Valles Marineris, the grand valley of Mars named after the Mariner program which first took close-up images.
Click on image for full size
Image from: USGS
Valles Marineris
Next to the Tharsis Ridge is Valles Marineris, a very long canyon of Mars.
As can be seen in the image, many huge ancient rivers extend toward the top of the image. The three Tharsis
volcanoes (dark red spots) are visible on the leftmost edge of the image. To the south are the highlands; very ancient ground, covered by many craters.
Better images returned by the Mars Global Surveyor spacecraft allow a closer look of this unusual canyon. These images show slopes descending steeply to the north and south
in broad,
debris-filled gullies. These gullies look a lot like canyons on Earth.
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