The High Resolution Stereo Camera (HRSC) aboard ESA’s Mars Express Orbiter imagined a fascinating landscape near the major Valles Marineris canyon system on the Red Planet.
Valles Marineris is a vast system of canyons that runs along the Martian equator 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 the Grand Canyon in Arizona.
It includes a myriad of cracks, channels, flows, fractures, and smaller signs of flow (like water, ice, lava, or debris).
Valles Marineris is a must-see scar on the face of Mars, and is believed to have formed when the planet’s crust was stretched by nearby volcanic activity, causing it to tear and crack before breaking down. collapse into the deep troughs we see today.
These troughs were shaped and eroded by water flows, landslides and other erosive processes, spacecraft, including Mars Express, spying on signs that water existed in parts of Valles Marineris in the relatively recent past.
The new HRSC instrument image from Mars Express shows “chaotic terrain” in Pyrrhae Regio – an area 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 to the left of the frame.
The bottom of the larger and higher basin stretches for about 40 km (25 miles) and contains fractures and marks that formed just after the crater itself.
Hot, molten rock is believed to have been thrown out during the crater-forming collision, after which it cooled and settled to form the scar-shaped features visible here.
Towards the middle of the frame, the surface is relatively smooth and featureless – however, two wide canals made their way through the landscape and can be seen as winding, branching indentations into the surrounding terrain.
The valleys are attached at their right end to the true star in the picture: a sunken, uneven, scarred patch of land called chaotic terrain.
Chaotic terrain, as the name suggests, looks jagged and muddled, and is believed to form as ice and subterranean sediment begin to melt and shift.
This changing layer causes the surface above to collapse – a collapse that can occur quickly and catastrophically as water flows rapidly through the Martian regolith.
Ice can be triggered to melt by heating events such as volcanic lava flows, sub-surface magmatism, impacts from large meteorites, or climate change.
In the chaotic terrain seen here, the ice melted, the resulting water drained away, and a number of disparate shattered blocks were left standing in the now empty cavities.
Remarkably, the soils of these cavities lie about 4 km (2.5 miles) below the flatter ground near the craters to the left.