Tuesday, June 25, 2013

Farside Boulders, Curve Northeastward

Curved boulder tracks outside the rim of a fresh crater on the farside highland terrain southeast of Mare Moscoviense. LROC Narr wo Angle Camera (NAC) observation M143594908L, spacecraft orbit 6295, November 10, 2010; field of view 320 meters across, 39.27° angle of incidence, resolution 58 cm per pixel from 55.36 km [NASA/GSFC/Arizona State University].
Sarah Braden
LROC News System

The boulders in the Featured Image all curve to the northeast, carving dark paths across the fresh rays from a small 525-meter crater on the lunar farside northeast of Van Gent U, 17.233°N, 157.367°E.

The boulders originated from the impact crater itself, being ejected during the impact event with a velocity radial to the crater rim.

As the boulders bounced and rolled along the surface they lost speed (kinetic energy) and slowed, creating gently curving paths until they came to a stop.

Wider field of view from LROC NAC M143594908L, context showing the location of the boulders with respect to their source crater in a field of view 1.9 km across [NASA/GSFC/Arizona State University].
The curved paths are likely caused by the preexisting slope of the topography, which is slightly downward sloping to the northeast (~10°). The linear striations of the fresh ejecta define the radial direction away from the crater and provide a beautiful contrast for the curved boulder paths.

Using the latest LROC QuickMap, a 2.09 by 2.09 km wedge of terrain is shown in 3D, and turned 90° counter-clockwise to show the wider slope where the crater of origin and boulder field are nested in the LROC WAC-derived digital terrain model. The local elevation, from south to north ranges approximately 240 to over 900 meters above global mean [NASA/GSFC/Arizona State University]/
Overall, the fresh material was ejected at higher velocities than the boulders so it is not influenced by the topography and remains on a trajectory radial to the crater.

Explore the entire fresh crater with the LROC NAC, HERE.

Related LROC Featured Images:
Hole in One!
Bounce, Roll, and Stop
Weaving Boulder Trails on the Moon
Rolling Rolling Rolling
Sampling Schrödinger
Central Peak/Mare Boundary

1 comment:

Jay said...

Coincidentally, happened to be looking at some other nice curved examples in Thebit A’s western wall/floor (Lat 21.5772S, Long 5.0860W. Res: 0.5 m per pixel) today.

Besides the topography that would cause them to curve, as Sarah mentions, I would imagine also the shape of a boulder being more slab-like than roundish would roll/bounce on its edge like a wheel and curve slowly at the end of its journey.

John LROC reference below: http://target.lroc.asu.edu/q3/?proj=eqc&center=-654294.277323,-