|Northeastern edge of a high-reflectance mound within "driving distance" of the Apollo 15 landing site on the southeastern frontier of Mare Imbrium. Downslope is to the upper-right. (Field of view 1512 meters across). LROC Narrow Angle Camera (NAC) observation M106869873R, LRO orbit 890, September 6, 2009; resolution 1.26 meters per pixel, incidence angle 36.72° from an altitude of 153.64 kilometers. View the much larger, full size LROC Featured Image HERE [NASA/GSFC/Arizona State University].|
LROC News System
At the southeastern edge of Mare Imbrium, about 25 km west of Rima Hadley, there is a small shiny mound on a dark and flat mare basalt plain which looks like a white sand island in the middle of a black ocean. This mound is about 2.7 by 2.2 km across.
Normally fresh slopes and fresh ejecta have high reflectance due to less space weathering but this mound is brightest at its highest elevations and not down the slopes, brighter than nearby ejecta implying the mound is composed of higher-reflectance materials than mare basalts. Then how was this shiny island was formed?
|Whole view of high-reflectance mound centered at 25.482°N, 1.684°E (Field of view about 5.3 kilometers. See the original LROC context image HERE, also from LROC NAC frame M106869873R [NASA/GSFC/Arizona State University].|
Most likely, the mound is a remnant of highlands sticking through the mare, a hummock of plagioclase-rich highlands materials was embayed by mare basalt volcanism, burying all except its summit. If so, mare basalt is overlapping the mound's skirt.
Can you see the an overlap contact in today's Featured Image?
|An oblique view from a simulated low altitude looking northeast over the LROC WAC 100 m monochrome Global Mosaic affixed to LOLA topography, using NASA's ILIADS program. The bright mound is near the center of the view, with the Hadley Rille Valley and the landing site of Apollo 15 in the background. Does the angle of this view seem familiar? [NASA/GSFC/Arizona State University].|
Unfortunately, the contact is not clear or sharp. Over time such sharp contacts are blurred by micrometeorite bombardment. If we are lucky, in the future, a small impact may occur right at the contact once again revealing the sharp contact. Or perhaps a future explorer might take a shovel to this spot and settle the question!
Explore this shiny mound in the full NAC image!
Farside Highlands Volcanism!
Up from the depths
Hortensius Domes - Constellation ROI
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