Aganippe Fossa. Astronomers first spotted Aganippe Fossa on the surface of Mars as early as 1930, despite only naming it as such in the mid-1970s. A scar about 600 kilometers long and three to seven kilometers wide stretches across the flank of Arsia Mons, one of the planet’s largest volcanoes. And the European Space Agency’s (ESA) Mars Express mission, which has been in orbit around the Red Planet since 2003, has just sent back a striking new image of it.
How Was This Scar Formed?
Astronomers are unsure about the scar’s formation process. Some suggest that it originates from tectonics. It was formed by the Martian crust’s volcanic expansion. It could therefore be an isolated member of the Thaumasia Fossae, a group of grabens further south in the Tharsis region. Others suggest that the formation of volcanic “veins” in a late phase of Olympus Mons’ activity could also have led to the formation of giant dikes in the region. However, the morphology of Aganippe Fossa indicates that the collapse of lava tubes did indeed create these long depressions.
In the new image sent back by Mars Express’ High Resolution Stereo Camera (HRSC), researchers note a different landscape on each side of the scar:
— A so-called hummocky terrain, which includes numerous irregularly shaped mounds and valleys, all grouped together;
— And a smoother terrain, streaked with gently sloping cliffs and rocky debris.
Different Terrain on either Side of Aganippe Fossa
These terrains are characteristic of Arsia Mons’ “aureole.” A disk at the volcano’s base is linked to ancient glaciers. One aureole appears to have formed on the volcano’s northwest flank. Probably due to prevailing winds coming from opposite directions and controlling where ice was deposited over time. The zebra-like patterns likely also result from wind patterns that would have deposited darker materials than the ground there.