Almost everyone knows Olympus Mons, the largest volcano on Mars and also the largest in the solar system. But there are several other giant shield volcanoes on Mars. The second largest is Ascraeus Mons, and new images from ESA’s Mars Express spacecraft reveal some interesting features on the mountain’s side, or flank.
The images show regions where underground lava flows emptied from chambers or tubes and then collapsed into chains of craters. There are also smaller serpentine channels called “sinuous grooves” that meander in a sinuous path like a river. It’s commonly believed to be the remains of smaller collapsed lava tubes, but scientists are still unsure how they form. Collectively, these dramatic and large fissures on the lower southern flank of Ascraeus Mons – collectively referred to as Ascraeus Chasmata – cover a vast area over 70km across.
This perspective oblique or “side view” shows the southern flanks of Ascraeus Mons, the second tallest volcano on Mars. ESA/DLR/FU Berlin.
Ascraeus Mons is the northernmost and tallest of three prominent volcanoes in the Tharsis region of Mars, a volcanic plateau in the western hemisphere of Mars. Ascraeus Mons reaches a whopping 18 km (11.2 miles) in height, but its slopes are gentle, with an average gradient of 7 degrees. This slow rise is reflected in the volcano’s huge base diameter of 480 km, giving it an area roughly the size of Romania on Earth.
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Martian volcanoes in the Tharsis region. Credit: NASA/JPL
In comparison, Olympus Mons is 25 km (16 miles) high and 624 km (374 miles) in diameter (about the same size as the state of Arizona). On Earth, Mauna Kea in Hawaii has an elevation of 4,205 meters (13,796 feet); However, the base of the volcano is about 6,000 meters (19,685 feet) below sea level. So if you measure Mauna Kea from the base of the volcano on the ocean floor to the top, it is over 10,000 meters (33,000 feet) tall.
Mars Express has been orbiting the Red Planet since 2003, photographing the surface of Mars, mapping its minerals, identifying the composition and circulation of its thin atmosphere, while also probing the surface of its crust and studying how various phenomena in the Martian environment interact.
Further reading: ESA