Friday, May 6, 2011

LOLA: Drygalski of the Far South

LOLA Featured Image - It is only fitting that Drygalski Crater (diameter 149 km), located near the lunar south pole, is named for German polar scientist and geophysicist Eric Von Drygalski. LOLA data are used to examine complex craters such as Drygalski to better constrain the shape of lunar craters. High resolution topographic data from LOLA are also used to refine crater depth-to-diameter relationships for the Moon [1]. Different types of craters (simple craters, complex craters, and multi-ringed basins) have diagnostic depth-to-diameter ratios. The ratios vary for each planetary body in the Solar System due to a number of factors, including crustal density and structure as well as other characteristics of the crust.

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Traveling backward in available resolutions of Drygalski we don't lose much from the compiled LRO/LOLA laser altimetry to long polar shadow obscuring only some detail in this LROC monochrome mosaic. Note a difference in texture seen on a third of the ancient crater's floor, appearing on first glance to be an artifact of creating a mosaic of images swept up under differing sets of lighting conditions? Laser altimetry built up into the topography in the LOLA map reveals detail lost to shadow, particularly terraces within the north rim - but also that same division of landscapes on the crater floor. It's not any artifact of high latitude photography. Over the aeons, "things happened" close by and far away from Drygalski that left different traces on different parts of the crater. Note the lava pond on the south heights and the catena, a curved closely grouped chain of craters immediately to the north [NASA/GSFC/Arizona State University].

This mosaic of images in the ultraviolet (750 nm) was gathered by Clementine in 1994, swept up over a shorter period of time and from greater altitude than LRO travels today [NASA/DOD/ASU].

Priorities for the Lunar Orbiter series were scouting potential landing sites for the Apollo expeditions though the polar latitudes were photographed in unprecedented detail, providing what stood for decades as our best overhead surveys of Drygalski. Until well after the Apollo Era large areas of the Moon were undiscovered country [NASA/JPL/ASU].

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