Small Shield Volcano with the Caldera of Arsia Mons
Small Shield Volcano with the Caldera of Arsia Mons
PSP_008842_1705  Science Theme: Volcanic Processes
This image is centered on the vent area of a small shield volcano located within the summit caldera of Arsia Mons, the southernmost of the large three Tharsis Montes volcanoes.

Since the first details of the volcano were revealed by the Viking orbiters 30 years ago, the presence of a string of several small shield volcanoes across the floor of the caldera has been known. The resolution of the Viking images was insufficient to show more than the mere presence of small shield volcanoes and the fact that they appeared to line up along a linear trend across the floor. And, it was suspected that the small shield volcanoes were the source of the lava flows that appeared to cover the floor of the caldera, but details have been elusive.

This HiRISE image of the central small shield volcano on the caldera floor shows that there are numerous lava flows radiating from a small summit crater. To the north and south, the lavas have accumulated in lobes, some of which radiate smaller channels and lobes. About midway from the crater, to both the top and bottom of the image, the surface appears very smooth and there are few details visible. Until detailed geologic mapping is done, it is difficult to conclude whether these smooth areas represent distal ponding of lavas that erupted from the summit crater of the small shield volcano, lava flows that have invaded from outside the image area at a time later than the formation of the small shield volcano, or later deposits of dust and ash that have simply covered the surface.

Whatever the relationships, it is clear that the floor of the largest caldera on Mars is far from a bland surface of old lava flows. Numerous flows and multiple vents have all interacted to create a complex series of surfaces that record the geologic development of the caldera floor.

Written by: L. Crumpler  (23 July 2008)
Acquisition date
15 June 2008

Local Mars time

Latitude (centered)

Longitude (East)

Spacecraft altitude
244.4 km (151.9 miles)

Original image scale range
49.2 cm/pixel (with 2 x 2 binning) so objects ~147 cm across are resolved

Map projected scale
50 cm/pixel and North is up

Map projection

Emission angle

Phase angle

Solar incidence angle
60°, with the Sun about 30° above the horizon

Solar longitude
85.7°, Northern Spring

For non-map projected images
North azimuth:  97°
Sub-solar azimuth:  42.6°
Black and white
map projected  non-map

IRB color
map projected  non-map

Merged IRB
map projected

Merged RGB
map projected

RGB color
non-map projected

Black and white
map-projected   (297MB)

IRB color
map-projected   (150MB)

Black and white
map-projected  (148MB)
non-map           (189MB)

IRB color
map projected  (67MB)
non-map           (177MB)

Merged IRB
map projected  (302MB)

Merged RGB
map-projected  (303MB)

RGB color
non map           (165MB)
B&W label
Color label
Merged IRB label
Merged RGB label
EDR products

IRB: infrared-red-blue
RGB: red-green-blue
About color products (PDF)

Black & white is 5 km across; enhanced color about 1 km
For scale, use JPEG/JP2 black & white map-projected images

All of the images produced by HiRISE and accessible on this site are within the public domain: there are no restrictions on their usage by anyone in the public, including news or science organizations. We do ask for a credit line where possible:

NASA’s Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA’s Science Mission Directorate, Washington. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona.