Rolling Stones in Kasei Valles
This scene shows the very steep side of a plateau, part of the northern limit of the Kasei Valles system, which is one of the largest outflow channel systems on Mars.
The difference in elevation here between the mostly flat channel's floor (bottom right) and the top of the plateau (top left) is over 1,300 m (0.8 miles), comparable in height to the Grand Canyon walls.
The Kasei Valles system is much wider than the Grand Canyon, though, getting to be in places 500 km (300 miles) wide. (The Grand Canyon's maximum width is 30 km, or 18 miles).
The image's subset (400 x 250 m or 440 x 270 yards; file size is 920 KB) shows numerous paths with the appearance of dotted lines, criss-crossing the steep side of the plateau. The carving agents can be found at the end of some of these paths: rocky blocks such as the ones in this subset, up to 2 m (2.2 yards) across (4 m or 4.4 yards across elsewhere in the image).
Some of these blocks traveled downhill several hundred meters (yards) as they rolled and bounced leaving behind a trail of indentations or poke marks in the surface's fine-grained, light-toned soils. The raised borders in some of these poke marks indicate they are relatively recent features, unaffected by wind erosion, or that this soil has cohesive properties, such as if it was cemented.
The sound of these blocks falling did not travel very far, though. According to computer simulations sound in Mars travels only 1.5% the distance it would travel on Earth. (No Martian sound has ever been recorded.) Hence, the same sound which would travel 1 km (0.6 miles) on Earth would travel only 15 m (16 yards) on Mars. This is due to the lower Martian atmospheric pressure, which is approximately 1% of that of Earth.
Image PSP_001640_2125 was taken by the High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter spacecraft on 02-Dec-2006. The complete image is centered at 32.2 degrees latitude, 306.0 degrees East longitude. The range to the target site was 292.4 km (182.8 miles). At this distance the image scale ranges from 29.3 cm/pixel (with 1 x 1 binning) to 58.5 cm/pixel (with 2 x 2 binning).
The image shown here has been map-projected to 25 cm/pixel and north is up. The image was taken at a local Mars time of 03:25 PM and the scene is illuminated from the west with a solar incidence angle of 50 degrees, thus the sun was about 40 degrees above the horizon. At a solar longitude of 144.1 degrees, the season on Mars is Northern Summer.