Lunar Pioneer: Farside Boulders, Curve Northeastward

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,-
154213.034429&zoom=16&lt=LocationOverlays=llgrid,F,70;moonsunlit,F,40;satview,F,;lroc_feat_images,F,;moon_ft,F,;=InstrumentFootprints=m3_fprints,F,50;nac_fprints,F,100;=SpecialProducts=lndtmcs,F,100;lndtms,F,100;lnpole,F,100;l_lro_mrf,F,100;l_ch1_mrf,F,100;lpjnac,F,100;=M3GlobalMosaics=m3_mosaic_op2c3,F,100;m3_mosaic_op2c2,F,100;m3_mosaic_op2c1,F,100;m3_mosaic_op2b,F,100;m3_mosaic_op2a,F,100;m3_mosaic_op1b,F,100;m3_mosaic_op1a,F,100;=M3SphModelGlobalMosaics=m3_mosaic_sph_op2c3,F,100;m3_mosaic_sph_op2c2,F,100;m3_mosaic_sph_op2c1,F,100;m3_mosaic_sph_op2b,F,100;m3_mosaic_sph_op2a,F,100;m3_mosaic_sph_op1b,F,100;m3_mosaic_sph_op1a,F,100;=Basemaps=lclem_mr,F,100;wac_demclrshd2_128ppd,F,30;lnbrowse,F,100;wac_bw_v1_par,F,100;wac_bw_v1_plus_nacs,T,100;=; June 25, 2013 at 9:11 PM