Tuesday, April 19, 2011

"How did I form?"

Small fresh crater inside the south lip of Palitzsch B (27.1°S, 68.45°E), with a shape and an ejecta pattern typical of an oblique impact. North is up, image field of view is 500 meters; LROC Narrow Angle Camera (NAC) observation M154785423R, LRO orbit 7944, March 16, 2011. See the full-sized Featured Image, HERE [NASA/GSFC/Arizona State University].

Drew Enns
LROC News System

Low angle, or oblique, impacts usually have asymmetric ejecta and form oblong craters. The typical "butterfly" ejecta pattern requires an angle of less than 15° from horizontal. This crater is quite unusual. Look closely to the south, do you see a positive relief feature? Again look north, up or down? Light is coming from the upper left, if you rotate the image 180° you might have an easier time seeing the topography correctly. Is this an oblique impact? Perhaps not, it appears an impact occurred between two boulders effecting the crater shape and ejecta pattern. This crater formed on the downhill slope of a large crater terrace. The two boulders are likely part of the slumped wall and served to deflect the ejecta mimicking the oblique impact butterfly pattern.

LROC WAC monochrome mosaic context image (LROC WAC Mosaic Viewer) of LROC News System's Featured Image, April 18, 2011. Arrow points to the oblique crater (see full-sized context image HERE); field of view ~50 kilometers [NASA/GSFC/Arizona State University].

The full NAC image provides a great view of the whole sloped wall.

Related Posts:
Asymmetric Ejecta
Bright Crater Rays and Boulders

Crop to 250 meters, full-size field of view from Lunar Reconnaissance Orbiter Camera Featured Image, April 18, 2011 [NASA/GSFC/Arizona State University].

Full-width of LROC NAC frame M154785423R [NASA/GSFC/Arizona State University].

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