Saturday, August 13, 2011

Recent impact near Reiner Gamma

An exaggerated close-up of an apparently unmarked pool of impact melt marking the bulls-eye floor of what must be a very fresh crater at a geologic crossroads in Oceanus Procellarum. Sampling in and around this "dig" would add to our knowledge of the Reiner Gamma albedo swirl and magnetic anomaly, the Marius Hills to the north, nearby Reiner crater and the vast Procellarum basin itself [NASA/GSFC/Arizona State University].

The small amount of impact melt pooled and froze becoming the 90 x 70 meter floor of this Copernican Age crater. What process creates impact melt pools? LROC Narrow Angle Camera (NAC) observation M111972680LE, LRO orbit 1635, November 4, 2009; image field of view is 750 meters. View the full 1500 pixel-wide LROC Featured Image HERE [NASA/GSFC/Arizona State University].

Drew Enns
LROC News System
This unnamed crater is near the Reiner Gamma Swirl in Oceanus Procellarum. The crater’s relative youth makes it a great example to investigate how impact craters form. The cratering process occurs in three stages: contact and compression, excavation, and modification. The impact melt and boulders were created during contact and compression as the bolide transferred its kinetic energy to the target.

The ejecta blanket of the unnamed crater. Image is a mosaic of NAC pair M111972680, image width is 3.0 km [NASA/GSFC/Arizona State University].

The ejecta blanket was deposited during the excavation stage, covering the surrounding mare surface with high reflectance, immature material. The modification stage brought about the final shape of the crater. As the forces involved in the impact subsided, the impact melt pooled at the bottom of the crater along with the boulders. The modification stage is still ongoing as gravity has since caused small landslides on the crater wall, and more boulders have probably eroded out of the crater wall.

Can you find similar craters in the full NAC frame?

The arrow notes the location of the relatively recent crater enfolded by the wispy anomalous albedo of Reiner Gamma, the Moon's most extensive such "swirl," in this 125 km-wide monochrome (643 nm) LROC WAC mosaic. The small crater is also situated near the end of a secondary crater chain radiant of the Reiner crater impact zone, just peaking into view at lower right. A wider field of view can be viewed HERE [NASA/GSFC/Arizona State University].

Related Posts:
Rubble Pile on Fresh Crater Floor
Action Shot
Melt and more melt

It's not inconceivable that the small but bright (optically immature) impact crater northeast of the "eye" of Reiner Gamma could be imaged from Earth. For a variety of reasons it is invisible in this spectacular mosaic captured by the Astonominsk partnership on September 25, 2008. Neither are many other lower profiled features characteristic of the Procellarum basin anatomy [Astronominsk].

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