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Bright Layered Deposits January 16, 2010

Posted by jtintle in Planets, Space Fotos.
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Mars

Description:

Martian landforms have been shaped by winds, water, lava flow, seasonal icing and other forces over millennia. This view shows color variations in bright layered deposits on a plateau near Juventae Chasma in the Valles Marineris region of Mars. A brown mantle covers portions of the bright deposits. Researchers have found that these bright layered deposits contain opaline silica and iron sulfates.

Image Credit:

NASA/JPL-Caltech/University of Arizona

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North Polar Layered Deposits in Head Scarp of Chasma Boreale January 9, 2010

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North Polar Layered Deposits in Head Scarp of Chasma Boreale

Credit:

NASA/JPL/University of Arizona, Ken Herkenhoff

Description:

This false-color subimage shows the north polar layered deposits at top and darker materials at bottom exposed in a scarp at the head of Chasma Boreale, a large canyon eroded into the layered deposits.

The polar layered deposits appear red because of dust mixed within them, but are ice-rich as indicated by previous observations. The water ice in the layered deposits is probably responsible for the pattern of fractures seen near the top of the scarp.

The darker material below the layered deposits may have been deposited as sand dunes, as indicated by the cross-bedding (truncation of curved lines) seen near the middle of the scarp. It appears that brighter, ice-rich layers were deposited between the dark dunes in places.

Exposures such as these are useful in understanding the recent climate variations that are likely recorded in the polar layered deposits.

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NGC 6960: The Witch’s Broom Nebula August 28, 2008

Posted by jtintle in Deep Space, Space Fotos.
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See Explanation.  Clicking on the picture will download  the highest resolution version available.

Credit & Copyright:

Adam Block, Mount Lemmon SkyCenter, Univ. Arizona

Explanation:

Ten thousand years ago, before the dawn of recorded human history, a new light must suddenly have appeared in the night sky and faded after a few weeks. Today we know this light was an exploding star and record the colorful expanding cloud as the Veil Nebula. Pictured above is the west end of the Veil Nebula known technically as NGC 6960 but less formally as the Witch‘s Broom Nebula. The expanding debris cloud gains its colors by sweeping up and exciting existing nearby gas. The supernova remnant lies about 1400 light-years away towards the constellation of Cygnus. This Witch’s Broom actually spans over three times the angular size of the full Moon. The bright star 52 Cygni is visible with the unaided eye from a dark location but unrelated to the ancient supernova.

Fresh Double-Layered Ejecta Crater (PSP_009160_2350) August 25, 2008

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Fresh Double-Layered Ejecta Crater

Credit:

NASA/JPL/University of Arizona

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Explanation:

This scene features a high latitude, northern hemisphere crater with double-layered ejecta. The sharp rim and lack of small superposed craters indicates that this crater is relatively young.

The semi-circular feature that parallels the crater rim is a terrace that probably formed as part of the crater wall collapsed into the center. The circular mound in the center likely formed at the same time as the crater itself. Large craters on Mars can have central peaks; this crater looks like it was on the cusp of having one. The linear features surrounding the crater on its ejecta are striations that formed during the impact as material and wind exploded out from the center.

At the bottom of the scene is a very distinct ejecta flow lobe (lobate ejecta). Lobate ejecta is thought to form when an impact occurs on a surface with lots of volatiles—ices that quickly turn to gas when they are heated. The gases help make the ejecta flow like a fluid.

Polygons, Crater Layers, and Defrosting Dunes (PSP_008426_2595) June 30, 2008

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Polygons, Crater Layers, and Defrosting Dunes

Credit:

NASA/JPL/University of Arizona

Description:

The north polar region is surrounded by a large sea (erg) of dark sand dunes that become covered by seasonal carbon dioxide frost. As the northern hemisphere begins to warm in the spring, the frozen carbon dioxide sublimates. The wind blows from an east-northeasterly direction and leaves dark streaks behind (exposed basalt) from the evaporating carbon dioxide. This image displays defrosting sand dunes in an unnamed crater.

The dune morphology in this image is complex. Because of the presence of the ice, it is difficult to determine all of the dune types. These jumbled dunes may result from erosion of the layers within the crater walls that act as a dune source.. However, two common types of dunes can be classified: the outer ring of the dune field is composed of chains of barchan dunes whereas the central area of the field contains transverse dunes.

Barchans are characterized by their crescent-shape with steep horns in the downwind direction. The transverse dunes have asymmetric, nearly parallel ridges and are oriented perpendicular to the wind direction.

Another feature of interest is the sublimating polygons that have very small ripples on top of them. Polygons are created from a freeze-thaw processes similar to features on Earth that undergo annual contraction of the permafrost regolith.

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PIA09097: Layers Exposed at Polar Canyon January 6, 2007

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Layers Exposed at Polar Canyon

Credit:

NASA/JPL-Caltech/Univ. of Arizona

Description:

This false-color subframe of an image from the High Resolution Imaging Science Experiment camera on NASA’s Mars Reconnaissance Orbiter shows the north polar layered deposits at top and darker materials at bottom, exposed in a scarp at the head of Chasma Boreale, a large canyon eroded into the layered deposits.

The polar layered deposits appear red because of dust mixed within them, but are ice-rich as indicated by previous observations. Water ice in the layered deposits is probably responsible for the pattern of fractures seen near the top of the scarp. The darker material below the layered deposits may have been deposited as sand dunes, as indicated by the crossbedding (truncation of curved lines) seen near the middle of the scarp. It appears that brighter, ice-rich layers were deposited between the dark dunes in places. Exposures such as these are useful in understanding recent climate variations that are likely recorded in the polar layered deposits.

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