Starship Asterisk*

HIRISE Science Team wrote:

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Fretted Terrains and Ground Deformation (ESP_017154_1390) (HiClip)

This observation shows an excellent example of what is called "fretted terrain," termed so because of the eroded appearance of the surface.

What causes this kind of terrain? One explanation is the sublimation of subsurface ground ice that goes directly from a solid state to a gaseous one. When that occurs, the material is removed and the ground can collapse in a jumbled pattern. The curving ridges and lineations could be indicative of slow movement of the ice-rich material, perhaps in a way that has similarities to rock glaciers on Earth.

HiRISE Science Team wrote:

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Bedding Details in Layered Rock (ESP_017174_1730) (HiClip)

This beautiful image shows terrific layers and exposed bedrock along a cliff in west Candor Chasma, which is part of the extensive Valles Marineris canyon system.

A Context Camera (CTX) image of this area showed that the strata is not entirely horizontal, and that there may be crossed beds, or lenses pinching out, or some other texture/structure that might give a clue as to the depositional setting of the sediment that makes up these layers.

This image shows the area in greater detail and resolution, so we can compare what we have gleaned from CTX and MOC images to develop a better understanding of what we're looking at and how to interpret the past history of the region.

Paul Geissler wrote:

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Possible Impacts from MSL Hardware (ESP_033293_1755) (HiClip)

This cluster of small impact craters was spotted by the Context Camera on Mars Reconnaissance Orbiter in the region northwest of Gale Crater, the landing site of the Mars Science Laboratory (MSL) rover, Curiosity.

We had suspected that the cluster was produced by the impact of MSL's hardware onto the surface of Mars, because we could see it in CTX images after the landing, but it was not present in images prior to the arrival of MSL. Consistent with this interpretation is the fact that the cluster is located along a line between the Curiosity landing site and a strewn field of debris previously identified in HiRISE images as being caused by MSL hardware, in particular the cruise stage and/or tungsten weights used as cruise balance masses (see the caption for ESP_029245_1755 and associated links).

Over a year has passed since the landing, so this impact cluster is not as fresh as those imaged earlier and has been degraded somewhat by winds from the northeast. Nevertheless, the cluster shows some similarities to the impacts up-range, including asymmetric ejecta patterns that indicate an oblique impact (estimated to be only 9 to 10 degrees above horizontal). The cluster is located some 9 kilometers downrange of the impacts imaged earlier, about 70 kilometers away from the rover landing site.

With a closeup image, we see that it is was produced by a "shotgun blast" of at least 40 individual impacts that formed small craters no larger than 2 meters in diameter. In contrast, the up-range impacts included four craters that were 4 to 5 meters in diameter. Assigning each of the impacts to specific pieces of hardware is a challenging puzzle, but it is thought that the four large craters were produced by two large tungsten weights that broke in half to make these four craters, or by pieces of the cruise stage, which was designed to break up in the atmosphere for planetary protection purposes, to kill any Earthly microbes.

The cluster imaged here adds to the mystery, and may have been produced by a piece of the cruise stage that travelled farther through the Martian atmosphere and was therefore more thoroughly fragmented by the time it crashed onto the surface.

Candy Hansen wrote:

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Fall Frosting (ESP_033371_1080) (HiClip)

Richardson Crater is home to this sea of sand dunes. It was fall in the Southern hemisphere when this image was acquired and the dunes are frosted with the first bit of carbon dioxide ice condensed from the atmosphere.

As the season turns to winter ice will cover the entire dune field. At this moment however, it is patchy, and in the frost does not yet coat the ground beneath the dunes. The ground under the dunes appears to be cut by spidery troughs termed "araneiform terrain", carved by carbon dioxide sublimation (turning from solid to gas) in the spring.

Though Mars may appear to be a frozen wonderland it is not frozen in time : the spring will bring lots of activity to this region.