Promethei Terra is a large Martian region, centered at 57.7°S 100°E and covering 3300 km at its broadest extent. It lies to the east of the massive Hellas basin. Like much of the southern part of the planet it is a heavily cratered, highland region. Promethei Terra was named for a classic albedo feature

Albedo feature

An albedo feature is a large area on the surface of a planet which shows a contrast in brightness or darkness with adjacent areas....

 of Mars, with the original name derived from that of the Greek god Prometheus

Prometheus

In Greek mythology, Prometheus is a Titan, the son of Iapetus and Themis, and brother to Atlas, Epimetheus and Menoetius. He was a champion of mankind, known for his wily intelligence, who stole fire from Zeus and gave it to mortals...

. Promethei Terra lies mostly in the Hellas quadrangle

Hellas quadrangle

The Hellas quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey Astrogeology Research Program. The Hellas quadrangle is also referred to as MC-28 ....

 of Mars.

Lobate Debris Aprons

One very important feature common in Promethei Terra are piles of material surrounding cliffs. These materials are called lobate debris apron

Lobate Debris Apron

Lobate debris aprons are geological features on Mars, first seen by the Viking Orbiters, consisting of piles of rock debris below cliffs. These features have a convex topography and a gentle slope from cliffs or escarpments, which suggest flow away from the steep source cliff...

s (LDA's). Recently, research with the Shallow Radar on the Mars Reconnaissance Orbiter

Mars Reconnaissance Orbiter

Mars Reconnaissance Orbiter is a NASA multipurpose spacecraft designed to conduct reconnaissance and Exploration of Mars from orbit...

 has provided strong evidence that the LDA's are glacier

Glacier

A glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation over many years, often centuries. At least 0.1 km² in area and 50 m thick, but often much larger, a glacier slowly deforms and flows due to stresses induced by its weight...

s that are covered with a thin layer of rocks. Large amounts of water ice are believed to be in the LDA's. Available evidence strongly suggests this area accumulated snow in the past. When the tilt (obliquity) of Mars increases the southern ice cap releases large amounts of water vapor. Climate models predict that when this occurs water vapor condenses and falls where LDAs are located. The tilt of the earth changes little because our relatively large moon keeps it stable. The two tiny Martian moons do not stabilize its planet, so the rotational axis of Mars undergoes large variations. Lobate debris aprons may be a major source of water for future Mars colonists. Their major advantage over other sources of Martian water are that they can easily mapped from orbit and they are closer to the equator where manned missions are more likely to land.