are not here now, they could likely have been here in the past, and thus might explain the canyon’s formation and later erosion processes.

The canyon’s shape also suggests the possibility that it formed by flowing water. It surely looks like the kinds of resurgences one sees in limestone karst regions on Earth, where underground rivers reach the surface as springs, and then subsequently flow on the surface, carving out canyons.

There is no water here now, however, either as liquid or ice. Figuring out the layers and formation of this canyon cannot be easily understood until someone can walk along its walls and take rock samples, in great numbers.