The high-resolution stereo camera (HRSC) aboard ESA’s Mars Express orbiter has captured a fascinating landscape near the great canyon system of Valles Marineris on the Red Planet.
This image from the High Resolution Stereo Camera (HRSC) on board ESA’s Mars Express shows craters, valleys and chaotic terrain in Pyrrhae Region, Mars. Chaotic terrain forms as a shifting underground layer of melting ice and sediment, causing the surface above it to collapse. In the chaotic terrain seen here, ice has melted, the resulting water has drained, and a number of disparate broken blocks have been left in now-empty cavities (which once contained ice). This image contains data collected by HRSC on August 3, 2020. Image credit: ESA / DLR / FU Berlin / CC BY-SA 3.0 IGO.
Valles Marineris is a huge canyon system that runs along the equator of Mars, just east of the Tharsis region.
It is 4,000 km (2,500 miles) long and reaches depths of up to 7 km (4 miles) – about 10 times longer and 5 times deeper than Arizona’s Grand Canyon.
It includes numerous smaller crevices, channels, outflows, fractures and signs of flowing material (such as water, ice, lava, or debris).
Valles Marineris is an indispensable scar on the surface of Mars, believed to be formed when the planet’s crust was stretched by nearby volcanic activity, causing it to rupture and burst open before collapsing into the deep troughs we see today.
These troughs have been further formed and eroded by water currents, landslides and other erosive processes, with spacecraft, including the Mars Express, spying on signs that water existed in parts of Valles Marineris in the relatively recent past.
Perspective of chaotic terrain in Pyrrhae Region, Mars. Image credit: ESA / DLR / FU Berlin / CC BY-SA 3.0 IGO.
The new image from Mars Express’s HRSC instrument shows “chaotic terrain” in Pyrrhae Regio – a region south of Eos Chasma, an eastern branch of the Valles Marineris system.
A scattering of impact craters, formed when incoming bodies from space collided with the surface of Mars, can be seen on the left side of the frame.
The bottom of the largest and upper basin covers approximately 40 km (25 miles) and contains some fractures and markings that formed just after the crater itself.
Hot, molten rock is said to have been thrown up during the crater-forming impact, then cooled and settled to form the scar-like features visible here.
Towards the center of the frame, the surface is relatively smooth and characterless – but two wide channels have cut their way through the landscape and can be seen as meandering, branching notches in the surrounding terrain.
The valleys are attached on their right to the real star of the image: a sunken, uneven, scarred patch of ground known as chaotic terrain.
Chaotic terrain, as the name suggests, looks irregular and jumbled and is thought to form as the ice and sediment below the surface begin to melt and shift.
This shifting layer causes the surface above it to collapse – a collapse that can happen quickly and catastrophically if water drains rapidly through the Martian regolith.
Ice can be triggered to melt by heating events such as volcanic lava flows, underground magmatism, impacts from large meteorites, or changes in climate.
In the chaotic terrain you see here, the ice has melted, the resulting water has drained, and a number of different broken blocks have been left in now-empty voids.
It is noteworthy that the floors of these cavities are about 4 km below the flatter ground near the craters on the left.