Paolo A. Sossi¹, Anat Shahar²
Elements – Link to Article [https://doi.org/10.2138/gselements.17.6.407]
¹ETH Zürich, Institute of Geochemistry and Petrology, Zürich, CH-8092, Switzerland
²Carnegie Institution for Science, Earth and Planets Laboratory, Washington, DC, 20015-1305, USA
Copyright Elsevier

Evaporation of magma oceans exposed to space may have played a role in the chemical and isotopic compositions of rocky planets in our Solar System (e.g., Earth, Moon, Mars) and their protoplanetary antecedents. Chemical depletion of moderately volatile elements and the enrichment of these elements’ heavier isotopes in the Moon and Vesta relative to chondrites are clear examples. Evaporation is also thought to be an important process in some exoplanetary systems. Identification of evaporation signatures among the rock-forming elements could elucidate important reactions between melts and vapors during planet formation in general, but the process is more complicated than is often assumed.

Haolan Tang, Edward D. Young
Elements – Link to Article [https://doi.org/10.2138/gselements.17.6.401]
University of California, Los Angeles Department of Earth, Planetary, and Space Sciences, 595 Charles E. Young Dr. East, Los Angeles, CA, 90095, USA
Copyright Elsevier

Evaporation of magma oceans exposed to space may have played a role in the chemical and isotopic compositions of rocky planets in our Solar System (e.g., Earth, Moon, Mars) and their protoplanetary antecedents. Chemical depletion of moderately volatile elements and the enrichment of these elements’ heavier isotopes in the Moon and Vesta relative to chondrites are clear examples. Evaporation is also thought to be an important process in some exoplanetary systems. Identification of evaporation signatures among the rock-forming elements could elucidate important reactions between melts and vapors during planet formation in general, but the process is more complicated than is often assumed.

Christoph Burkhardt
Elements – Link to Article [https://doi.org/10.2138/gselements.17.6.395]
University of Münster, Institut für Planetologie, Wilhelm-Klemm-Straße 10, D-48149 Münster, Germany
Copyright Elsevier

The detection of exoplanets and accretion disks around newborn stars has spawned new ideas and models of how our Solar System formed and evolved. Meteorites as probes of geologic deep time can provide ground truth to these models. In particular, stable isotope anomalies in meteorites have recently emerged as key tracers of material flow in the early Solar System, allowing cosmochemists to establish a “planetary isotopic genealogy”. Although not complete, this concept has substantially advanced our understanding of Solar System evolution, from the collapse of the Sun’s parental molecular cloud to the accretion of the planets.

Marianna Marchini¹, Massimo Gandolfi¹, Lucia Maini¹, Lucia Raggetti², and Matteo Martelli²
Proceedings of the National Academy of Science of the USA (PNAS) 119 (14) e2119194119 Link to Article [https://doi.org/10.1073/pnas.2123171119]
¹Department of Chemistry “Giacomo Ciamician”, University of Bologna, 40126, Bologna, Italy
²Department of Philosophy and Communication Studies, University of Bologna, 40126, Bologna, Italy

Sulfate aerosols have long been implicated as a primary forcing agent of climate change and mass extinction in the aftermath of the end-Cretaceous Chicxulub bolide impact. However, uncertainty remains regarding the quantity, residence time, and degree to which impact-derived sulfur transited the This paper explores the chemistry of mercury as described in ancient alchemical literature. Alchemy’s focus on the knowledge and manipulation of natural substances is not so different from modern chemistry’s purposes. The great divide between the two is marked by the way of conceptualizing and recording their practices. Our interdisciplinary research group, composed of chemists and historians of science, has set off to explore the cold and hot extraction of mercury from cinnabar. The ancient written records have been perused in order to devise laboratory experiments that could shed light on the material reality behind the alchemical narratives and interpret textual details in a unique perspective. In this way, it became possible to translate the technical lore of ancient alchemy into the modern language of chemistry. Thanks to the replication of alchemical practices, chemistry can regain its centuries-long history that has fallen into oblivion.

S. N. Ferguson, A. R. Rhoden, M. R. Kirchoff
Journal of Geophysical Research (Planets) (in Press) Link to Article [https://doi.org/10.1029/2022JE007204]
Soutwest Research Institute Boulder, CO, USA
Published by arrangement with John Wiley & Sons

Recent dynamical modeling of the formation and evolution of the Saturnian satellites suggests that the ages of the mid-sized inner moons (Mimas, Enceladus, Tethys, Dione, and Rhea) could be as young as 100 Myr. This estimate is in contrast to most previous modeling and observational work that suggest an age more contemporaneous with the formation of Saturn 4.5 Ga ago. Given the heritage of using craters to constrain surface ages, we examine the impact craters of Dione using imagery from NASA’s Cassini ISS camera and analyze their size-frequency distributions (SFDs) to understand impactor populations. We survey four areas across different geologic terrains and compare our crater counts to standard outer solar system production functions. In addition to crater counts, we study several crater types such as elliptical and polygonal to further examine the bombardment source for the craters. We find evidence for a Saturn-specific planetocentric impactor source, as none of the standard production functions fit the data. We compare our Dione data with our work on Tethys and find similarly shaped SFDs between the satellites. However, Dione’s surface has been extensively modified to remove smaller craters (D ∼< 5km) and has been bombarded by larger impactors, creating more D ∼> 20 km on Dione than Tethys. In contrast, Tethys more generally represents an ancient unmodified surface within the Saturn system. More complete observations and assessment of the cratering records on the satellites of Uranus and Neptune’s moon Triton would enable better constraints on the bombardment history of the Saturn system.

