Initial observations of lunar impact melts and ejecta flows with the Mini-RF radar

Lynn M. Carter, Catherine D. Neish, D. B.J. Bussey, Paul D. Spudis, G. Wesley Patterson, Joshua T. Cahill, R. Keith Raney

Research output: Contribution to journalArticlepeer-review

44 Scopus citations

Abstract

The Mini-RF radar on the Lunar Reconnaissance Orbiter spacecraft has revealed a great variety of crater ejecta flow and impact melt deposits, some of which were not observed in prior radar imaging. The craters Tycho and Glushko have long melt flows that exhibit variations in radar backscatter and circular polarization ratio along the flow. Comparison with optical imaging reveals that these changes are caused by features commonly seen in terrestrial lava flows, such as rafted plates, pressure ridges, and ponding. Small (<20 km) sized craters also show a large variety of deposits, including melt flows and ponds. Two craters have flow features that may be ejecta flows caused by entrained debris flowing across the surface rather than by melted rock. The circular polarization ratios (CPRs) of the impact melt flows are typically very high; even ponded areas have CPR values between 0.7 and 1.0. This high CPR suggests that deposits that appear smooth in optical imagery may be rough at centimeter-and decimeter-scales. In some places, ponds and flows are visible with no easily discernable source crater. These melt deposits may have come from oblique impacts that are capable of ejecting melted material farther downrange. They may also be associated with older, nearby craters that no longer have a radar-bright proximal ejecta blanket. The observed morphology of the lunar crater flows has implications for similar features observed on Venus. In particular, changes in backscatter along many of the ejecta flows are probably caused by features typical of lava flows.

Original languageEnglish (US)
Article numberE00H09
JournalJournal of Geophysical Research: Planets
Volume117
Issue number2
DOIs
StatePublished - 2012
Externally publishedYes

ASJC Scopus subject areas

  • Space and Planetary Science
  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)

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