^1,2Neveu, M.,³Vernazza, P.
Astronophysical Journal 875, 30 Link to Article [DOI: 10.3847/1538-4357/ab0d87]
¹University of Maryland, 4296 Stadium Dr., College Park, MD 20742, United States
²NASA Goddard Space Flight Center, 8800 Greenbelt Rd., Greenbelt, MD 20770, United States
³Aix-Marseille Universite, CNRS, Laboratoire d’Astrophysique de Marseille, 38 Rue Frederic Joliot Curie, Marseille, F-13013, France

The parent bodies of ordinary chondrites, carbonaceous CM chondrites, and interplanetary dust particles (IDPs) represent most of the mass of the solar system’s small (D ≤ 250 km) bodies. The times of formation of the ordinary and carbonaceous CM chondrite parent bodies have previously been pinpointed, respectively, to ≈2 and 3–4 million years after calcium–aluminum-rich inclusions (CAIs). However, the timing of the formation of IDP parent bodies such as P- and D-type main-belt asteroids and Jupiter Trojans has not been tightly constrained. Here, we show that they formed later than 5–6 million years after CAIs. We use models of their thermal and structural evolution to show that their anhydrous surface composition would otherwise have been lost due to melting and ice-rock differentiation driven by heating from the short-lived radionuclide ²⁶Al. This suggests that IDP-like volatile-rich small bodies may have formed after the gas of the protoplanetary disk dissipated and thus later than the massive cores of the giant planets. It also confirms an intuitive increase in formation times with increased heliocentric distance, and suggests that there may have been a gap in time between the formation of carbonaceous chondrite (chondrule-rich) and IDP (chondrule-poor) parent bodies.

^1,2Guitreau, M.,³Flahaut, J.
Nature Communications 10, 2457 Link to Article [DOI: 10.1038/s41467-019-10382-y]
¹School of Earth and Environmental Sciences, University of Manchester, Oxford road, Manchester, M13 9PL, United Kingdom
²Université Clermont Auvergne, Laboratoire Magmas et Volcans, 6 avenue Blaise Pascal, Aubière, 63178, France
³CRPG, CNRS/Université de Lorraine, Vandœuvre-lès-Nancy, 54500, France

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^1,2Smith, K.E.,²House, C.H.,³Arevalo, R.D., Jr.,^4,5Dworkin, J.P.,^1,4,5Callahan, M.P.
Nature Communications 10, 2777 Link to Article [DOI: 10.1038/s41467-019-10866-x]
¹Department of Chemistry and Biochemistry, Boise State University, Boise, ID 83725, United States
²Department of Geosciences and Penn State Astrobiology Research Center, Pennsylvania State University, University Park, PA 16801, United States
³Department of Geology, University of Maryland, College Park, MD 20742, United States
⁴Goddard Center for Astrobiology, NASA Goddard Space Flight Center, Greenbelt, MD 20771, United States
⁵Astrochemistry Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771, United States

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^1,2Maxwell M. Thiemens,^1,3Peter Sprung,¹Raúl O. C. Fonseca,^4,5Felipe P. Leitzke,¹Carsten Münker
Nature Geoscience (in Press) Link to Article [https://doi.org/10.1038/s41561-019-0398-3]
^{1Institut für Geologie und Mineralogie, Universität zu Köln, Köln, Germany
2Laboratoire G-Time, Département Géosciences, Environnement et Société, Université Libre de Bruxelles, Brussels, Belgium
3Hot Laboratory Division (AHL), Paul Scherrer Institut, Villigen, Switzerland
4Steinmann Institut, Universität Bonn, Bonn, Germany
5Isotope Geology Laboratory, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil}

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¹Aaron J. Cavosie,^2,3Christian Koeberl
Geology 47, 609-612. Link to Journal [https://doi.org/10.1130/G45974.1]
¹Space Science and Technology Centre and The Institute for Geoscience Research, School of Earth and Planetary Science, Curtin University, Perth, Western Australia 6102, Australia
²Natural History Museum, Burgring 7, A-1010 Vienna, Austria
³Department of Lithospheric Research, University of Vienna, Althanstrase 14, A-1090 Vienna, Austria

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^1,2Qian Ma,^2,3Ming Yang,^2,3Han Zhao,⁴Noreen J. Evans,^2,3Zhu-Yin Chu,^2,3Lie-Wen Xie,^2,3Chao Huang,¹Zhi-Dan Zhao,^2,3Yue-Heng Yang
Journal of Analytical Atomic Spectroscopy 34, 1256-1262 Link to Article [DOI:
10.1039/C9JA00034H]
¹State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Science and Resources, China University of Geosciences, Beijing, P. R. China
²State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, P. R. China
³University of Chinese Academy of Sciences, Beijing, P. R. China
⁴School of Earth and Planetary Science, John de Laeter Centre, Curtin University, Australia

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^1,2Fang, T.,^1,3Liu, Y.
Acta Geochimica 38, 469-471 Link to Article [DOI: 10.1007/s11631-019-00344-y]
¹State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, China
²University of Chinese Academy of Sciences, No. 19(A) Yuquan Road, Shijingshan District, Beijing, 100049, China
³CAS Center for Excellence in Comparative Planetology, Hefei, China

