Last updated on April 21, 2014 at 7:52 EDT
Tongue-Shaped Flow Feature
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Tongue-Shaped Flow Feature

February 21, 2007

This image captures a tongue-shaped lobate flow feature along a interior crater wall located in eastern Hellas Planitia.

The flow feature is approximately 5 kilometers long and 1 kilometer wide with a partial double inner ridge and raised outer margin. The flow feature's surface is generally devoid of impact craters and parts of its outer margin have deflected around obstacles.

Similar flow features, though not as distinctively tongue-shaped as this one, are found in many other craters throughout the southern mid-latitudes of Mars.

Recent studies of these flow features have determined a latitudinal dependence to which side of the crater interior these features are formed upon. For this particular flow feature, it has formed on the pole-facing slope. This polar or equatorial-facing preference has implications for the amount of solar isolation these slopes are receiving, which may be a result of recent climate change due to shifts from low to high obliquity.

Although these Martian flow features may have Earth analogs such as rock glaciers, uncertainty remains as to what types of fluvial, glacial and mass-wasting processes are involved in their formation. This particular flow feature was imaged previously by the Mars Orbiter Camera (MOC) onboard NASA's Mars Global Surveyor spacecraft.

Observation Geometry

Image PSP_002320_1415 was taken by the High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter spacecraft on 24-Jan-2007. The complete image is centered at -38.1 degrees latitude, 113.2 degrees East longitude. The range to the target site was 255.2 km (159.5 miles). At this distance the image scale is 25.5 cm/pixel (with 1 x 1 binning) so objects ~77 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 03:46 PM and the scene is illuminated from the west with a solar incidence angle of 67 degrees, thus the sun was about 23 degrees above the horizon. At a solar longitude of 171.9 degrees, the season on Mars is Northern Summer.