Ascraeus Mons is the northernmost and tallest of three prominent volcanoes found in the Tharsis region of Mars, a volcanic plateau in the planet’s western hemisphere.
This image from ESA’s Mars Express shows the southern flanks of Ascraeus Mons, the second-tallest volcano on Mars. This image comprises data gathered by Mars Express’ High Resolution Stereo Camera (HRSC) on January 15, 2023. Image credit: ESA / DLR / FU Berlin / CC BY-SA 3.0 IGO.
Ascraeus Mons was first discovered by NASA’s Mariner 9 spacecraft in 1971.
This volcano was originally called North Spot because it was the northernmost of only four spots visible on the Martian surface due to a global dust storm.
Ascraeus Mons measures a towering 18 km in height but its slopes are gentle. This slow climb is reflected in the volcano’s huge base diameter of 480 km.
The volcano is surpassed in height only by Olympus Mons, the tallest volcano not only on Mars but in the entire Solar System.
“Ascraeus Mons is no longer active today,” said members of the Mars Express team.
“It has a very flat profile with an average slope of only 7 degrees.”
The new images from the High Resolution Stereo Camera (HRSC) on board Mars Express, show part of the southern flank of Ascraeus Mons.
“The difference in altitude between the south and the north (top) of the image is approximately 10 km,” the researchers said.
“On Earth, such differences in altitude are found only on the 4-km-high shield volcanoes of the Hawaiian Islands, which rise out of the 5.5-km-deep Pacific Ocean.”
“The unusual terrain shown here is called Ascraeus Chasmata — a huge area more than 70 km in extent on the lower southern flank of the volcano, characterized by collapsed former lava channels.”
To the north of the frame lie numerous wrinkled lava flows.
“This crinkled ground then encounters chains of ‘pit craters:’ features where strings of circular or near-circular depressions have combined and coalesced to form troughs,” the scientists said.
“We see these on Earth too, with a notable example being the dramatic Cenotes found on the Yucatán Peninsula, Mexico.”
“The pit crater troughs and chains shown here have also grouped together to form an especially large and eye-catching collapse area.”
“These chains and troughs likely form where hidden voids lie below the surface, causing ground to become unstable and collapse — a bit like a sinkhole.”
“The subsurface voids are thought to be created as the surface layer of a lava flow rapidly cools and hardens.”
“The lava flow beneath then ceases and ebbs away over time, leaving tube-shaped pockets of space lurking several meters below ground.”
“The ground below the pit crater chains is marked by so-called ‘sinuous rilles:’ smaller, snaking channels without rims that are often found at the flanks of volcanoes.”
“It is still unclear how these form, but their creation may involve flows of lava, ash or water — or a combination of the three.”
The lowest part of the image is dominated by large fissures of up to 40 km long.
“Branching out from these fissures are channels that weave and braid together (braided channels), isolating chunks of Martian terrain to form ‘islands’ and terraces,” they said.
“These are likely to have formed by water — perhaps as snow and ice built up on the flanks of Ascraeus Mons before later melting away.”
