vendredi 4 décembre 2015

Pluto's Layered Craters and Icy Plains & Mountainous Shoreline of Sputnik Planum












NASA - New Horizons Mission logo.

Dec. 4, 2015

Pluto's Layered Craters and Icy Plains

This highest-resolution image from NASA’s New Horizons spacecraft reveals new details of Pluto’s rugged, icy cratered plains. Notice the layering in the interior walls of many craters (the large crater at upper right is a good example). Layers in geology usually mean an important change in composition or event, but at the moment New Horizons team members do not know if they are seeing local, regional or global layering. The darker crater in the lower center is apparently younger than the others, because dark material ejected from within – its “ejecta blanket” – has not been erased and can still be made out. The origin of the many dark linear features trending roughly vertically in the bottom half of the image is under debate, but may be tectonic. Most of the craters seen here lie within the 155-mile (250-kilometer)-wide Burney Basin, whose outer rim or ring forms the line of hills or low mountains at bottom. The basin is informally named after Venetia Burney, the English schoolgirl who first proposed the name “Pluto” for the newly discovered planet in 1930. The top of the image is to Pluto’s northwest.

The Mountainous Shoreline of Sputnik Planum

In this highest-resolution image from NASA’s New Horizons spacecraft, great blocks of Pluto’s water-ice crust appear jammed together in the informally named al-Idrisi mountains. Some mountain sides appear coated in dark material, while other sides are bright. Several sheer faces appear to show crustal layering, perhaps related to the layers seen in some of Pluto’s crater walls. Other materials appear crushed between the mountains, as if these great blocks of water ice, some standing as much as 1.5 miles high, were jostled back and forth. The mountains end abruptly at the shoreline of the informally named Sputnik Planum, where the soft, nitrogen-rich ices of the plain form a nearly level surface, broken only by the fine trace work of striking, cellular boundaries and the textured surface of the plain’s ices (which is possibly related to sunlight-driven ice sublimation). This view is about 50 miles wide. The top of the image is to Pluto’s northwest.

For more information about New Horizons, visit: http://www.nasa.gov/mission_pages/newhorizons/main/index.html

Images, Text, Credits: NASA/JHUAPL/SwRI/Tricia Talbert.

Best regards, Orbiter.ch

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