Ancient caldera in Apollinaris Patera

These images, taken by the High Resolution Stereo Camera (HRSC) on board ESA's Mars Express spacecraft, show the caldera of Apollinaris Patera, an ancient, 5-kilometre-high volcano northwest of Gusev Crater.

The HRSC obtained these images during orbit 987 with a ground resolution of approximately 11.1 metres per pixel. The images show part of Apollinaris Patera, a volcano lying at approximately 7.2° South and 174.6° East.
Apollinaris Patera is an ancient shield volcano located at the northern edge of the Southern Highlands, lying to the south-east of Elysium Planitia and to the north of Gusev Crater, which is now being explored by NASA's Mars Rover, Spirit.

The volcano measures approximately 180 by 280 kilometres at its base and rises to a maximum of 5 kilometres above the surrounding terrain.

Shield volcanos are large volcanic structures with gently sloping flanks. The caldera of Apollinaris Patera takes the form of a large crater approximately 80 kilometres in diameter and up to 1 kilometre deep. Volcanic calderas are formed when a volcano explodes or when the cone collapses.

In the true-colour image, the terrain is partly covered by thin, diffuse, whitish-appearing clouds. In the false-colour image, the clouds appear as bluish-tinted areas.

The western region of the colour image (top of the image, as north is to the right) is characterized by brighter material, which seems to be layered and could be the result of sedimentary deposition. Distinct layering, causing a terrace-like appearance, is also visible east of this brighter material and in the relatively flat region located in the northwest (top right) of the colour image.

The colour scenes have been derived from the three HRSC-colour channels and the nadir channel.

ESA News Release