Tuesday, February 1, 2011

Farside Stratified Ejecta Blocks

A stratified ejecta block around an unnamed fresh crater on the far side of the Moon, LROC Narrow Angle Camera observation M110757216R, LRO orbit 1456, October 21, 2009 (frame centered near 13.13°N, 127.61°E). Solar incidence angle is 24°, scale is 0.58 m/px [NASA/GSFC/Arizona State University].

Sarah Braden
LROC News System

An unnamed, young Copernican crater (about 8.6 km in diameter) northeast of crater Meshcherskiy, has a diverse collection of impact ejecta features. In today's featured image we see evidence for stratified materials in the ejecta blanket of the crater. This particular block, about 170 meters across (approximately two football fields long), might have formed through the impact process, or perhaps the stratified layers are consolidated (compressed) regolith. During an impact, material is thrown out of the crater cavity in sheets of material called ejecta. With the right conditions, the sheets of ejecta could form the layers of the block seen here. It is also possible that the layered material existed before the impact. The simplest explanation is that the layers we see here are actually linear stress fractures in a continuous block, due to the strength properties of the rock. Can you find similar layered rocks in other NAC images elsewhere on the Moon?

Another 80 meter-long section of ejecta, from the same crater and NAC frame appears also to have stratified layer (left side of image) [NASA/GSFC/Arizona State University].

Backing away from LROC NAC M110757216R shows debris fans falling back into the crater's interior. This close-up view of this relatively "fresh" (Copernican) crater provides the opportunity to examine lunar features before their distinctive rougher edges are pulverized by relentless bombardment by even fresher impacts, near and far, large and microscopic [NASA/GSFC/Arizona State University].

Context for the the dramatic LROC NAC frame M110757216, centered near 13°N, 127°E, 750 kilometers southwest of Mare Moscovienese [LROC WMS Image Map/Arizona State University].

Browse the rest of the ejecta blanket in the NAC frame.

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Recent Impact
Impact Melt Flows on Giordano Bruno

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