Lunar Reconnaissance Orbiter Camera

Frozen Motion

Image of a ray of ejecta on the Moon.
The scoured floor of Harkhebi J crater, near the young crater Giordano Bruno (22 km diameter). Ejecta from Giordano Bruno flowed across the surface, leaving a record for us to see today. LROC NAC image M1128791817L; north is up and the scene is 1.2 km wide [NASA/GSFC/Arizona State University].


Giordano Bruno, the 22 km crater whose ejecta drapes Harkhebi J, is at most 10 million years old. Because these features are so young, they are preserved almost as though the ejecta ray landed here yesterday. The Featured Image location is aproximately 5 crater radii (55 km)  away from the impact center, but the effects of the original impact are clearly visible; the momentum from the ejecta is visible as striations in the western half of the image.

The ejecta  was traveling upwards of 600 km/hr when it began to etch the surface, and when the materials finally came to rest, the evidence of the original motion was frozen in time.

LROC WAC Context Image
LROC WAC Context image. The red box indicates the full NAC image, and the yellow arrow is the aproximate Featured Image location [NASA/GSFC/Arizona State University].

Many patterns in ejecta from Giordano Bruno crater can be seen throughout the full NAC frame below. These varied beautiful patterns relate to ejecta velocity and angle, as well as the material properties of the target.

What would blocky ejecta look like? What would fine granular ejecta look like? The blocky ejecta would pepper the ground with secondary craters, while the granular ejecta would blast the existing surface smooth and flow like an avalanche. There is evidence of both in the full NAC frame below!

Ejecta from Copernicus

Outside of Giordano Bruno

Sunset Over Giordano Bruno

In the Wake of Giordano Bruno

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