HiRISE Updates Week of 2017 Sep 18

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HiRISE Updates Week of 2017 Sep 18

Postby bystander » Thu Sep 21, 2017 5:29 pm

Sharon Wilson wrote:
A Sequence of Beauty in Terby Crater (ESP_013305_1515)

The north-facing wall of a moat-like depression in the middle of Terby Crater exposes a beautiful 400 meter-high sequence of light-toned, repetitive sedimentary layers. These deposits are often obscured by darker-toned patches of material as well as ripples and dunes.

The deposits in Terby, located on the northern rim of Hellas Planitia, are consistent with deposition in a standing body of water. The layers have been proposed as science targets for future landed missions.

Alfred McEwen wrote:
Go with the (Bright) Flow (ESP_014335_1450)

Many slopes in the middle latitudes of Mars show icy flows or glaciers. The region shown here, in the south-facing slope of a crater, is unusual because the flows have bright highlights.

The color and brightness variations are likely due to surface coatings of bright dust and dark sand. There is no evidence that these flows are currently active, but they may have been active only millions of years ago. These flows may well contain ice today in their interiors, as confirmed in places by the subsurface radar experiment on MRO.

This is a stereo pair with ESP_014058_1450.

Alfred McEwen wrote:
North Polar Layers: Streaking and Unconformity (ESP_018160_2595)

In geology, an unconformity is a buried erosion surface, where the bedding layers don’t match. It doesn’t mean a mismatch in attitudes and beliefs, with rebellious behavior like streaking. But Mars does have streaking of a different kind, from the wind.

This oblique image of part of the North Polar layered deposits, acquired in the summertime, shows both phenomena in the upper and lower panels, plus a topographic bend in the middle panel. Blue areas in this enhanced color image are covered by frost, whereas the darker colors are from differences in contamination and texture of the icy layers.

This is a stereo pair with ESP_018265_2595.

Dan Berman wrote:
Textures in Deuteronilus Mensae (ESP_018515_2225)

This enhanced color image shows the surface of a lobate debris apron in the Deuteronilus Mensae region of Mars, on the boundary between the Northern plains and Southern lowlands. These lobe-shaped formations commonly emanate from mesas in this region and have pitted, lineated textures that suggest the flow of water ice.

Results from the SHARAD (SHAllow RADar) instrument on MRO indicate that lobate debris aprons in Deuteronilus Mensae, similar to those visible here, are composed of material dominated by ice and are interpreted to be potential debris-covered glaciers or rock glaciers.

These debris apron surfaces are also covered by an ice-rich deposit that we’ve observed draping over entire regions in the mid-latitudes of Mars. It is this mantling deposit that filled in the crater, with its subsequent removal around the outer margins, probably due to differential sublimation of the ice. The same textures in the center of the crater are like those of the surrounding terrain.

Credit: NASA/JPL-Caltech/University of Arizona

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