The striking surface feature, called Aganippe Fossa, is a tectonic trench or graben – a long depression bounded on both sides by parallel normal faults. Astronomers first sighted it in 1930, but it was not officially named until 1976, according to the U.S. Geological Survey.
The graben is incomplete, with several interruptions in the “scar” from one end to the other, but it is considered a single structure stretching 600 kilometers. That is longer than the Grand Canyon of Colorado on Earth, which is 446 km from one end to the other.
However, the structure is significantly shorter than Mars’ Valles Marineris, the largest canyon in the solar system, which stretches for more than 4,000 km along the red planet’s equator.
The European Space Agency’s (ESA) Mars Express orbiter captured the newly released photos on December 13, 2023. One of the most interesting things in the images is the surrounding landscape, which varies on both sides of the giant rift.
“On the left (top in the image above), the terrain appears to be very uneven and contains several mounds, ruts and ridges. But on the right (bottom in the image above), the land looks smooth and is painted with zebra-like rocky streaks,” ESA representatives said.
This marked difference was probably caused by wind erosion to the right of the engraving, which over time weathered the surface of the planet in that area. Still, it is unclear why the rest of the surrounding landscape was unaffected.
Blame intense volcanic activity
Aganippe Fossa is located near the base of Arsia Mons, a 20-kilometer-high extinct volcano on the Tharsis plateau on Mars. This region is home to two other large volcanoes, Pavonis Mons and Ascraeus Mons, and together they form an almost perfect line perpendicular to the planet’s equator. This trio of peaks is flanked by Olympus Mons, the highest peak in the solar system, which lies just outside Tharsis and rises more than 25 kilometers (16 miles) above the surface, which is roughly three times the height of Mount Everest.
“It is likely that the scar was caused by a large magma plume that accumulated beneath Arsia Mons long ago, pushing up the planet’s crust and tearing the surface,” ESA representatives wrote.
It is currently uncertain how old Aganippe Fossa is, but NASA previously estimated that the volcano ceased to be active about 50 million years ago. However, scientists recently discovered evidence of a volcanic eruption on Mars dating back as recently as 50,000 years, suggesting that volcanic activity on our rubicund neighbor is not as old as previously thought.
Geologically interesting region
There are grabens similar to the one featured in this news item in Noctis Labyrinthus (meaning ‘Labyrinth of the Night’ in Latin), a huge canyon the size of Italy located between Tharsis and Valles Marineris.
The area surrounding Tharsis is one of the most geologically interesting regions on the red planet. This area also caught the attention of researchers earlier this year, following the discovery of a giant hidden volcano next to Noctis Labyrinthus and more than 150,000 tons of frozen water on the summits of the three Tharsis volcanoes.
