Serpent Scar on Mars

This scar, known as the Aganippe Fossa, is an uneven, roughly 600 km long feature known as a “graben”: a trench-like trench with steep walls on either side.

Aganippe Fossa intersects the lower flank of one of the largest Martian volcanoes, Arsia Mons. Mars Express regularly observes Arsia Mons and its close companions in the Tharsis region, home to several monstrous volcanoes on Mars. This includes Olympus Mons, the tallest volcano in the Solar System (visible on the context map associated with this new image, as is Arsia Mons).

Arsia Mons itself measures 435 km in diameter and rises more than 9 km above the surrounding plains. For context, the highest dormant volcano on Earth, Ojos del Salado on the Argentina-Chile border, has a summit below 7 km.

Leaking lava

We’re still not sure how or when Aganippe Fossa formed, but it seems likely that it formed when magma rising beneath the colossal mass of Tharsis volcanoes caused the Martian crust to stretch and crack.

In this view, Mars Express’s High Resolution Stereo Camera (HRSC) captures two different types of terrain: so-called bumpy terrain, which consists of many irregularly shaped hills and valleys all grouped together, and lobed terrain, which is made up of gently sloping cliffs and rocky debris.

These terrains are characteristic of the ringed “halo” of Arsia Mons, a 100,000 square kilometer disk around the base of the volcano, probably associated with ancient glaciers. Interestingly, this halo only formed on the northwest flank of the volcano, likely due to prevailing winds from the opposite direction controlling where the ice settled over time.

Windblown dust and sand have also shaped this part of Mars, creating interesting zebra patterns to the right of the frame as darker material is deposited on lighter ground (or vice versa!). The surface here also shows evidence of lava flows from when the volcano was active.

Mars exploration

Mars Express has been orbiting the Red Planet since 2003. It scans the surface of Mars, maps its minerals, identifies the composition and circulation of its tenuous atmosphere, probes beneath its crust, and studies how various phenomena interact in the Martian environment.

The HRSC probe responsible for these images has revealed much about the diverse surface of Mars over the past 20 years. His images show everything from wind-sculpted ridges and ridges to sinkholes on the flanks of colossal volcanoes to impact craters, tectonic faults, river channels and ancient lava lakes. The mission has been extremely productive throughout its existence, creating a much fuller and more accurate understanding of our planetary neighbor than ever before.

The Mars Express High Resolution Stereo Camera (HRSC) was developed and operated by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR).