Impact melt on the floor of Rümker E

Contact between wall, with debris flows, and the impact melt lens inundating the floor of Rümker E, immediately southeast of the landmark Mons Rümker ridge extrusion mound in north Oceanus Procellarum. Area detail covered in the LROC Featured Image released March 8, 2013. LROC Narrow Angle Camera (NAC) observation M122591558L, spacecraft orbit 3200, March 7, 2010; angle of incidence 42.68° at 0.5 meters resolution from 40.63 km [NASA/GSFC/Arizona State University].

LROC Featured Image, March 8, 2013: Close up on the full width of the impact melt deposit on the floor of Rümker E, in an approximately 2 km wide field of view from LROC NAC M1101573334L, LRO orbit 14668, September 6, 2012; angle of incidence 41.16° at 1.13 meters resolution, from 152.92 km  [NASA/GSFC/Arizona State University].

Sarah Braden
LROC News System

Imagine a quiet afternoon on the lunar surface about 1 billion years ago. Suddenly, the ground shakes due to the shock wave from a nearby impact.

You see rock and dust burst away from the ground on ballistic trajectories, and some large chunks of material contain so much energy from the impact, they are glowing with heat.

Some of the molten rock splashes outside the rim, but most remains on the floor of the newly formed crater, creating an impact melt deposit.

The crater Rümker E (38.620°N, 302.881°E) is a simple Copernican-aged crater with a diameter of 6.96 km.

Two LROC Wide Angle Camera (WAC) mosaics show different sun angles. Above, the sun angle is higher, so the high reflectance rays of the crater are more visible, and below the sun angle is lower, emphasizing the morphology of the surface [NASA/GSFC/Arizona State University].

Impact melt in the crater floor is fresh with common features such as fractures, boulders, and mounds. The fractures are mostly located around the edges of the impact melt deposit and formed either as the impact melt cooled, or after cooling during the stage of crater modification due to stresses in the crater floor. Over time the granular material falling down the crater walls will slowly cover more and more of the impact melt deposit, decreasing its diameter. Compositionally, the impact melt is a combination of the rocks present in the target material. In this case, the target material is mostly mare basalt.

Rümker E in relation to Mons Rümker, a wide volcanic shield mound showing sighs of long-term episodic, if not particularly violent, periods of activity; a extraordinary formation easily seen at high angles along the telescopic line of sight from Earth. LROC WAC monochrome (643nm) mosaic [NASA/GSFC/Arizona State University].

Explore the entire NAC frame, HERE.

Check out these previous posts for more examples of beautiful impact melt features:
Lineations on the Melt
Dynamics of Molten Rocks
Sunny Side Up

The wrinkled morphology and ridges of north Oceanus Procellarum, including compositional differences between the mare terrain and Mons Rümker (above left from center), are more difficult to detect when the Sun is high, but when the terminator passes and the Sun is low, the anatomy is stark. from HDTV still captured by Japan's lunar orbiter SELENE-1 (Kaguya) in 2008 [NASA/GSFC/Arizona State University].