Cauê S. Borlina¹, Benjamin P. Weiss¹, James F. J. Bryson³, Philip J. Armitage^3,4
Journal of Geophysical Research (Planets) (in Press) Link to Article [https://doi.org/10.1029/2021JE007139]
¹Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
²Department of Earth Sciences, Oxford University, Oxford, UK
³Center for Computational Astrophysics, Flatiron Institute, 162 Fifth Avenue, New York, NY,USA
⁴Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, USA
Published by arrangement with John Wiley & Sons

The evolution and lifetime of protoplanetary disks (PPDs) play a central role in the formation and architecture of planetary systems. Astronomical observations suggest that PPDs evolve in two timescales, accreting onto the star for up to several million years (Myr) followed by gas-dissipation within ≲1 Myr. Because solar nebula magnetic fields are sustained by the gas of the protoplanetary disk, we can use paleomagnetic measurements to infer the lifetime of the solar nebula. Here we use paleomagnetic measurements of meteorites to constrain this lifetime and investigate whether the solar nebula had a two-timescale evolution. We report on paleomagnetic measurements of bulk subsamples of two CO carbonaceous chondrites: Allan Hills A77307 and Dominion Range 08006. If magnetite in these meteorites can acquire a crystallization remanent magnetization that recorded the ambient field during aqueous alteration, our measurements suggest that the local magnetic field strength at the CO parent-body location was <0.9 µT at some time between 2.7-5.1 Myr after the formation of calcium-aluminum-rich inclusions. Coupled with previous paleomagnetic studies, we conclude that the dissipation of the solar nebula in the 3-7 AU region occurred <1.5 Myr after the dissipation of the nebula in the 1-3 AU region, suggesting that protoplanetary disks go through a two-timescale evolution in their lifetime consistent with dissipation by photoevaporation and/or magnetohydrodynamic winds. We also discuss future directions necessary to obtain robust records of solar nebula fields using bulk chondrites, including obtaining ages from meteorites and experimental work to determine how magnetite acquires magnetization during chondrite parent-body alteration.

Saverio Cambioni¹, Katherine de Kleer², Michael Shepard³
Journal of Geophysical Research (Planets) (in Press) Link to Article [https://doi.org/10.1029/2021JE007091]
¹Department of Planetology, Kobe University, Kobe, Department of Earth, Atmospheric & Planetary Sciences, Massachusetts Institute of Technology, 3Cambridge, MA, USA
²Division of Geological & Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
³Department of Environmental, Geographical & Geological Sciences, Bloomsburg University, Bloomsburg, PA, USA
Published by arrangement with John Wiley & Sons

Main-belt asteroid (16) Psyche is the largest M-type asteroid, a class of object classically thought to be the metal cores of differentiated planetesimals and the parent bodies of the iron meteorites. de Kleer, Cambioni, and Shepard (2021) presented new data from the Atacama Large Millimiter Array (ALMA), from which they derived a global best-fit thermal inertia and dielectric constant for Psyche, proxies for regolith particle size, porosity, and/or metal content, and observed thermal anomalies that could not be explained by surface albedo variations only. Motivated by this, here we fit a model to the same ALMA dataset that allows dielectric constant and thermal inertia to vary across the surface. We find that Psyche has a heterogeneous surface in both dielectric constant and thermal inertia but, intriguingly, we do not observe a direct correlation between these two properties over the surface. We explain the heterogeneity in dielectric constant as being due to variations in the relative abundance of metal and silicates. Furthermore, we observe that the lowlands of a large depression in Psyche’s shape have distinctly lower thermal inertia than the surrounding highlands. We propose that the latter could be explained by a thin mantle of fine regolith, fractured bedrock, and/or implanted silicate-rich materials covering an otherwise metal-rich surface. All these scenarios are indicative of a collisionally evolved world.

Chavan, A., Bhore, V., Bhandari, S.
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2022.115118]
Department of Earth and Environmental Science, K.S.K.V. Kachchh University, Bhuj 370001, India
Copyright Elsevier

Martian geology and surface geomorphic features are grouped under Noachian, Hesperian, and Amazonian eras, based on the crater retention ages and resurfacing ages by crater densities. Comparing the similarities and differences between Martian landforms and their terrestrial analogues promotes an understanding of how surface processes operated on both planets. The study focusses on the processes responsible for the evolution of fluvial valleys flanking volcanic channels and the fluvial terraces with an objective towards ascertaining the role of changing climate, tectonic, and volcanic conditions. We have studied the channels that developed on the flank of volcanic crater Ceraunius Tholus and compared with the monogenetic volcanic field of Dhinodhar Hill which have been significantly modified by fluvial processes. Similarly, the fluvial basins developed on the Hesperian volcanic units of Euhus plateau were compared with the Alaldari drainage of Upper Tapi river basin, showing the development of theater-headed channels and valleys, and relative fluvial features showing the strong influence of catastrophic climate and tectonic, which is also supported by the morphometric analysis in modulating the topography. The fluvial terraces developed in the Nubra and Shyok rivers of Ladakh and Upper and Middle reaches of Sutlej in Central Himalayas are compared with Noctis fossae on Mars both developed due to the interplay of tectonism and climate.

