astronomy

NWA 11562: A Unique Ureilite with Extreme Mg-rich Constituents

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1,2Mingbao Li,3,4Ke Zhu,1,5Yan Fan,6P. M. Ranjith,7Chao Wang,1Wen Yu, 1,8,9Shijie Li
The Planetary Science Journal 5, 178 Open Access Link to Article [DOI 10.3847/PSJ/ad6154]
1Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 55021, People’s Republic of China
2State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Macau 999078, People’s Republic of China
3Freie Universität Berlin, Institut für Geologische Wissenschaften, Malteserstr. 74-100, Berlin 12249, Germany
4Bristol Isotope Group, School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen’s Road, Bristol BS8 1RJ, UK
5State Key Laboratory of Continental Dynamics and Department of Geology, Northwest University, Xi’an 710069, People’s Republic of China
6Graduate School of Advanced Science and Technology, Japan Advanced Institute of Science and Technology (JAIST), 1-1 Asahidai, Nomi, Ishikawa, 923-1292, Japan
7School of Earth and Space Sciences, Peking University, Beijing 100871, People’s Republic of China
8CAS Center for Excellence in Comparative Planetology, Hefei, 230022, People’s Republic of China

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Low temperature phase transitions in the visible and near-infrared (VNIR) reflectance spectra of (NH4)2HPO4 and (NH4)HSO4 salts

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1M. Fastelli, 2B. Schmitt, 2P. Beck, 2O. Poch, 1A. Zucchini, 1P. Comodi
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2024.116321]
1Department of Physics and Geology, University of Perugia, I-06123 Perugia, Italy
2Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
Copyright Elsevier

The detection of ammonium bearing crystalline solids in salt-water systems on icy bodies and solar system bodies could provide information about the ascent of these salts from a deep reservoir within the hydrosphere. Due to their chemical-physical properties, NH4+ compounds play a key role both in the internal dynamics of celestial bodies and in the potential habitability of ocean worlds.. In this work we analysed the reflectance spectra of two synthetic NH4+ salts: ammonium hydrogen phosphate (NH4)2HPO4 and ammonium hydrogen sulphate (NH4)HSO4 in the 1–4.2 μm spectral range at low temperature, between 110 and 290 K. For (NH4)2HPO4 we also examined the effect of three different grain sizes (150–125 μm; 125–80 μm; 80–32 μm). The collected reflectance spectra show absorption features related to NH4+ group overtone and combination modes in the 1–2.5 μm range. In particular, the bands located at ~1.09 μm (3ν3), ~1.30 μm (2ν3 + ν4), ~1.58 μm (2ν3), ~2.02 μm (ν2 + v3) and ~ 2.2 μm (v3 + v4) could be useful to discriminate these salts. The low temperature spectra, compared to those at ambient temperature, reveal finer structures, displaying sharper and narrower absorption bands. The selected NH4+-bearing salts are subjected to reversible low temperature phase transitions, which are revealed in the spectra by a progressive growth and shift of the bands toward shorter wavelengths with a drastic change of their depth. We performed laboratory measurements ammonium (NH4+) compounds to address the limited data available expanding the existing database. The collected cryogenic spectra can be directly compared with remote sensing data from planetary missions of the upcoming decade such as NASA’s Europa Clipper, and ESA’s JUICE and the newly launched James Webb Space Telescope expanding the existing database of ammonium compounds at cryogenic temperature.

Rb-Sr constraints on the age of Moon formation

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Elsa Yobregat, Caroline Fitoussi, Bernard Bourdon
Icarus (in Press) Open Access
Link to Article [https://doi.org/10.1016/j.icarus.2024.116164]
Laboratoire de Géologie de Lyon, ENS Lyon, CNRS, UCBL, France

Determining the age of the Moon, which is commonly considered as the termination of Earth accretion has been a complex challenge for geochronology. A number of methods have been used to delineate the age of the Moon based either on absolute chronology of lunar rocks or have relied on more indirect methods using short-lived nuclides such as 182Hf that was present in the early history of the Solar System. Model ages usually require some assumptions that are sometimes controversial or harder to verify.

In this study, new high precision Sr isotope data (2.4 ppm, 2SD) were obtained for a well-dated lunar anorthosite (60025) in order to better constrain the initial 87Sr/86Sr of the bulk silicate Moon. This new data is then used to model the Sr isotope evolution of the Earth-Moon starting from the beginning of the Solar System. To comply with the Hfsingle bondW and stable isotope constraints, we then assume that the Earth and Moon were equilibrated at the time of Moon formation. By investigating systematically all the sources of uncertainties in our model, we show that compared with previous work on anorthosite, one can tighten the constraints on the youngest age of Moon formation to no >79 Ma after the beginning of the Solar System, i.e. the Moon cannot be younger than 4488 Ma.

