Dark patch enigma in Mare Smythii

Low reflectance materials splashed out from an unnamed crater, 1260 meter-wide field of view centered on 2.322°S, 81.725°E, incidence angle 3.3°   From an Narrow Angle Camera observation swept up over the far western interior of Mare Smythii, LRO orbit 19177, September 12, 2013. LROC NAC M1133662942L [NASA/GSFC/Arizona State University].

Hiroyuki Sato
LROC News System

Today's Featured Image highlights an unnamed fresh crater, about 700 meters in diameter, found on the western edge of Mare Smythii.

The low reflectance materials extend out in an distinctive bell shaped pattern from the southwestern edge of the crater rim. The interior crater wall near this deposit also shows splashes of relatively darker materials, as well as three other dark patches (at 12, 2, and 5 o'clock, relative to the crater center).

These deposits are likely similar in nature to the excavated dark deposits emplaced near the rim, and they appear to have partially flowed back into the cavity.

Enigmatic low reflectance material and surroundings in the context of the full 7.2 km width of LROC NAC observation M1133662942L [NASA/GSFC/Arizona State University].

Normally, ejecta travels radially from the impact center, resulting in lineations in the ejecta or rays pointing away from the source crater. In this bell shaped deposit, however, the two main dark lines outlining the bell are curved and extend about 150-200 m outside of the rim. Note that the surrounding terrain of this unnamed crater is nearly flat (see next WAC context); there are no readily apparent obstacles that might have affected the ejecta trajectory. Perhaps the original low reflectance deposits were unevenly buried, resulting in the curved dark patterns after excavation and final emplacement. What is the darker material? Since the crater is near the highland / mare boundary we might be seeing dark basalts or pyroclastics mixed with bright anorthositic crust.

Area of interest in LROC WAC monochrome mosaic (100 m/pix) overlayed by WAC stereo Digital Terrain Model (GLD100-DTM) false-color topography (red relatively high, blue low). Image centered at 2.22°S, 81.71°E. The LROC NAC M1333662942L footprint outlined in blue with the location of the LROC Featured Image above marked by the arrow [NASA/GSFC/Arizona State University]. 

Explore this enigmatic dark ejecta deposits in the full 7.2 km field of view of the NAC frame HERE, and find your own scenario.

Related Posts:
Dark Craters on a Bright Ejecta Blanket
Rima Bode: Constellation ROI
Dark-haloed crater in Mare Humorum
Dark halo crater
A Beautiful Impact
Pyroclastic Excavation
Dark Secondary Crater Cluster
Excavating Deposits