Chasma

Chasma is a term used in astrogeology to refer to "a deep, elongated, steep-sided depression". The plural is chasmata. As of January 2013, the IAU had named 118 such features in the Solar System, on Venus (63), Mars (24), Saturn's satellites Mimas (6), Tethys (2), Dione (8) and Rhea (5), and Uranus's satellites Ariel (7), Titania (2) and Oberon (1). An example is Eos Chasma on Mars.