¹Ashley R.Clendenen,²Aleksandr Aleksandrov,^2,3Brant M.Jones,⁴Peter G.Loutzenhiser,⁵Daniel T.Britt,^1,2,3Thomas M.Orlando
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.epsl.2022.117632]
¹School of Physics, Georgia Institute of Technology, Atlanta, 30332-0405, GA, USA
²School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, 30332-0405, GA, USA
³Center for Space Technology and Research, Georgia Institute of Technology, Atlanta, 30332-0405, GA, USA
⁴George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, 30332-0405, GA, USA
⁵Department of Physics, The University of Central Florida, Orlando, FL 32816, USA
Copyright Elsevier

Water and molecular hydrogen evolution from Apollo sample 14163 and lunar regolith simulants LMS-1, a mare simulant, and LHS-1, a highlands simulant, were examined using Temperature Programmed Desorption (TPD) in ultra-high vacuum. LMS-1, LHS-1, and Apollo 14163 released water upon heating, whereas only the Apollo sample directly released measurable quantities of molecular hydrogen. The resulting H2O and H2 TPD curves were fit using a model which considers desorption at the vacuum grain interface, transport in the void space between grain-grain boundaries, molecule formation via recombination reactions and sub-surface diffusion. The model yielded a most probable H2O formation and desorption effective activation energy of ∼150 kJ mol−1 for all samples. The probability distribution widths of the effective activation energies were ∼100–400, ∼100–350, and ∼100–300 kJ mol−1 for LMS-1, LHS-1, and Apollo 14163, respectively. In addition to having the narrowest energy distribution width, the Apollo sample released the least amount to water (103 ppm) relative to LMS-1 (176 ppm) and LHS-1 (195 ppm). Since essentially no molecular hydrogen was observed from the simulants, the results indicate that LMS-1 and LHS-1 display water surface formation, binding, and transport interactions similar to actual regolith but not the desorption chemistry associated with the implanted hydrogen from the solar wind. Overall, these terrestrial surrogates are useful for understanding the surface and interface interactions of lunar regolith grains, which are largely dominated by the terminal hydroxyl sites under both solar wind bombardment and terrestrial preparation conditions.

^1,2Alan E.Rubin,¹Bidong Zhang,³Nancy L.Chabot
Geochmica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.05.020]
¹Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, CA 90095-1567, USA
²Maine Mineral & Gem Museum, 99 Main Street, P.O. Box 500, Bethel, ME 04217, USA
³Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA
Copyright Elsevier

Although IVA irons have O- and Cr-isotopic compositions resembling those of equilibrated LL chondrites, the bulk composition of refractory elements (e.g., Re, Ir, Pt) in the IVA core appears to be significantly lower than LL. These compositional discrepancies suggest known IVA irons may be missing early crystallized samples. We hypothesize the bulk composition of the IVA core is LL-like, but current collections do not include early fractional-crystallization IVA products. Our fractional-crystallization modeling of element vs. Au trends suggests that extant IVA irons are products of >40% crystallization of the core, assuming an initial 2.9 wt.% S content. The model-derived bulk (Ni-normalized) composition of the IVA core is depleted relative to LL in most moderate volatiles: S (82% depletion), Ge (99.9% depletion), Ga (95% depletion), As (50% depletion); however, Au is enriched by 10%. Because moderate volatiles with depletions >80% relative to LL have 50%-condensation temperatures <1020 K, it seems likely these depletions reflect post-accretion impact-induced volatilization of the IVA asteroid. The mean Ni-normalized compositions of analyzed IVA irons yield a lesser depletion of As (30%) and greater enrichment of Au (48%) relative to LL. The IVA asteroid may have experienced a complex parent-body thermal and collisional history: (1) differentiation, (2) impact-induced mantle stripping, devolatilization, and fractional condensation, (3) rapid crystallization of the core from the outside inwards, (4) shattering of the core after ∼75% crystallization, (5) quenching of thinly insulated samples (e.g., Fuzzy Creek), (6) formation of amorphous free silica in several IVA irons after impact-induced vaporization of portions of the overlying silicate mantle, followed by fractional condensation, (7) loss of portions of the core representing the first 40% of crystallization, (8) reaccretion of some core fragments, facilitating relatively slow cooling of a few IVA irons (e.g., Duchesne, Duel Hill (1854), Chinautla), and (9) collisional resetting of the Re-Os clock 4456±25 Ma ago.