¹Tara S. Hayden,¹Gordon R. Osinski
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70074]
¹Department of Earth Sciences, University of Western Ontario, London, Ontario, Canada
Published by arrangement with John Wiley & Sons

Apollo sample 67015 has been classified as a fragmental breccia comprised of highlands-type clasts and is proposed to be the most complex Apollo 16 sample. 67015 is dominated by impact melt rock clasts that display a variety of textures, which have been previously interpreted to be indicative of multiple impact events. Recent modeling has indicated that the Apollo 16 regolith may contain impact basin ejecta from Nectaris, Serenitatis, Imbrium, and Orientale. Here, the textural, mineralogical, and geochemical diversity of impact melt rock clasts in several thin sections of 67015 was assessed to evaluate the provenance of these impact melts and attempt to constrain the basin ejecta emplacement at the Apollo 16 site. The petrography and mineral chemistry of the melt rock clasts is highly diverse and may indicate a variety of sources, supporting previous evidence that the Apollo 16 regolith received ejecta from numerous large impact cratering events including Imbrium and Serenitatis. The diversity of clast types observed in 67015 and textural variability of thin sections prompts discussion into the most appropriate classification of this sample as well as the nomenclature used to describe lunar melt-bearing breccia samples.

¹Karl Wimmer,²Edwin Gnos,³Beda Hofmann,⁴Sandro Boschetti,⁴Jan Walbrecker,⁴Hansruedi Maurer
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70079]
¹Independent Researcher, Nördlingen, Germany
²Natural History Museum of Geneva and Earth and Environmental Sciences, University of Geneva, Geneva, Switzerland
³Natural History Museum Bern, Bern, Switzerland
⁴Institute of Geophysics, ETH Zürich, Zürich, Switzerland
Published by arrangement with John Wiley & Sons

With a size of 51.2 × 7.2 km, the 10.9 ± 1.7 ka old Jiddat al Harasis 091 L5 chondrite strewn field is the largest known in Oman. It consists of more than 700 meteorites with a total mass of >4.5 tons from which the largest six stones of >100 kg to 1.5 tons make up two thirds of the total mass. Small stones are underrepresented, consistent with a fracturing behavior of a meteor with low shock level. Modeling yields that a bolide with 28 ± 12 tons (115 ± 15 cm radius) entered the atmosphere at a shallow angle of 22° ± 2° with a velocity of about 16 kms−1. For ~16 s, it produced a spectacular meteor along a luminous path of ~200 km length. Mass mixing within the rather straight and narrow strewn field indicates a sequence of multiple fragmentations from below 50 km down to 7 km altitude. This can be resolved adopting a wind profile from nowadays winter season, as the weather patterns with alternating Monsoon and Passat winds in the region are rather well known and repeatable since the last ice age. The largest masses with 1447 and 842 kg, respectively, produced impact breccia consisting of limestone and meteorite fragments. According to the model, the biggest mass hit the ground at a velocity of 175 ms−1 and released an impact energy of 22 MJ, corresponding to 5.3 kg TNT. This may have produced an impact crater of ~1 m diameter which, however, is not preserved. Breccia found below a much smaller mass of 68 kg deserves an explanation beyond impact energy.