HiRISE Updates Week of 2018 Oct 15

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HiRISE Updates Week of 2018 Oct 15

Post by bystander » Wed Oct 17, 2018 2:23 pm

Alfred McEwen wrote:

Dramatic Changes over the South Polar Residual Cap (ESP_056205_0935) (HiClip)

The South Polar residual cap is composed of carbon dioxide ice that persists through each Martian summer. However, it is constantly changing shape.

The slopes get more direct illumination at this polar location, so they warm up and sublimate, going directly from a solid state to a gaseous state. The gas then re-condenses as frost over flat areas, building new layers as the older layers are destroyed. This animation compares a small subarea to the same locale imaged in 2009.
Alfred McEwen wrote:

Colorful Impact (ESP_055541_1815) (HiClip)

Some regions of Mars are not very colorful, but we can be surprised by local features. This image of an impact crater in the south Syrtis Major region was acquired as a “ride-along” with a CRISM observation, which targeted this location because that instrument’s team expected a distinct composition.

Our enhanced image reveals colors ranging from red to green to blue. These are infra-red shifted colors (infrared-red-blue) so it’s different than what we would see with our eyes.
Nicole Bardabelias wrote:

Rising Above It in Amazonis Planitia (ESP_055022_2035) (HiClip)

This image shows a bright, rectangular-looking landform surrounded by a dark floor. How did this feature get here if it looks so different than its surroundings?

The feature resembles a plateau. Dark streaks mark steep slopes on its sides while the top appears flat. The slope streaks are not all the same age, as we see a variation in colors from faint to dark. Craters in a variety of sizes and ages pepper the entire rectangle, but the dark, textured floor has very few noticeable craters.

The evidence suggests that this rectangular feature is a high-standing “island” of older land surrounded by one or more younger lava flows. This landmass is located in Amazonis Planitia, a smooth plains area potentially formed by large-scale lava floods between the Tharsis and Elysium volcanic regions. As lava flowed into this area, the rectangular plateau was too high to cover completely, leaving a bright spot sticking out of the dark basalt floor for us to find.
Paul Geissler wrote:

The Pits of Elysium Mons (ESP_056026_2050) (HiClip)

During the 2018 Mars dust storm, we obtained a clear view of the summit of the giant volcano Elysium Mons. We see the western rim and floor of the caldera, and a chain of pits (called a “catena”) extending from the caldera towards the north. The chain of pits likely formed by volcanic processes, such as the collapse of a lava tube after it drained. Or by a tectonic process, such as a rift in the rocks below that drained loose material from the surface.

An unexpected feature of this catena is the presence of avalanches in two of the pits (marked A and B in the cutout, with the uphill direction towards the top of the image.) The flows in both pits could be ancient, produced during the formation of the catena, but they are not found in the other pits in the chain. They might have formed more recently by the collapse of steep dust deposits like those in a degraded crater to the left of the catena (marked C).

Credit: NASA/JPL-Caltech/University of Arizona

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