This is a shot from the High Resolution Stereo Camera (HRSC) aboard the European Space Agency's Mars Express Orbiter, showing Marineris Canyon, the largest and deepest canyon system known to man. But not aliens.
Stretching across the equatorial Martian highlands for some 2,485 miles (4,000 kilometers), Valles Marineris yawns 124 miles (200 kilometers) wide and up to 6.8 miles (11 kilometers) deep. Earth's 1.25-mile-deep (2-kilometer-deep) Grand Canyon could easily fit into one of Valles Marineris's smaller side valleys.
Wow, 6.8-miles -- that is DEEP. Granted nowhere near as deep as some of the philosophizing I do, but they don't call me a modern Plato for nothing. "Not Plato -- Play-Doh." Why, because I'm chubby?! You're going to give me a complex. PLUS A DOLLAR. "Why, so you can go buy more candy?" I already polished off my Halloween supply. :(
Thanks to my buddy c-nasty, who used the opportunity to made some reference to the canyon between the breasts of a girl he used to date when we were in college. Haha, you never dated that girl, bro.