HiRISE Updates (2015 Feb 04)

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HiRISE Updates (2015 Feb 04)

Post by bystander » Sat Feb 07, 2015 7:50 pm

Livio Tornabene and Kayle Hansen wrote:

Tangential Craters within Ptolemaeus Crater (ESP_020065_1335) (HiClip)

This image shows two small craters, just touching on their rims, in the much larger Ptolmaeus Crater, which is located in the Martian Southern hemisphere. These craters are called “tangential craters.”

The more degraded and filled-in crater is approximately 3 kilometers in diameter, and there is an unusual feature near the center. A closeup shows up the feature is approximately 76 meters wide and 164 meters long. This feature is also possibly a substantially oblique impact crater, but its origin remains unknown.
Nathan Bridges wrote:

Curiosity Rover at Pahrump Hills (ESP_039280_1755) (HiClip)

The Mars rover Curiosity is exploring the Pahrump Hills in Gale Crater. The region contains sedimentary rocks that scientists believe formed in the presence of water. Curiosity’s recent activities have included a mini-drilling test.

Last year in December, HiRISE spied Curiosity in the Pahrump region. Zooming in, one can clearly see the rover and its shadow to the upper right. The bright features in the image are sedimentary rock and the dark areas are sand. HiRISE plans to periodically image Curiosity, as well as its companion Opportunity, as they continue to explore Mars.
Kirby Runyon wrote:

Yardangs in Arsinoes Chaos (ESP_039563_1730) (HiClip)

Several terrain types converge in this scene from Arsinoes Chaos, in the far eastern portions of Valles Marineris. The jumbled chaos terrain is likely related to the massive water-carved outflow channels that started in this area and flowed north across Mars’ hemispheric dichotomy and onto the Northern plains.

The slightly curving, sublinear bright terrain is composed of yardangs. Yardangs are portions of rock that have been sand blasted into long, skinny ridges by saltating (or bouncing) sand particles blowing in the wind.

Zooming in, you can see transverse sand ridges between the yardangs. These sand ridges are termed “transverse aeolian ridges” (TARs) and are currently not moving in Mars’ current climate. TARs are a mystery—they are mid-way in height between dunes (formed from saltating sand) and ripples (formed by “reptated” or “splashed” sand grains).
Candy Hansen wrote:

Icy Wonderland (ESP_039633_0950) (HiClip)

Although the season is late spring, carbon dioxide ice still covers much of the surface at this high latitude site. It is still a chilly -128 degrees Celsius.

The weak boundaries of the polygonal structure of the surface have been eroded by spring sublimation of carbon dioxide as energy from the Sun turns ice to gas. The larger troughs in this image accentuate the surface polygonal structure, while the narrow cracks show the erosion caused when carbon dioxide gas escapes from under the seasonal ice layer carrying fine material from the surface.

The dark fans in this image are made up of small particles from the surface deposited on top of the seasonal layer of ice. The fans originate at a crack, a weak spot that allows the gas to escape. The material is deposited in a direction determined by the direction of the wind as the gas was escaping.

Credit: NASA/JPL/University of Arizona

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