Thursday, September 5, 2013


Granular fine falls on the wall of Clerke crater
Granular debris flows along the interior wall of Clerke crater, marking a stark contrast in surface reflectance. The crater floor is upper left of this approximately 2 km-wide field of view from LROC Narrow Angle Camera (NAC) observation M183332397R, LRO orbit 12116, February 8, 2012, incidence angle 43.96° full resolution 1.32 meters per pixel from 132.84 km over 20.63°N, 29.76°E [NASA/GSFC/Arizona State University].
Sarah Braden
LROC News System

The interior wall of the Clerke crater has many distinct flows of granular material which narrow as they reach towards the floor of the crater. The source material originates from the crater rim. The debris appear higher in reflectance compared to the rest of the crater wall, likely due to differences in maturity and perhaps grain size of the material.

The debris flows may be younger than the crater floor and walls if the flow was instigated by seismic shaking or a nearby impact crater. The flow may contain more boulders, which may cause the higher reflectance.

The crater is 7 km in diameter, located at 21.7°N, 29.8°E near the Taurus Littrow Valley where Apollo 17 landed on December 11, 1972 and is named after Agnes Mary Clerke.

Clerke under a high Sun, a low illumination angle of incidence (25°), resulting in an image emphasizing surface reflectance over topographic variation. From an LROC Wide Angle Camera (WAC) monochrome (566 nm) mosaic of two sequential orbital observations captured September 11, 2011; average resolution 60 meters per pixel from 41 km [NASA/GSFC/Arizona State University].
Agnes Mary Clerke was key in increasing public interest in astronomy and astrophysics. She wrote the book A Popular History of Astronomy During the Nineteenth Century (published in 1885), which was written for the non-astronomer. This publication brought her recognition from the astronomy community. Later she wrote Problems in Astrophysics which described her ideas on the direction for future research involving the Sun, stars, and nebulae. Ms. Clerke possessed a great ability to synthesize research results, look at the "big picture" of science, and communicate those ideas to the public as well as scientists. She was elected an honorary member of the Royal Astronomical Society, and an award given (at the time) to only three other women: Caroline Herschel, Mary Somerville, and Margaret Lindsay Huggins.

Sunrise topography of Clerke
Alternately, Clerke under a low Sun, and thus a high illumination angle of incidence, resulted in this view of the crater and vicinity in an image greatly emphasizing topographic variation over surface reflectance. LROC GLD100 meter per pixel mosaic, an LROC WAC context showing the proximity of Clerke to the Apollo 17 landing site (red circle) in the Taurus Littrow valley [NASA/GSFC/Arizona State University].
Explore the rest of Clerke crater and the surrounding area in the full NAC, HERE.

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