Luminous Pierazzo Crater

Pierazzo crater oblique
The Moon continues to surprise us with its beauty! When did this magnificent crater form? From its pristine state it looks as if it could have formed yesterday, however erosion  proceeds slowly on the Moon. NAC M1265532953LR, scene is ~11 km wide [NASA/GSFC/Arizona State University.]

This spectacular oblique image was acquired late in 2017, and required the spacecraft to roll 65° towards the limb; due to the curvature of the Moon, the viewing angle of the crater is actually 74°. This geometry is similar to viewing the distant landscape out of an airplane window, except that the Moon does not have an atmosphere that results in the hazy distant views seen on Earth. The opening image shows a reduced-scale view of the bright crater cavity and some of the ejecta. There is dark material on the crater ejecta and interior with linear and flow-like patterns. This dark material consists of lunar rocks that were melted by the very high-speed impact event, flowed in places, and then froze into dark glassy deposits.

This farside rayed crater is named after planetary scientist Elisabetta “Betty” Pierazzo (1963-2011).  Betty studied impact cratering, including the production of impact melt, so this 9.3-km diameter crater with abundant impact melt was well chosen to honor Pierazzo.  It is located within the north-northwestern extent of ejecta surrounding the Orientale impact basin.  This crater was the topic of a recent paper titled “Lobate impact melt flows within the extended ejecta blanket of Pierazzo crater” by Veronica Bray and co-authors (2018, Icarus 301, 26-36). Remarkable impact melt flows are observed from the crater’s rim and interior to more than 40 km distance. The author’s interpretation is that the melt was transported ballistically (flying above the surface) and, upon landing, separated from the solid ejecta and produced the observed flow lobes.

How old is Pierazzo crater? Scientists estimate ages of craters like this one by counting the number of smaller craters that later formed on and around the main crater. By using Zoomify (above), you can explore the entire image at full resolution and estimate the number of younger smaller craters. Be careful, some of those small superposed craters may have formed from boulders thrown out of Pierazzo crater as it formed! These are related craters are called self-secondaries. Enjoy!

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Published by Alfred McEwen on 13 February 2018