Valles Marineris greatest Canyon in our Solar System (or Mariner Valley), is 4000 km (2500 mi) long and reaches depths of up to 7 km (4 mi)! Image credit: ESA/DLR/FU Berlin (G. Neukum)
During its examination of Mars, the Viking 1 spacecraft returned images of Valles Marineris, a huge canyon system 5,000 km, or about 3,106 miles, long, whose connected chasma or valleys may have formed from a combination of erosional collapse and structural activity. This synthetic oblique view shows Ophir Chasma, the northern most one of the connected valleys of Valles Marineris.
This is the largest canyon in the Solar System and cuts a wide swath across the face of Mars. Named Valles Marineris, the grand valley extends over 3,000 kilometers long, spans as much as 600 kilometers across, and delves as much as 8 kilometers deep.