Arsia Mons Flank
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Arsia Mons Flank

April 16, 2007

This Martian image shows glacier-like flow in a depression in the flanks of Arsia Mons.

Arsia Mons is one of the large Martian volcanoes that sits near the equator on the Tharsis Rise. Downslope is towards the top left of the image, and flow is in this direction.

It is interesting to note that the depression being viewed is not directly radial from the volcano's peak, but rather oriented approximately 45 degrees away from radial, along the flanks of the volcano.

The pitted texture of the material suggests that sublimation is occurring or has occurred. Sublimation is when a substance, such as water ice, goes directly from a solid state to a gaseous state without going through an intermediate liquid phase. The surface temperature and pressure on Mars are such that water in ice-rich material can easily sublimate leaving behind a depression where the volatiles were removed.

It is possible that the flow features in this image are relict glaciers. The flow lobes and surface lineations are similar to those found on glaciers on Earth. The merging of the lobes seen in the bottom of the image and the subimage (approximately 3.2 km across) implies that multiple walls are shedding material.

It's possible that the flanks of Arsia Mons contain ice-rich material possibly deposited during a different obliquity (tilt of Mars' spin axis) or climate regime.

Observation Geometry

Image PSP_002922_1725 was taken by the High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter spacecraft on 12-Mar-2007. The complete image is centered at -7.3 degrees latitude, 236.2 degrees East longitude. The range to the target site was 276.7 km (172.9 miles). At this distance the image scale is 27.7 cm/pixel (with 1 x 1 binning) so objects ~83 cm across are resolved.

The image shown here has been map-projected to 25 cm/pixel and north is up. The image was taken at a local Mars time of 03:49 PM and the scene is illuminated from the west with a solar incidence angle of 57 degrees, thus the sun was about 33 degrees above the horizon. At a solar longitude of 198.7 degrees, the season on Mars is Northern Autumn.

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