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.