Distal Edges

Blocky fences border an impact melt deposit on the rim of a fresh crater. LROC NAC M112884286R, image width is 816 m, illuminated from upper right, north is up [NASA/GSFC/Arizona State University].

Today's Featured Image highlights striking forms on the outside rim of an unnamed young crater (~11 km in diameter; image center 71.425°S, 161.88°E; incidence angle is 76°) located 140 km east of Schrödinger crater. The western flank of this small crater is dappled with multiple impact melt ponds (now solidified into rock) inhabiting local topographic depressions. The surfaces of the ponds show polygonal patterns of fractures that likely formed as the melt cooled and solidified (and thus shrank). The organized pattern of boulders (looking somewhat fence like) formed along a flow front. Since these lines of boulders rest on top of impact melt rocks they show that melt was splashed out at least two times during the crater forming event. The later splashes barely made it out of the crater and flowed only a short distance. What caused this last splashing of melt? Perhaps a large landslide on the interior wall fell into a lake of melt at the bottom of the crater and caused a big splash.

Short melt flows are common around lunar craters -- they tell a tale of the incredible forces unleashed during cosmic collisions. These same events happen as often on the Earth as the Moon, imagine that! But why do we see so few impact craters on the Earth? Earth has a lot of resurfacing (erosion, weathering, volcanism, plate tectonics), and weathering or resurfacing on the Moon is a lot slower. Thus, more craters and melt deposits are preserved on the Moon.

Context view of the unnamed crater and surrounding areas in LROC WAC monochrome mosaic (100 m/pix). Image center is 71.36°S, 162.91°E; image width is about 90 km; north is to the top. The NAC footprint (blue box) and the location of opening image (yellow arrow) are illustrated [NASA/GSFC/Arizona State University].

Enjoy the fascinating impact melt features around this young crater in full NAC frame!

Related posts:

Breached Levee

Splash Mark

Scalelike Impact Melts

Impact Melt Lobes

Herigonius K Impact Melt Flow


Published by Hiroyuki Sato on 27 March 2014