Late Heavy Bombardment
The Hellas quadrangle contains part of the Hellas Basin, the largest known impact crater on the surface of Mars and the second largest in the Solar System. The depth of the crater is 7152 m (23,000 ft) below the standard topographic datum of Mars. The basin is located in the southern highlands of Mars and is thought to have been formed about 3.9 billion years ago, during the Late Heavy Bombardment.