¹Amar Agarwal,¹Satyendra Kumar,²Gaurav Joshi,²K. K. Agarwal
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13604]
¹Department of Earth Sciences, Indian Institute of Technology‐Kanpur, Kanpur, 208016 India
²Centre of Advanced Study in Geology, University of Lucknow, Lucknow, 226007 India
Published by arrangement with John Wiley & Sons

The central elevated area is a postimpact morphological landmark in the otherwise flat eroded remnant of the Dhala impact structure, India. Its base is the Bundelkhand granitic complex followed by beds of Dhala and Kaimur Formations. The beds of the Dhala and Kaimur Formation present typical sedimentary textures and structures such as cross‐bedding. The grains are angular, sorting is moderate to poor, and brittle–ductile deformation of the protolith is still preserved in some grains. This reveals a short distance of transport. Detailed microscopy and U‐stage measurements confirm planar deformational features (PDFs) oriented (0001) and {10–13} in few quartz grains. Based on these facts, it is suggested that the quartz with PDFs was shocked, ejected out of the crater, and deposited near the crater cavity. Reworking of the ejecta blanket redeposited these quartz grains to their present location. Relatively few shocked grains in the rocks favor a postimpact fluvial process over impact resurge.

¹J.D.P.Deshapriya et al. (>10)
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2020.114252]
¹LESIA, Observatoire de Paris, Université PSL, CNRS, Université de Paris, Sorbonne Université, 5 place Jules Janssen, 92195 Meudon, France
Copyright Elsevier

Using data acquired by the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer) mission, we investigate spectral properties of craters on the near-Earth asteroid (101955) Bennu. We compare Bennu’s craters with its global average by means of four spectral parameters: (a) minimum position of the band at 2.7 μm, (b) depth of the hydrated phyllosilicate absorption band at 2.7 μm, (c) normalized spectral slope from 0.55 to 2.0 μm, and (d) reflectance factor at 0.55 μm. We examine 45 craters using spectral data obtained under various observing conditions. For 20 craters, we find a shortward shift of the 2.7-μm band minimum relative to the global 2.7-μm band minimum, which we attribute to the presence of relatively fresh (less space-weathered) material excavated from the sub-surface by crater-forming impacts. For three craters, we find an anti-correlation between spectral slopes and reflectance factor for a series of spectra acquired during a specific scan, where we observe that spectra become redder and darker towards the center of the crater. We attribute this to the presence of fine-particulate regolith. Localized spectral heterogeneities are apparent inside a prominent equatorial crater on Bennu, which is one of the asteroid’s oldest geological features. We propose that such local spectral heterogeneities could be used as a tracer of mass movement on Bennu. We show that younger craters are redder, brighter, and have deeper 2.7-μm bands. Comparing global average spectral values of Bennu and crater frequency distributions as a function of the chosen spectral parameters, we find that craters evolve to assume the global average spectral properties of Bennu. A positive correlation identified between the reflectance factor and 2.7-μm band depth suggests that brighter craters tend to be more hydrated. Finally, we put into context, the results from the Small Carry-on Impactor experiment by the Hayabusa2 spacecraft, which created an artificial crater on the near-Earth asteroid (162173) Ryugu.