¹John H.D.Harrison,^1,2Oliver Shorttle,¹Amy Bonsor
Earth and Planetary Science Letters 554, 116694 Link to Article [https://doi.org/10.1016/j.epsl.2020.116694]
¹Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA, UK
²Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EQ, UK
Copyright Elsevier

The loss and gain of volatile elements during planet formation is key for setting their subsequent climate, geodynamics, and habitability. Two broad regimes of volatile element transport in and out of planetary building blocks have been identified: that occurring when the nebula is still present, and that occurring after it has dissipated. Evidence for volatile element loss in planetary bodies after the dissipation of the solar nebula is found in the high Mn to Na abundance ratio of Mars, the Moon, and many of the solar system’s minor bodies. This volatile loss is expected to occur when the bodies are heated by planetary collisions and short-lived radionuclides, and enter a global magma ocean stage early in their history. The bulk composition of exo-planetary bodies can be determined by observing white dwarfs which have accreted planetary material. The abundances of Na, Mn, and Mg have been measured for the accreting material in four polluted white dwarf systems. Whilst the Mn/Na abundances of three white dwarf systems are consistent with the fractionations expected during nebula condensation, the high Mn/Na abundance ratio of GD362 means that it is not (). We find that heating of the planetary system orbiting GD362 during the star’s giant branch evolution is insufficient to produce such a high Mn/Na. We, therefore, propose that volatile loss occurred in a manner analogous to that of the solar system bodies, either due to impacts shortly after their formation or from heating by short-lived radionuclides. We present potential evidence for a magma ocean stage on the exo-planetary body which currently pollutes the atmosphere of GD362.

¹K. Righter,²R. Rowland II,²L. R. Danielson,³M. Humayun,³S. Yang,
⁴N. Mayer (Waeselmann),⁵K. Pando
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13598]
¹NASA Johnson Space Center, Mailcode XI2, 2101 NASA Parkway, Houston, Texas, 77058 USA
²Los Alamos National Laboratory, Mail Stop P952, Los Alamos, New Mexico, 87545 USA
³National High Magnetic Field Laboratory, and Department of Earth, Ocean & Atmospheric Science, Florida State University, Tallahassee, Florida, 32310 USA
⁴Mineralogisch‐Petrographisches Institut (MPI), University of Hamburg, Grindelallee, 48, 20146 Hamburg, Germany
⁵Jacobs JETS, 2101 NASA Parkway, NASA Johnson Space Center, Houston, Texas, 77058 USA
Published by arrangement with John Wiley & Sons

Trace elements and extant and extinct isotopic attributes in Martian meteorites have been used to argue that Mars accreted quickly, differentiated into core and mantle, and established several mantle reservoirs, possibly within 10 Ma of T0. The partitioning of trace elements in the deep mantle has been relatively unstudied, despite the need for such knowledge in understanding magma ocean crystallization and the origin of depleted and enriched mantle reservoirs. The siderophile element composition of the Martian mantle and lithophile isotopic systems such as Sr, Hf, and Nd are thought to record evidence for early metal–silicate equilibrium and deep magma ocean at an intermediate depth and pressure of 800 km or 14 GPa. We have carried out experiments across this pressure range to better understand the mineral/melt partitioning of a wide range of elements. These new data are used to evaluate differentiation models for Mars and to help interpret the available isotopic data. The relatively incompatible nature of Re compared to mildly compatible Os means that the crystallization of a deep magma ocean will lead to residual liquids with superchondritic Re/Os, and solids with subchondritic Re/Os. Such material available in the mantle could be the source of enriched isotopic reservoir that produced shergottites with +γOs values. Slightly subchondritic Re/Os ratios in the crystallizing solids would provide a reservoir that could produce −γOs values. Melting of mixtures of these two enriched and depleted endmembers could explain the Nd‐Os isotopic correlations and systematics of shergottites.

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.

¹Atencio, D.,¹Cunha, D.,²Ribeiro Moutinho, A.L.,³Zucolotto, M.E.,¹Tosi, A.A.,³Nassif Villaça, C.V.
Brazilian Journal of Geology 50, 2020 Link to Article [DOI: 10.1590/2317-4889202020190085]
¹Universidade de São Paulo, São Paulo (SP), Brazil
²International Meteorite Collector Association, Jacareí (SP), Brazil
³Universidade Federal do Rio de Janeiro, Rio de Janeiro (RJ), Brazil

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

¹Maximilian P.Reitze,¹Iris Weber,¹Andreas Morlok,¹Harald Hiesinger,¹Karin E.Bauch,¹Aleksandra N.Stojic,²Jörn Helbert
Earth and Planetary Science Letters 554, 116697 Link to Article [https://doi.org/10.1016/j.epsl.2020.116697]
¹Institut für Planetologie, Westfälische Wilhelms-Universität (WWU) Münster, 48149 Münster, Germany
²Deutsches Zentrum für Luft- und Raumfahrt (DLR), Rutherfordstr. 2, 12489 Berlin, Germany
Copyright Elsevier

We analyzed plagioclase feldspar samples that were well-characterized in terms of chemical composition as well as degree of Al,Si order in mid-infrared reflection spectra between 7 μm and 14 μm (1429 cm−1 and 714 cm−1). The chemical compositions were derived with an electron microprobe analyzer. To determine the degree of Al,Si order, powder X-ray diffraction methods were applied. For the interpretation of the infrared spectra, we used the wavelength of the Christiansen feature (CF) and the autocorrelation function for a specific wavelength region. The CF shifts from around 7.72 μm (1296 cm−1) in Na-richest samples to 8.10 μm (1234 cm−1) in the Ca-richest sample. Combining the CF position and the autocorrelation-derived value allowed to determine the degree of Al,Si order of the samples based on reflection spectra. The wavelength of the Transparency feature (TF) in the finest analyzed grain size fraction also depends on the chemical composition and the degree of Al,Si order. Our results are helpful for the interpretation of data returned by the MERTIS experiment onboard BepiColombo. The data help to distinguish between space weathering, shock effects, and ordering effects in plagioclase samples.

¹Zachary A. Torrano,^1,2Jemma Davidson,¹Meenakshi Wadhwa
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13587]
¹School of Earth and Space Exploration, Arizona State University, Tempe, Arizona, 85287 USA
²Center for Meteorite Studies, Arizona State University, Tempe, Arizona, 85287 USA
Published by arrangement with John Wiley & Sons

The similarities between CV and CK chondrites are so substantial that some studies have argued for a common parent body origin. These similarities also mean that they are susceptible to misclassification as one another. It is, therefore, important to accurately classify CV and CK chondrites to properly compare the properties of the two groups and evaluate the single parent body hypothesis. In this study, we re‐evaluate the current classification of Northwest Africa (NWA) 2900 as a CV3 chondrite. Based on chondrule abundance (~13%), average chondrule diameter (1.11 ± 0.67 mm), iron content in chondrule olivine (Fa1 to Fa35 with a peak near ~Fa31) and matrix olivine (Fa33 to Fa36), magnetite abundance (~4 vol%), elemental abundances in olivine (Cr2O3, Al2O3, TiO2, MnO, NiO, and CaO) and magnetite (Cr2O3, Al2O3, TiO2, and NiO), and comparison with previously reported data for CV and CK chondrites, we propose that the classification of NWA 2900 be changed from CV3 chondrite to CK3 chondrite, with characteristics most similar to those of the CK3.8 subtype. We additionally suggest minor modifications to the compositional criteria used to distinguish between CV and CK chondrites and demonstrate that NWA 2900 extends the range of bulk oxygen isotope compositions of CK chondrites.