Thursday, February 24, 2011

Dark streaks in Diophantus crater

Dark streaks down the steep inside northern rim of 19km Eratosthenian crater Diophantus (27.6°N 325.6°E) in southwest Mare Imbrium. LROC Narrow Angle Camera (NAC) frame M124797072L; 0.56 m/pixel, field of view about 678 meters, with Illumination from the south; downslope is from top to bottom. View the full-sized Featured Image HERE [NASA/GSFC/Arizona State University].

Hiroyuki Sato
LROC News System

Today's Featured Image reveals the upper slopes of Diophantus crater, located on the western edge of Mare Imbrium. The upper dark area of this image corresponds to the flat mare surface, outside of the crater. The most striking feature here is the dark material that flowed down the crater wall. The reflectance of surface materials is controlled by various factors such as sunlight direction, grain sizes and surface textures, and composition. In this picture, the dark materials are most likely a different composition (relatively bright materials also flowed down-slope next to the dark flows).

These dark features originate from several layers exposed in the crater walls. The horizontal extent of these layers is rather discontinuous and they appear at various elevations; their thickness ranges from five to ten meters. What material composes these dark slides? We know from samples returned from the Apollo 17 mission that very dark pyroclastic materials (explosive volcanics) exist on the Moon. Perhaps these slides are a layers of pyroclastics that were buried by younger lava flows. When Diophantus was formed these layers were exposed! There is much to be learned about the distribution and chemistry of pyroclastics and in turn about the deep interior of the Moon. Imagine future astronauts rappelling down to sample these exposures!

Digital Terrain Model (DTM) context map of a large area surrounding Diophantus with a rectangular strip, located at 326.34E, 27.63N. Product is from a LROC Wide Angle Camera (WAC) 100 meter-per-pixel monochrome global mosaic overlayed by WAC color DTM 500 meter-pixel survey by DLR of Germany. The rectangle corresponds to the footprint of the LROC NAC frame from which came the LROC Featured Image, February 23, 2011. View the full-sized context map HERE [NASA/GSFC/Arizona State University].

Explorer lunar landslides by viewing the full NAC frame!

The topographic color was produced as a by-product of stereo analysis of the WAC global dataset. Producing the global Digital Elevation Model (DEM) is a big job being led by LROC team members at the German Aerospace Center (DLR; English version) in Berlin.

Related Featured Images:
Color of the Moon
Volcanoes in Lacus Mortis
A Dark Cascade at Sulpicius Gallus

Foreshortened view of the LROC Featured Image (February 23, 2010) supported by the full left and right NAC frames M124797072 and the digital elevation model available to users of Google Earth (versions 5 and above) [NASA/GSFC/Arizona State University].

From the southern rim, a simulated view of the interior of Diophantus overlaid with the left and right frames of LROC NAC M124797072 and the "free air" elevation range from the dark streaked terrain just inside the crater's northern rim and the deep interior [NASA/GSFC/Arizona State University].

Diophantus, supporting Diophantus C on its southwestern rim, swept up in LROC Wide Angle Camera observation M117718865M before local sunset, from 38.8 km up during LRO orbit 2482, January 9, 2010 [NASA/GSFC/Arizona State University].

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