Wednesday, September 3, 2014

Lovely Lichtenberg B

Lichtenberg B (4.86 km; 33.253°N, 298.48°) is a beautifully preserved young impact crater. Rock outcrops in the upper portion of the crater wall are due to the successive thin lava flows that filled Oceanus Procellarum more than 3 billion years ago. LROC NAC mosaic M1162852913LR, LRO orbit 23280, August 16, 2014; incidence angle 35.4° at 1.31 meters resolution, from 129.2 km over 32.46°N, 298.45°E [NASA/GSFC/Arizona State University].
H. Meyer
LROC News System

The lack of atmosphere on the Moon can have its benefits. For example, without an atmosphere, there are few processes to degrade landforms.

On Earth, rain and wind are major causes of erosion, but on the Moon, those causes are absent. Erosion on the Moon is due to impacts that cause shaking and can demolish other craters during formation and to gravity pulling material downslope.

In the case of Lichtenberg B, gravity has not yet rendered the crater smooth and subdued, and there are few impacts nearby, much less any that could have affected the morphology of the crater, as Lichtenberg B appears younger than its neighbors.

Extreme close-up of the wall and rim of Lichtenberg B wall and rim, just east of south center, where impact melt flowed and formed a channel, pushing boulders aside in the process. This 430 meter field of view illustrated "Lichtenberg B Flow," released December 2, 2011. LROC NAC observation M120257109R, February 8, 2010 [NASA/GSFC/Arizona State University].
On the downside, the lack of atmosphere means that space weathering is more efficient on the Moon, and fresh, highly reflective crater ejecta darkens over time. Because Lichtenberg B's ejecta deposit is still bright, it is quite young.

Lichtenberg B and about 56 km-field of view of its surroundings shows an ejecta blanket still highly visible, most than half-way through its long process of optical maturity. LROC monochrome (643 nm) observation M120256944CE, LRO orbit 2856, February 8, 2010; 54.76° incidence angle, 57.42 meters resolution, from 40.39 km [NASA/GSFC/Arizona State University].
Crisp morphology and a highly reflective ejecta deposit make Lichtenberg B stand out from many of the nearby impact craters. This exquisitely preserved crater is located to the northwest of Aristarchus Plateau in Oceanus Procellarum, a vast mare unit littered with impact craters and wrinkle ridges. The ejecta deposit is particularly interesting because it displays a wrinkled texture with structures that resemble dunes.

High-angle (late afternoon) incidence view draws some depth of field to the plains impacted by Lichtenberg B. LROC WAC monochrome (604 nm) mosaic of four observations from sequential passes December 8, 2011; 77° incidence, 56.5 meters resolution from 40 km [NASA/GSFC/Arizona State University].
How do these structures form? What makes Lichtenberg B's ejecta deposit different from other craters that lack these dune-like structures? It turns out that Lichtenberg B is not alone. Scientists have observed these same features at Linné Crater and are in the process of determining how they formed.

Forward view (north) from GRAIL-A gravity probe Ebb MoonKAM in May 2012, over northwest central Oceanus Procellarum. The maturing ejecta blanket from Lichtenberg B, Dorsum Scilla and Naumann G are in mid-foreground, with Naumann further beyond, and Naumann B (10.72 km; 37.46°N, 299.3°E) is nearer the horizon. ( MoonKAM image 133655 ) [NASA/JPL/SRSC/UCSD].
Check out the full NAC mosaic HERE.

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