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^1,2Joshua F.Snape,³Alexander A.Nemchin,¹Martin J.Whitehouse,¹Renaud E.Merle, ⁴Thomas Hopkinson,^4,5Mahesh Anand
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2019.07.042]
¹Department of Geosciences, Swedish Museum of Natural History, SE-104 05 Stockholm, Sweden
²Faculty of Earth and Life Sciences, VU Amsterdam, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands
³Department of Applied Geology, Curtin University, Perth, WA 6845, Australia
⁴School of Physical Science, The Open University, Milton Keynes, MK7 6AA
⁵Department of Earth Sciences, The Natural History Museum, London, SW7 5BD
Copyright Elsevier

Precise crystallisation ages have been determined for a range of Apollo basalts from Pb-Pb isochrons generated using Secondary Ion Mass Spectrometry (SIMS) analyses of multiple accessory phases including K-feldspar, K-rich glass and phosphates. The samples analysed in this study include five Apollo 11 high-Ti basalts, one Apollo 14 high-Al basalt, seven Apollo 15 low-Ti basalts, and five Apollo 17 high-Ti basalts. Together with the samples analysed in two previous similar studies, Pb-Pb isochron ages have been determined for all of the major basaltic suites sampled during the Apollo missions. The accuracy of these ages has been assessed as part of a thorough review of existing age determinations for Apollo basalts, which reveals a good agreement with previous studies of the same samples, as well as with average ages that have been calculated for the emplacement of the different basaltic suites at the Apollo landing sites. Furthermore, the precision of the new age determinations helps to resolve distinctions between the ages of different basaltic suites in more detail than was previously possible. The proposed ages for the basaltic surface flows at the Apollo landing sites have been reviewed in light of these new sample ages. Finally, the data presented here have also been used to constrain the initial Pb isotopic compositions of the mare basalts, which indicate a significant degree of heterogeneity in the lunar mantle source regions, even among the basalts collected at individual landing sites.

^1,2Lisé-Pronovost, A. et al. (>10)
Scientific Drilling 25, 1-14 Link to Article [DOI: 10.5194/sd-25-1-2019]
¹School of Earth Sciences, University of Melbourne, Melbourne, Australia
²The Australian Archaeomagnetism Laboratory, Department of Archaeology and History, La Trobe University, Melbourne Campus, Bundoora, VIC 3086, Australia

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¹Lars E.Borg,¹Amy M.Gaffney,¹Thomas S.Kruijer,¹Naomi A.Marks,¹Corliss K.Sio,¹Josh Wimpenny
Earth and Planetary Science Letters 523, 115706 Link to Article [https://doi.org/10.1016/j.epsl.2019.07.008]
¹Nuclear and Chemical Sciences Division, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
Copyright Elsevier

Mare basalt sources and ferroan anorthosite suite cumulates define a linear array on a ¹⁴⁶Sm/¹⁴⁴Nd versus ¹⁴²Nd/¹⁴⁴Nd isochron plot demonstrating these materials were derived from a common reservoir at 4336⁺³¹/₋₃₂ Ma. The minimum proportion of the Moon that was in isotopic equilibrium at this time is estimated to be 1-3% of its entire volume based on the geographic extent from which the analyzed samples were collected and the calculated depths from which the samples were derived. Scenarios in which large portions of the Moon were molten to depths of many hundreds of kilometers are required to produce the observed Sm-Nd isotopic equilibrium between the mantle and crustal rocks at 4.34 Ga. This is a consequence of the fact that limited heating of a solid Moon above the blocking temperature of the Sm-Nd isotopic system is insufficient to diffusively homogenize radiogenic Nd throughout the mantle and crust. There are three scenarios that might account for global-scale isotopic equilibrium on the Moon relatively late in Solar System history including: (1) Sm-Nd re-equilibration of a solid Moon resulting from widespread melting in response to mantle overturn or a very large impact, (2) early accretion of the Moon followed by delayed cooling due to the presence of an additional heat source that kept a large portion of the Moon molten until 4.34 Ga, or (3) late accretion of the Moon followed by rapid cooling of the magma ocean late in Solar System history. Neither density-driven overturn of the mantle, nor a large impact, are likely to homogenize the mantle and crust to the extent required by the Sm-Nd isochron. Likewise, secondary heating mechanisms, such as tidal heating or radioactive decay, are not efficient enough to keep the Moon molten to the depth of the mare basalt source regions for many tens to hundreds of millions of years. Instead, the age of equilibrium between such a compositionally diverse set of rocks, produced on a global scale, likely records the time of primordial solidification of the Moon from a magma ocean. This scenario accounts for both the petrogenetic characteristics of lunar rock suites, as well as their Sm-Nd isotopic systematics. It is supported by the preponderance of ∼4.35 Ga ages obtained for other hypothetical magma ocean crystallization products, such as ferroan anorthosite suite rocks and K, REE, and P enriched cumulates that are thought to represent flotation cumulates of the magma ocean and the last vestiges of magma ocean solidification, respectively.