This picture was stitched together from over 100 images taken by the Viking Orbiters back in the ’70s. It shows the largest canyon in the Solar System cutting a wide swath across the face of Mars. Valles Marineris is over 3,000 km long, is as much as 600 km across, and is as much as 8 km deep. The Earth’s Grand Canyon is 800 km long, 30 km wide, and not quite 2 km deep. The origin of the Valles Marineris remains a mystery, although a leading hypothesis holds that it started as a crack billions of years ago as the planet cooled.
Image Credit: USGS / NASA