Impact cratering is the dominant process for transporting material on the Moon's surface. An impact transports both proximal material (continuous ejecta) locally and distal ejecta (crater rays) to much larger distances. Quantifying the relative importance of locally derived material versus distal material requires understandings of lunar regolith evolution and the mixing of materials across the lunar surface. The Moon has distinctive albedo units of darker mare basalt and brighter highland materials, and the contacts between these units are ideal settings to examine this question. Information on the amount of material transported across these contacts comes from both the sample collection and remote sensing data, though earlier interpretations of these observations are contradictory. The relatively narrow (~4–5 km wide) mixing zone at mare/highland contacts had been interpreted as consistent with most material having been locally derived from underneath mare plains. However, even far from these contacts where the mare is thick, highland material is abundant in some soil samples (>20%), requiring transport of highland material over great distances. Any model of impact transport on the Moon needs to be consistent with both the observed width of mare/highland contacts and the commonality of nonmare material in mare soil samples far from any contact. In this study, using a three‐dimensional regolith transport model, we match these constraints and demonstrate that both local and distal material transports are important at the lunar surface. Furthermore, the nature of the distal material transport mechanism in discrete crater rays can result in substantial heterogeneity of surface materials.

The distributions of 40 Ar/ 39 Ar-derived ages of impact glass spherules in lunar regolith samples show an excess at <500 Ma relative to older ages. It has not been well understood whether this excess of young ages reflects an increase in the recent lunar impact flux or is due to a bias in the samples. We developed a model to simulate the production, transport, destruction, and sampling of lunar glass spherules. A modeled bias is seen when either (1) the simulated sampling depth is 10 cm, consistent with the typical depth from which Apollo soil samples were taken, or (2) when glass occurrence in the ejecta is limited to >10 crater radii from the crater, consistent with terrestrial microtektite observations. We suggest that the observed excess of young ages for lunar impact glasses is likely due to limitations of the regolith sampling strategy of the Apollo program, rather than reflecting a change in the lunar impact rate.Plain Language Summary Lunar regolith samples collected by the Apollo astronauts contain impact glass spherules that record the age of formation in the Ar-Ar isotope dating system. There are as many spherules with measured ages within the last 500 million years as there is in the previous 4 billion years of lunar history, and it has remained a mystery as to whether this is because the impact rate was higher in the recent past, or if there was some process that was biasing these samples toward a young age. We have developed a three-dimensional computer model that simulates the production, transport, destruction, and sampling of impact-generated glass spherules on the Moon. Using reasonable assumptions that are backed up from data on Earth craters, we are able to reproduce the observed excess of young spherule ages seen in the Apollo samples assuming that impact rate has not changed over the last three billion years. We find that the young age bias is only seen because the Apollo samples were collected in the upper few centimeters of the lunar surface. Future glasses collected from the upper few meters of the surface should have ages that better reflect the true rate of impacts over time.

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Although the application of nanotechnology to drug therapy has been widely investigated, very few nanomedicine-based treatments for traumatic hemorrhage have been reported so far. The aim of this work was to develop nanostructured lipid carriers (NLCs) loaded with phosphodiesterase 4 (PDE4) inhibitors to treat acute inflammation in peripheral organs. The pharmacokinetics and biodistribution of DSM-RX78 and EFB-1, two novel PDE4 inhibitors, were examined using rats as an animal model. Entrapment by NLCs resulted in sustained drug release. The plasma concentrations of DSM-RX78 and EFB-1 in NLCs were lower, and their half-lives were much shorter in the NLC condition than in the control condition. PDE4 inhibitors delivered in NLCs accumulated with high abundance in many organs, especially the brain and lungs. Polyethylene glycol (PEG) coating on the particulate surface (P-NLCs) significantly reduced brain delivery of the drugs. P-NLCs enhanced drug distribution to the lungs by 5-fold compared to free control. In vivo real-time imaging confirmed rapid escape of nanoparticles from the blood circulation. Histological examination and aminotransferase measurement revealed that P-NLCs containing EFB-1 improved hemorrhagic shock-induced injuries in the lungs, intestines, and liver. P-NLCs even reversed acute lung inflammation to the level observed in an uninjured condition. Our results indicate that NLC-based delivery of PDE4 inhibitors is a candidate treatment for traumatic hemorrhage.

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