HiRISE Updates Week of 2017 July 10

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HiRISE Updates Week of 2017 July 10

Post by bystander » Mon Jul 17, 2017 3:25 pm

Livio L. Tornabene, Jon Kissi, Zach Morse and Gavin Tolometti wrote:

Escape from Mars! (ESP_050250_1915) (HiClip)

This image shows one of millions of small (10s of meters in diameter) craters and their ejecta material that dot the Elysium Planitia region of Mars. The small craters were likely formed when high-speed blocks of rock were thrown out by a much larger impact (about 10-kilometers in diameter) and fell back to the ground.

Some of these blocks may actually escape Mars, which is how we get samples in the form of meteorites that fall to Earth. Other ejected blocks have insufficient velocity, or the wrong trajectory, to escape the Red Planet. As such, when one of these high-speed blocks impacts the surface, it makes what is called a “secondary” crater. These secondaries can form dense “chains” or “rays”, which are radial to the crater that formed them.

Tycho Crater is an excellent example of a “rayed crater” that shows rays that span the entire near-side of the Moon.
Livio L. Tornabene, Jon Kissi, Zach Morse and Gavin Tolometti wrote:

Dragon Scales of Mars (ESP_050275_1500) (HiClip)

This intriguing surface texture is the result of rock interacting with water. The rock was then eroded and later exposed to the surface. The pinkish, almost dragon-like scaled texture represents Martian bedrock that has specifically altered into a clay-bearing rock.

The nature of the water responsible for the alteration, and how it interacted with the rock to form the clay remains poorly understood. Not surprisingly, the study of such altered rocks on Mars is an area of active investigation by the Mars science community. Understanding such interactions, and how they happened, help scientists to understand the past climate on Mars, and if the red planet ever harbored life.

Recent studies indicate that the early Martian climate may not have been as warm, wet, and Earth-like, as previously suggested. This is not a problem for finding life on Mars as one might think. Ongoing studies of dry and cold environments on Earth shows that life finds ways to adapt to such extremes. Such work provides hope for finding evidence for life on other planets, like Mars, someday.
Gavin Tolometti, Livio L. Tornabene and Jon Kissi wrote:

Mars and the Amazing Technicolor Ejecta Blanket (ESP_050281_1505) (HiClip)

A close-up image shows the exposed bedrock of an ejecta blanket of an unnamed crater in the Mare Serpentis region of Mars. Ejecta, when exposed, are truly an eye-opening feature, as they reveal the sometimes exotic subsurface, and materials created by impacts. This ejecta shares similarities to others found elsewhere on Mars, which are of particular scientific interest for the extent of exposure and diverse colors. (For example, the Hargraves Crater ejecta, in the Nili Fossae trough region, was once considered as a candidate landing site for the next NASA Mars rover 2020.

The colors observed in this picture represent different rocks and minerals, now exposed on the surface. Blue in HiRISE infrared color images generally depicts iron-rich minerals, like olivine and pyroxene. Lighter colors, such as yellow, indicate the presence of altered rocks.

The possible sources of the ejecta is most likely from two unnamed craters. How do we determine which crater deposited the ejecta?

A full-scale image shows numerous linear features that are observed trending in an east-west direction. These linear features indicate the flow direction of the ejecta from its unnamed host crater. Therefore, if we follow them, we find that they emanate from the bottom of the two unnamed craters. If the ejecta had originated from the top crater, then we would expect the linear features at the location of our picture to trend northwest to southeast.
Jon Kissi, Livio L. Tornabene and Eric Pilles wrote:

The “Specters” of Mars (ESP_050347_1130) (HiClip)

The jagged saw-tooth dichotomy, over a grainy texture, seen in this close-up image, reminds us of a scene from an old silent horror movie. Stark and unnerving, like that time between dusk and darkness, as the campfire burns out...was that something moving you saw through the canvas of your tent?

Malea Planum is a polar region in the Southern hemisphere of Mars, directly south of Hellas Basin, which contains the lowest point of elevation on the planet. The region contains ancient volcanoes of a certain type, referred to as “paterae.” Patera is the Latin word for a shallow drinking bowl, and was first applied to volcanic-looking features, with scalloped-edged calderas. Malea is also a low-lying plain, known to be covered in dust. These two pieces of information provide regional context that aid our understanding of the scene and features contained in our image. The area rises gradually to a ridge (which can be seen in this Context Camera image) and light-colored dust is blown away by gusts of the Martian wind, which accelerate up the slope to the ridge, leading to more sharp angles of contact between light and dark surface materials.

Of course, in keeping with age old stories of the supernatural powers of creatures of the night, Martian dust devils are able to move with impunity all the way up the slope. The tell-tale traces of their passage are visible as haphazard dark streaks crossing the area, like specters drifting through the night.

Credit: NASA/JPL-Caltech/University of Arizona

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