Hellas Planitia is a plain located within the huge, roughly circular impact basin Hellas located in the southern hemisphere of the planet Mars. Hellas is the third or fourth largest impact crater and the largest visible impact crater known in the Solar System. The basin floor is about 7,152 m (23,465 ft) deep, 3,000 m (9,800 ft) deeper than the Moon's South Pole-Aitken basin, and extends about 2,300 km (1,400 mi) east to west. It is centered at 42°24′S 70°30′E / 42.4°S 70.5°E / -42.4; 70.5. Hellas Planitia is in the Hellas quadrangle and the Noachis quadrangle.

Description

With a diameter of about 2,300 km (1,400 mi), it is the largest unambiguous impact structure on the planet, the obscured Utopia Planitia is slightly larger. Though it's distant second and third for both if the Borealis Basin proves to be an impact crater. Hellas Planitia is thought to have been formed during the Late Heavy Bombardment period of the Solar System, approximately 4.1 to 3.8 billion years ago, when a large asteroid hit the surface.