Large mineralogically distinct impact melt feature at Copernicus crater – Evidence for retention of compositional heterogeneity

Abstract

Despite several lines of evidence for efficient mixing of impact melt in complex craters, we document mineralogical heterogeneity in impact melt deposit on a scale of tens of kilometers on the Moon in the 96 km‐diameter Copernicus crater. This heterogeneity is in the form of a large, sinuous impact melt feature on the floor and northern wall that is spectrally distinct from melt in its immediate vicinity. This melt feature spanning >30 km in length and 0.5–5 km in width has relatively short‐wavelength, narrow ferrous absorption bands near ~900 nm and ~2000 nm indicating a more Mg‐rich pyroxene composition as compared to impact melt deposit in the vicinity which is relatively rich in Fe/Ca‐pyroxenes. This distinction provides evidence for the preservation of compositional heterogeneity in impact melt in complex craters on the Moon and documents an example of inefficient mixing of melt during the cratering process.

Lunar surface roughness based on multiscale morphological method

“…Large melt pools appear on the surroundings of the central peaks of Tycho (95 Ma) (Krüger et al, 2013), and Jackson (150 Ma). However, the obvious melt-related variations of Copernicus (800 Ma) are just seen to the south of central peak (Dhingra et al, 2013). Based on the observation in Fig.…”

Morphometric, rheological and compositional analysis of an effusive lunar dome using high resolution remote sensing data sets: A case study from Marius hills region

“…Continuum removed spectra for the dome and adjoining regions (R1-R3) are estimated using continuum curve approximated by the straight line (approach similar to Dhingra et al, 2013) passing through the reflectance at 790 nm and 2497 nm. Reflectance curves and continuum removed spectra corresponding to these regions (spectra limited up to 2600 nm) are shown in Fig.…”

The nature and origin of Mafic Mound in the South Pole‐Aitken Basin

“…Alternatively, lunar impact melts are not always well mixed [e.g., Dhingra et al, 2013]. If large-scale mixing and convection did not occur in the SPA melt sheet, it is possible that Mafic Mound represents impact melt from a different source region than most other SPA melts (possibly involving more deep seated mantle materials).…”