A satellite orbiting Mars has captured the best-ever images of a giant “scar” carved into the Red Planet’s surface. The dark ravine, which is accompanied by unusual zebra-like stripes, is likely the result of extreme volcanic activity millions of years ago.
The striking surface feature, called the Aganippe Fossa, is a graben—”a ditch-like groove with steep walls on either side,” according to European Space Agency (ESA). Astronomers first spotted it as early as 1930, but it wasn’t officially named until 1976, according to US Geological Survey.
The graben is incomplete, with various breaks in the groove from end to end, but is considered a single structure that extends for about 375 miles (600 kilometers). That’s longer than the Grand Canyon, which is 277 miles (446 km) from end to end, according to National Park Service. However, the structure is still significantly shorter than that of Mars Valles Marineris — the largest canyon in the Solar System, stretching more than 2,500 miles (4,000 km) along the Red Planet’s equator.
ESA’s Mars Express orbiter captured the newly released images on December 13, 2023. The satellite has been circling the Red Planet in an elliptical orbit for more than two decades.
One of the most interesting things about the photo is the surrounding landscape that varies on either side of the giant fissure. To the left the ground appears very uneven and contains several mounds, hollows and ridges. But to the right, the ground appears smooth and is painted with “zebra-like” rocky stripes, ESA officials said.
This stark difference was likely caused by historical wind erosion to the right of the graben that wore away the planet’s surface in that area. However, it is not clear why the rest of the surrounding landscape is not affected.
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Aganippe Fossa is located near the base of Arsia Mons, a 12-mile (20 km) high extinct volcano on Mars’ Tharsis Plateau. This region contains two other large volcanoes, Pavonis Mons and Ascraeus Mons, and together the three dead peaks form an almost perfect line perpendicular to the planet’s equator. The trio is flanked by Olympus Mons, the the highest peak in the solar systemwhich lies just outside Tharsis and stands more than 16 miles (25 km) above the surface – about three times the height of Mount Everest.
The scar is likely caused by a large cloud of magma that gathered beneath Arsia Mons a long time ago, pushing the planet’s crust up and ripping the surface, ESA officials wrote.
It is currently unclear how old Aganipe Fossa is, but NASA pre-assessed that the volcano stopped erupting about 50 million years ago. However, scientists have recently found evidence of a Volcanic eruption on Mars only 50,000 years agohinting that volcanic activity on the Red Planet is not as ancient as we previously thought.
Similar grabens also exist in Noctis Labyrinthus (meaning “Labyrinth of the night‘ in Latin) is a massive canyon the size of Italy that lies between Tharsis and Valles Marineris.
The area around Tharsis is one of the most geologically interesting regions of the Red Planet. The region also caught the attention of researchers earlier this year after the discovery of a a giant volcano hidden next to Noctis’ Labyrinth and more than 150,000 tons of frozen water through the peaks of the three volcanoes of Tharsis.
