Ascraeus Mons /əˈskriːəs ˈmɒnz/ is a large shield volcano located in the Tharsis region of the planet Mars.

As the dust cleared, the spots were revealed to be extremely tall volcanoes whose summits had projected above the dust-laden, lower atmosphere.

[5] Slopes are steepest in the middle portion of the flanks, flattening out toward the base and near the top where a broad summit plateau and caldera (collapse crater) complex are located.

[5][8] Like most of the Tharsis region, Ascraeus Mons has a high albedo (reflectivity) and low thermal inertia, indicating that the volcano and surrounding areas are covered with large amounts of fine dust.

Ascraeus Mons is surrounded by lava flow plains that are mid to late Amazonian in age.

The lava plains northwest of Ascraeus Mons are notable for having two dark collapse pits photographed by the HiRISE camera on the Mars Reconnaissance Orbiter (MRO) in November 2010 (pictured in gallery below).

[14] These rimless pit craters are believed to form by collapse of surface material into a subsurface void created either by a dike or lava tube.

[23] The flanks of Ascraeus Mons have a rumpled appearance caused by numerous low, rounded terrace-like structures arranged concentrically around the summit of the volcano.

Individual terraces are not continuous around the volcano, but instead consist of arcuate segments that overlap with each other, forming an imbricate pattern.

[25] They are interpreted to be the surface expression of thrust faults that formed due to compression along the volcano's flanks.

[26] Fissures, or flank vents, at the southwestern and northeastern edges of the volcano are the sources of the lava aprons that spread out across the surrounding plains.

Whether the channels were formed predominately by water or lava is still a topic of debate,[28] though extensive study of analogous environments (e.g. Hawaii, the Moon, elsewhere on Mars) and morphologic features by multiple researchers has led to the conclusion that a volcanic origin is most probable.

[31] A small, partly preserved depression southeast of the main caldera may be as old as 3.8 billion years (Gyr).

The FSD at Ascraeus Mons is the smallest of those on the Tharsis Montes, covering an area of 14,000 km2 and extending outward from the volcano's base for about 100 km.

[33] During periods of high obliquity (axial tilt) the polar regions receive higher levels of sunlight.