Ground hugging ejecta, northwest of Mare Orientale

Ejecta deposit of an unnamed crater  approximately 2.7 km in diameter 5 km south of this 567 meter-wide field of view centered on 9.80°N, 250.06°E. LROC Narrow Angle Camera (NAC) observation M130008764R, LRO orbit 4293, June 1, 2013; 57 cm per pixel resolution from 54.75 km, camera and spacecraft slewed 5.43° from nadir [NASA/GSFC/Arizona State University].

Hiroyuki Sato
LROC News System

Today's Featured Image highlights the northern portion of the ejecta deposit splashed from an unnamed crater (~2.7 km in diameter, about 5 km south of this image) located in the highlands ~800 km northwest of Mare Orientale. The curved stripes from the bottom toward the upper-left of this image represent the flow direction of ground hugging ejecta deposits.

As shown in the classic impact cratering model, the ejecta is ballistically sprayed out of the impact center forming an ejecta curtain. After the ejecta curtain impacts the outside of the crater, it flows in a ground hugging horizontal motion until its kinetic energy is completely dissipated. The ejecta direction depends on flow speed and the local topographic slopes or undulations.

Wider 1.8 km field of view from LROC NAC M130008764R, highlighting ejecta deposits gushed into an bowl shaped topographic low [NASA/GSFC/Arizona State University].

Nearly the same field of view with the Sun overhead results in an image that puts the emphasis on albedo over topography (see the wide context in the image below), LROC NAC M18660602LR, LRO orbit 12574, March 17, 2012; angle of incidence 8.05° at 1 meter per pixel resolution, from 120 km [NASA/GSFC/Arizona State University].

8280 meter-wide field of view from LROC NAC M186606026LR puts the highlighted topographical low in context with the source of the ejecta blanket from the fresh crater 5 km south [NASA/GSFC/Arizona State University].

Further context on the unnamed crater and surrounding ejecta from a LROC Wide Angle Camera (WAC) monochrome mosaic (100 meters per pixel) centered on 9.34°N, 250.08°E. The LROC NAC M130008764R footprint and location of the field of view shown at high resolution in the LROC Featured Image are designated [NASA/GSFC/Arizona State University].

As seen in this second image, the flow direction of ejecta curved along a bowl shaped topographic low (probably a degraded old crater). These characteristic flow lines following the local topography allows scientists to estimate the actual flow speed. In turn, these estimates elucidate detailed mechanisms of ejecta emplacement on the Moon and by comparison other airless bodies, such as asteroids and the planet Mercury

Much wider context from LROC WAC (GLD100) mosaic puts the are of interest well within the secondary bombardment ejecta originating from the basin forming impact that created Mare Orientale [NASA/GSFC/Arizona State University].

Explore these illuminating ejecta flow patterns in full NAC frame, HERE.

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