This is Hebes Chasm on Mars. It forms a giant trough nearly 4.97 miles (8 km) deep, of Valles Marinera, the largest canyon system in the solar system. Taken with the High Resolution Stereo Camera on Mars Express.
NASA’s Cassini spacecraft has spotted a river system stretching more than 200 miles on Saturn’s moon Titan. Though it isn’t the Nile — which is more than 20 times as long — the mighty river provides further evidence that this odd little moon is a wet world not unlike our own. Many lakes and small rivers have been found already on Titan but the newly discovered stream is the largest yet and represents the first time scientists have seen such a vast liquid system on any world other than Earth.