A mound of light-coloured sulphate deposits formed from evaporating water sits inside the crater amid a sea of dark wind-blown deposits.
The darker material has blown towards the south-southwest (top left) of the image in a wide swath and across tiny craters there – their raised rims protect the material immediately downwind from being swept away.
Credit: ESA/DLR/FU Berlin (G. Neukum)
Exceptional structures deposited and shaped by water and winds adorn these interlocking craters and sculpt radiating patterns in the sands of Mars.
This mosaic, which focuses on Becquerel crater in Arabia Terra, is composed of four images taken by the high-resolution stereo camera on ESA's Mars Express.
Arabia Terra is in the transition zone between the southern highlands and the northern lowlands of Mars.
Becquerel crater is named for the 19th-century French physicist Antoine Henri Becquerel (1852–1908), winner of the Nobel Prize in physics in 1903 along with Marie and Pierre Curie for the discovery of radioactivity.
It is the largest crater in this scene, with a diameter of 167 km, and drops to a depth of about 3.5 km below the surrounding terrain.
A second large crater lies within Becquerel, punching even deeper into the surface, as seen in the Mars Express topography and 3D images.
The perspective view below reveals an intriguing, large mound within Becquerel's crater walls, reminiscent of Mount Sharp in Gale crater, currently being explored by NASA's Curiosity rover.
The mound rises about 1 km above the crater floor and comprises hundreds of layers of light-toned sediments, each just a few metres thick, made of sulphate-bearing rocks.
The main image is a mosaic of four images taken by the High Resolution Stereo Camera on ESA’s Mars Express on 22 July 2006 (orbit 3253), 26 February 2008 (orbit 5332), 2 March 2008 (orbit 5332) and 7 March 2008 (orbit 5368).
The orbit tracks and the area highlighted in the main image are indicated by the white rectangles.
Credit: NASA MGS MOLA Science Team
On Earth, sulphates are most often formed via the evaporation of water, so the presence of these minerals in Becquerel crater suggests that water may once have pooled here in a vast crater lake, before evaporating away.
It is likely that the entire crater floor was once covered with such sediments, but over billions of years much of it has been eroded away by wind, leaving just a polished, rounded mound behind.
Similar light-toned sulphate-bearing deposits are seen all over Arabia Terra, including in the crater walls in this scene, pointing to a large-scale process that affected the entire region.
One popular theory is that large changes in the tilt of the rotational axis of Mars leads to significant changes in its climate, reflected in the thickness and repeating patterns found in the layers of sediment.
A change in the environmental conditions would affect the way in which the sediments were initially deposited, as well as their subsequent resistance to erosion.
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