This image from ESA’s Mars Express show the western flank of the shield volcano Olympus Mons in the Tharsis region of the western Martian hemisphere.
The image was taken by the High Resolution Stereo Camera (HRSC) during orbit 143 from an altitude of 266 kilometres. It were taken with a resolution of about 25 metres per pixel and is centred at 222? East and 22? North. North is to the left.
The image shows the western part of the escarpment, rising from the surface level to over 7000 metres. In the foreground, part of the extensive plains west of the escarpment are shown, known as an ‘aureole’ (from the Latin for ‘circle of light’).
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To the north and west of the volcano, these ‘aureole’ deposits are regions of gigantic ridges and blocks extending some 1000 kilometres from the summit like petals of a flower. An explanation for the origin of the deposits has challenged planetary scientists for decades.
The most persistent explanation, however, has been landslides. Large masses of shield material can be found in the aureole area. Several indications also suggest a development and resurfacing connected to glacial activity.
Original Source: ESA News Release