Mars is clearly much smaller than Earth, but it can still come up with impressive superlatives, particularly spectacular is the Valles Marineris canyon system. This graben, up to 11 kilometres deep and 200 kilometres wide, stretches almost 4000 kilometres across the Martian highlands in an east-west direction along the equator. The Grand Canyon in the United States (almost two kilometres deep) would easily fit into one of the smaller valleys that run parallel to Valles Marineris.
Copyright note:
As a joint undertaking by DLR, ESA and FU Berlin, the Mars Express HRSC images are published under a Creative Commons licence since December 2014: ESA/DLR/FU Berlin, CC BY-SA 3.0 IGO. This licence will also apply to all HRSC images released to date.