ESA’s Mars Express has returned to its primary mission of studying the geology and atmosphere of Mars from orbit, after providing support to the Curiosity rover.
This image was created combining High-Resolution Stereo Camera (HRSC) nadir and colour channel data taken by Mars Express. The spacecraft imaged the 120 km wide Hadley Crater during revolution 10572 on 9 April 2012. The image has a ground resolution of about 19 m per pixel, and is centred at around 19°S and 157°E. The crater lays to the west of the Al-Qahira Vallis; it is in the transition zone between the old southern highlands and the younger northern lowlands.
The image shows the main 120 km wide crater, with multiple impacts at later epochs within it. The impacts reached depths of up to 2,600 m below the surrounding surface. These impacts were from large asteroids and/or comets and occurred early in the crater’s formation after infilling with lava and sediments. There is evidence that some of these later impacts were partly buried as there are wrinkle ridges to the north of the crater floor and hints of more crater rims to the west.
There is also evidence of mass wasting, which is where surface material moves down a slope due to gravity. This evidence presents as the southern left side of the crater appearing shallower than the opposite side. It is hard to determine what caused this mass wasting or when it occurred; it can be started by earthquakes (Marsquakes), ice splitting the rocks through a process called freeze-thaw, or water being introduced into the slope material.
The ejecta of the smaller craters within Hadley are particularly interesting. There is evidence for volatiles within two of them, which suggests possible water ice beneath the surface. Upon impact, the ice would mix with surrounding materials to form a kind of ‘mud’ which is then ejected over the surface. The ice could be present to a depth of hundreds of metres.
Hadley crater is named after British lawyer and meteorologist George Hadley (1685-1768). The ‘Hadley Cell’, which is a circulation system in Earth’s atmosphere, is also named after him.