Friday, April 22, 2011

LROC: Mare Undarum 'Action Shot'

Fresh ejecta blanket of an unnamed 1 kilometer-in-diameter crater (near 7.77°N, 64.87°E, ~45 kilometers east of Firmicus C). LROC Narrow Angle Camera (NAC) observation M154813223R, LRO orbit 7949, March 15, 2011; solar incidence angle 13°, field of view 750 meters across. View the full-sized LROC Featured Image HERE [NASA/GSFC/Arizona State University].

Susan Braden
LROC News System

This small crater displays a beautiful ejecta pattern resembling a starburst. Looking at this image you can almost imagine the shower of ejecta falling to the ground.

The pattern formed out of high and low reflectance areas is due to the freshness of the ejecta. Notice in the second image that as you move away from the center of the crater, the overall reflectance of the ejecta gets lower (darker). This is because the ejecta is less continuous as you get further away from the crater.

Same NAC frame but with a larger view to show context. Notice the bouldery center of this fresh crater (zoom in HERE) and the two low albedo spots that represent secondary impacts. This image field of view is 2.2 km across. See the Full-Sized context image HERE [NASA/GSFC/Arizona State University].

There are two low reflectance (darker) spots in the ejecta, one just south of the main crater and another just west of it. If you look closely, these spots are actually small craters with their own ejecta, probably secondaries from the primary impact. They excavated material from beneath the ejecta blanket and that material has a lower albedo compared to the ejecta.

Explore the entire NAC Frame!

Related Images:
Splendors of Mare Smythii
Ejecta sweeps the surface
Delicate patterns in Giordano Bruno ejecta

40 by 74 kilometer-wide LROC Wide Angle Camera (WAC) monochrome mosaic field of view puts the bright crater and its fan of ejecta (west of direct center) in rough perspective. LROC WAC Mosaic Viewer [NASA/GSFC/Arizona State University].

Zooming out with the LROC WAC Mosaic Viewer, in turn, immediately puts the northwest quadrant of Mare Undarum (bottom) in even less granular perspective, and the fresh crater disappears amidst the Firmicus and Condorcet crater groups. The largest crater visible, northeast of center is 77 km Condorcet. Seeing just the southeastern edge of Mare Crisium at upper left, with its mountainous outer rings of mountains between itself and Undarum gives a fair indication of how far east this scene is, in line-of-sight perspective of the Moon's nearside as seen from Earth [NASA/GSFC/Arizona State University].

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