Wednesday, October 26, 2011

LROC: Posidonius Y marks the spot

A boulder perched on the north rim of a Copernican Age crater situated directly atop the Dorsa Smirnov wrinkle ridge in Mare Serenitatis. LROC Narrow Angle Camera (NAC) observation M168041107L, LRO Orbit 9898, August 15, 2011; resolution 0.25 meters per pixel, width of the field of view is only 145 meters [NASA/GSFC/Arizona State University].

Sarah Braden
LROC News System

Posidonius Y is a 2 km diameter Copernican Age crater located at 30.04°N, 29.4°E, in the upper northeast section of Mare Serenitatis. The crater is remarkably bouldery, which is a indication of a relatively young age. The boulder seen on the rim in today's Feature Image is about 25 meters long from stem to stern (about half the length of an Olympic sized swimming pool).

Since Posidonius Y is superposed on the wrinkle ridge system known as Dorsa Smirnov, the crater is also relatively younger than these tectonic features. The WAC context image below shows the beautiful combination of mare basalt volcanism, tectonics, and impact cratering that shape the lunar surface.

Reduction from a 60 meter per pixel 604 nm mosaic from LROC Wide Angle Camera (WAC) observations in LRO Orbits 4502 - 4512, June 17 - 18, 2010. Posidonius Y is aptly named,  at a "Y" shaped intersection of the Dorsa Smirnov wrinkle ridge system in northeast Mare Serenitatis[NASA/GSFC/Arizona State University].

The bright crater is not quite visible, though the Y in Dorsa Smirnov at lower center, in northeast Mare Serenitatis where it's perched (just west of its complex namesake, this is a typical amateur telescopic view of the Moon six and a half days after a New Moon. This is the first of two opportunities to view the ridge system, in the long shadows of local morning and evening. Between, under a higher Sun, the bright ejecta field stands out as the subtle ridge system fades into the background.

Explore the entire NAC frame!

Related Images:
Layers in Lucian Crater
Farside Impact!
Recent Impact in Oceanus Procellarum

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