Wednesday, February 20, 2013

Dark Mantle Deposit (DMD) Excavations

Thin Skin? A patch of Dark Mantle Deposits, prominent albedo features of west and east Sinus Aestuum (southeast of Copernicus) have been over-turned by relatively recent impact, uncovering much brighter material not far below the surface. From LROC Narrow Angle Camera (NAC) observation M1103666930R, orbit 14961, September 30, 2012; resolution 94 cm per pixel. LROC Featured Image center 4.591°N, 344.348°E, field of view above is 545 meters across [NASA/GSFC/Arizona State University].
Hiroyuki Sato
LROC News System

Dark Mantle Deposits (DMDs) are diffuse deposits with a very low albedo, which are the remnants of pyroclastic eruptions. Sinus Aestuum is a DMD near Copernicus crater.

Today's Featured Image (covers) a portion of one of the lowest-reflectance areas in this DMD (see next WAC context images below), about 150 km southeast from Copernicus.

In the opening image, the lowest-reflectance materials are located at the rims and the ejecta of the multiple small craters (less than 20 meters in diameter), indicating that these dark materials are in the shallow subsurface.

Context view of western Sinus Aestuum and surrounding areas in a LROC Wide Angle Camera (WAC) monochrome mosaic centered on 4.60°N, 344.38°E. The NAC footprint (blue box) and the location of opening image field of view (yellow arrow) are indicated [NASA/GSFC/Arizona State University].
On the other hand, the two craters near the middle of this image display relatively high reflectance materials and do not expose any dark deposits from beneath the surface. That means that the lateral extent of these low-reflectance pyroclastic materials is somewhat discontinuous.  Looking at the ejecta blankets of craters within lunar DMDs is one of the best ways to estimate the extent and thickness of lunar pyroclastic deposits.  In the case of regional DMDs like Sinus Aestuum, the pyroclastic glasses that comprise these deposits represent one of the most accessible lunar resources that could be used by future human explorers to enable extended lunar surface operations.

A higher (sunrise) illumination angle normally emphasizes terrain relief over albedo, and vice versa, though in this full resolution crop from the LROC WAC mosaic (below) the contrast in local albedo are still quite evident [NASA/GSFC/Arizona State University].
The full WAC mosaic covers the western dark mantle deposit field of western Sinus Aestuum, an approximately 150 kilometers wide field of view captured over four sequential orbital passes in December 2011 [NASA/GSFC/Arizona State University].
Explore the DMDs at Sinus Aestuum in full NAC frame yourself, HERE.

Related Posts:
Pyroclastic Trails
Pyroclastics and Vent
Hyginus Crater and Pyroclastics
Pyroclastic Excavation
Rima Bode: Constellation Region of Interest

Unrelated visually, both Lunar Prospector (1998-99) and Japan's SELENE-1 (Kaguya) detected perhaps the highest rates of radioactivity stretching from Fra Mauro to west of Copernicus, represented above in a signature of Thorium. Remote sensing shows a similar, only slightly less prominent detection of Uranium, also.

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