In Memoriam: Burkhard Dressler (1939–2024)

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Wolfram Dressler1 , Wolf Uwe Reimold 2,
Virgil L. (Buck) Sharpton3 and Christian Koeberl4
Meteoritics & Planetary Science (in Press) Open Access
Link to Article [https://doi.org/10.1111/maps.14218]
1Geography, Earth and Atmospheric Sciences, The University of Melbourne, Melbourne, Victoria,
Australia
2Institute of Geoscience, University of Brasilia, Brasilia, Brazil
312515 Mount Bross Place, Peyton, Colorado, 80831, USA
4Department of Lithospheric Research, University of Vienna, Vienna, Austria

Sound velocities in lunar mantle aggregates at simultaneous high pressures and temperatures: Implications for the presence of garnet in the deep lunar interior

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Marisa C. Wood1, Steeve Gréaux1, Yoshio Kono1, Sho Kakizaw1,2, Yuta Ishikawa1, Sayako Inoué1, Hideharu Kuwahara1, Yuji Higo2, Noriyoshi Tsujino2, Tetsuo Irifune1
Earth and Planetary Science Letters 641, 118792
Link to Article [https://doi.org/10.1016/j.epsl.2024.118792]
1Geodynamics Research Center, Ehime University, Matsuyama, Japan
2Japan Synchrotron Radiation Research Institute, SPring-8, Hyogo, Japan
Copyright Elsevier

Recent experimental and theoretical studies on lunar magma ocean crystallisation have suggested the presence of significant proportions of garnet in the deep lunar interior. While phase relation studies indicate a deep lunar mantle consisting of olivine, pyroxene, and garnet, the compatibility of such an assemblage with seismic models of the lunar interior is yet untested. In this study we report compressional and shear wave velocities in an iron-rich assemblage consisting of olivine, orthopyroxene, clinopyroxene, and garnet up to ∼8 GPa and 1300 K, by means of ultrasonic interferometry measurements combined with synchrotron techniques using the multi-anvil press apparatus. Sound velocity and density models of lunar mantle rocks along a selenotherm based on our experimental results find good agreement with the seismic and density profiles at lunar interior depths of 740–1260 km. Further models are constructed, allowing for the variation of chemical composition, phase proportion, and temperature; these suggest that a garnet-rich deep lunar mantle is compatible with present-day lower lunar mantle temperatures of between 1400–1800 K. Our results show that lunar mantle rocks with up to 33 wt.% garnet may provide an explanation for the observed high velocities of the lower lunar mantle. The presence of garnet in the lowermost part of the Moon’s mantle has significant implications for the depth and temperature of the Moon’s magma ocean as well as the composition, structure and internal dynamics of the solid Moon.

Accretion of warm chondrules in weakly metamorphosed ordinary chondrites and their subsequent reprocessing

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aAlex M. Ruzicka, aRichard C. Hugo, b,cJon M. Friedrich, aMichael T. Ream
Geochimica et Cosmochimica Acta (in Press)
Link to Article [https://doi.org/10.1016/j.gca.2024.05.031]
aCascadia Meteorite Laboratory, Department of Geology, Portland State University, 1721 SW Broadway, Portland, OR 97207, USA
bDepartment of Chemistry, Fordham University, Bronx, NY 10458, USA
cDepartment of Earth and Planetary Science, American Museum of Natural History, New York, NY 10024, USA
Copyright Elsevier

To better understand chondrite accretion and subsequent processes, the textures, crystallography, deformation, and compositions of some chondrite constituents in ten lithologies of different cluster texture strength were studied in seven weakly metamorphosed (Type 3) and variably shocked ordinary chondrites (Ragland—LL3 S1, Tieschitz—H/L3 S1, NWA 5421—LL3 S2, NWA 5205—LL3 S2, NWA 11905—LL3-5 S3, NWA 5781—LL3 S3, NWA 11351—LL3-6 S4) using optical and electron microscopy and microtomography techniques.

Results support a four-stage model for chondrite formation. This includes 1) limited annealing following collisions during chondrule crystallization and rapid cooling in space prior to accretion, as evidenced by olivine microstructures consistent with dislocation recovery and diffusion; 2) initial accretion of still-warm chondrules into aggregates at an effective chondrite accretion temperature of ∼900-950 °C with nearly in situ impingement deformation between adjacent chondrules in strongly clustered lithologies (NWA 5781, Tieschitz, NWA 5421, NWA 5205 Lithology A), as evidenced by intragranular lattice distortions in olivine consistent with high-temperature slip systems, and by evidence that some olivine-rich objects in Tieschitz accreted while partly molten; 3) syn- or post-accretion bleaching of chondrule mesostases, which transferred feldspathic chondrule mesostasis to an interchondrule glass deposit found in strongly clustered lithologies, as evidenced by chemical data and textures; and 4) post-bleaching weak or strong shocks that resulted in destruction of interchondrule glass and some combination of brecciation, foliation of metal and sulfide, and melting and shock-overprinting effects, as evidenced by poor cluster textures and presence of clastic texture, alignment of metal and sulfide grains caused by shock compression, presence of impact-generated glass, and changes in olivine slip systems. The data support the model of Metzler (2012), who suggested that chondrules in ordinary chondrites accreted while still warm to form cluster chondrite textures as a “primary accretionary rock” (our Stage 2), and that subsequent brecciation destroyed this texture to create chondrites with weak cluster texture (our Stage 4).