Lunar Reconnaissance Orbiter Camera

Dark Splash?

Low reflectance materials splashed out from an unnamed crater. Image center is 2.322°S, 81.725°E; image width is 1260 m; incidence angle 3.3°; north is up, LROC NAC M1133662942L [NASA/GSFC/Arizona State University]. 

Today's Featured Image highlights an unnamed fresh crater (about 700 m 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 NAC context view. Image center is 2.335°S, 81.706°E, NAC 1133662942L [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.

The unnamed crater and surrounding area in LROC WAC monochrome mosaic (100 m/pix) overlayed by WAC stereo DTM (GLD100) topography (i.e. red is high, blue is low). Image center is 2.22°S, 81.71°E. The NAC footprint (blue box) and location of opening image (yellow arrow) are illustrated [NASA/GSFC/Arizona State University].  

Explore this enigmatic dark ejecta deposits in full NAC frame and find your own scenario!

Related posts:

Dark Craters on a Bright Ejecta Blanket

Rima Bode: Constellation region of interest

Dark-haloed crater in Mare Humorum

Dark halo crater

A Beautiful Impact

Pyroclastic Excavation

Dark Secondary Crater Cluster

Excavating Deposits

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