A large impact crater on a planet or moon, typically several hundred kilometers across, flooded with basaltic lava and surrounded by concentric rings of faulted cliffs.
From O.Fr. bacin, from V.L. *baccinum, from L. bacca "water vessel," perhaps originally Gaulish.
Howzé, from howz "pond, a large reservoir of water" (from Ar. hauz) + -é noun suffix.
Fr.: bassin de Hallas
One of the largest identified → impact craters both on → Mars and within the → Solar System. Hellas spans more than 2000 km across in the → southern hemisphere, a region that is much more heavily cratered and higher in average elevation than the northern hemisphere. The depth of Hellas from its bottom to its inner rim is more than 4 km. In comparison, the depth of the Grand Canyon in the United States is roughly 1.6 km, that is 2.5 times smaller! The western part of the Hellas basin contains the lowest point on Mars, about 8.2 km below the Mars datum or Martian "sea level." The formation of the impact structure is believed to have taken place in the early Noachian epoch, between 3.9 and 4.6 billion years ago (Planetary Science Institute webpage).
Hellas refers to the classical name for Greece; → basin.