Olympus Mons Caldera - detail
This image, taken by the High Resolution Stereo Camera (HRSC) on board ESA's Mars Express spacecraft, was released at the First Mars Express Science Conference this week.
This image is a close-up of the left side of the scarp in the main image (see also "Western Scarp of Olympus Mons"). This perspective view of the western side of the Olympus Mons caldera shows evidence of ice/snow and water.
On the eastern side of the giant volcano, lava produced between 200 million and 20 million years ago melted a snow and ice layer on the volcanic shield, with the result that liquid water was on the surface as recently as 20 million years ago.
On the western side, lava produced between 200 million and 2.5 million years ago mobilised underground water and formed glaciers as recently as four million years ago.