¹Seamus Anderson et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13593]
Space Science and Technology Center, Curtin University, GPO Box U1987, Perth, Western Australia, 6845 Australia
Published by arrangement with John Wiley & Sons

We present a novel methodology for recovering meteorite falls observed and constrained by fireball networks, using drones and machine learning algorithms. This approach uses images of the local terrain for a given fall site to train an artificial neural network, designed to detect meteorite candidates. We have field tested our methodology to show a meteorite detection rate between 75% and 97%, while also providing an efficient mechanism to eliminate false positives. Our tests at a number of locations within Western Australia also showcase the ability for this training scheme to generalize a model to learn localized terrain features. Our model training approach was also able to correctly identify three meteorites in their native fall sites that were found using traditional searching techniques. Our methodology will be used to recover meteorite falls in a wide range of locations within globe‐spanning fireball networks.

¹Michael Anenburg,¹Antony D. Burnham,²Jessica L. Hamilton
American Mineralogist 105, 1802–1811 Link to Article [http://www.minsocam.org/msa/ammin/toc/2020/Abstracts/AM105P1802.pdf]
¹Research School of Earth Sciences, Australian National University, Canberra ACT 2600, Australia
²Australian Synchrotron, ANSTO, Clayton, Victoria 3168, Australia
Copyright: The Mineralogical Society of America

Praseodymium is capable of existing as Pr3+ and Pr4+. Although the former is dominant across almost all geological conditions, the observation of Pr4+ by XANES and Pr anomalies (both positive and negative) in multiple light rare earth element minerals from Nolans Bore, Australia, and Stetind, Norway, indicates that quadrivalent Pr can occur under oxidizing hydrothermal and supergene condi-tions. High-temperature REE partitioning experiments at oxygen fugacities up to more than 12 log units more oxidizing than the fayalite-magnetite-quartz buffer show negligible evidence for Pr4+ in zircon, indicating that Pr likely remains as Pr3+ under all magmatic conditions. Synthetic Pr4+-bearing zircons in the pigment industry form under unique conditions, which are not attained in natural systems. Quadrivalent Pr in solutions has an extremely short lifetime, but may be sufficient to cause anomalous Pr in solids. Because the same conditions that favor Pr4+ also stabilize Ce4+ to a greater extent, these two cations have similar ionic radii, and Ce is more than six times as abundant as Pr, it seems that Pr-dominant minerals must be exceptionally rare if they occur at all. We identify cold, alkaline, and oxidizing environments such as oxyhalide-rich regions at the Atacama Desert or on Mars as candidates for the existence of Pr-dominant minerals.