Exploratour - The Surface of Mars
Valles Marineris, the grand valley of Mars named after the Mariner program which first took close-up images.
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Image from: USGS
Click on image for full size
Image from: USGS
Valles Marineris
One of the most unusual places on Mars, shown in this image, is named Valles Marineris. Valles Marineris is not just one canyon, but a bunch of canyons.
The slopes of the canyons are very steep, and at the bottom are boulders and other debris. Scientists are still trying to figure out how the canyons were made.