¹Lowry, Vanessa C.,¹V.C.Donaldson Hanna, Kerri L.,¹Campins, Humberto,²Bowles, Neil,³Hamilton, Victoria E.,²Brown, Eloïse C.
Earth and Space Science 9, e2021EA002146 Link to Article [DOI
10.1029/2021EA002146]
¹University of Central Florida, Orlando, FL, United States
²University of Oxford, Oxford, United Kingdom
³Southwest Research Institute, Boulder, CO, United States

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^1,2S. Sarkar,³H. Moitra,^1,3S. Bhattacharya,¹A. Dagar,⁴D. Ray,³S. Gupta,³A. Chavan,⁴A. D. Shukla,²S. Bhandari
Journal of Geophysical Research (Planets)(in Press) Link to Article [https://doi.org/10.1029/2022JE007299]
¹Space Applications Centre, Indian Space Research Organisation, Ahmedabad, 380015 Gujarat, India
²Department of Earth and Environment Science, Krantiguru Shyamji Krishna Verma Kachchh University, Bhuj, 370001 Gujarat, India
³Department of Geology and Geophysics, Indian Institute of Technology Kharagpur, Kharagpur, 721302 India
⁴Physical Research Laboratory, Ahmedabad, 380 009 Gujarat, India
Published by arrangement with John Wiley & Sons

Hot spring localities on continents may represent the most probable locales for the formation of early life constituents on Earth. Apart from liquid water and carbohydrates, these components also include elements like boron that are crucial for stabilization of the complex organic molecules that constitute life. Many of these life sustaining ingredients are commonly found in the vicinity of terrestrial hot springs. Analogously, similar existing or extinct hot spring localities on other planets may constitute prospective astrobiological sites. In the present study, we have characterized the complete mineralogical assemblage of the Puga hot spring deposit, Ladakh, India, using detailed spectroscopic and X-ray diffraction studies. The spectroscopic characterization was done using both field as well as lab based visible/near-infrared (VNIR; 400-2500 nm) and lab measured mid-infrared (MIR, 4000-400 cm-1) hyperspectral data. The identified mineral phases include Na-borates, such as borax and tincalconite, and hydrous sulfates such as jarosite, alunite, copiapite, tamarugite and gypsum, in conjunction with native sulfur, halite and opaline silica. Borate minerals have been identified from the valley-fill material along with halite and opaline silica, whereas sulfates occur alongside crystalline sulfur deposits. We have compared mineral assemblages found in Puga with other hot spring/hydrothermal deposits on Earth identified as martian analog sites, and also with mineral assemblages identified in situ on Mars. We argue that the spectral characterization of hydrated borates in natural association with hydrous sulfates can be used for identification of fossil/paleo hydrothermal settings on Mars that are prospective in the search for extinct/extant extra-terrestrial life.

¹S. Czarnecki,¹C. Hardgrove,²R. E. Arvidson,²M. N. Hughes,³M. E. Schmidt,³T. Henley,⁴L. M. Martinez Sierra,⁴I. Jun,⁵M. Litvak,⁵I. Mitrofanov
Journal of Geophysical (Planets)(in Press) Link to Article [https://doi.org/10.1029/2021JE007104]
¹School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA
²Department of Earth and Planetary Sciences, Washington University in St. Louis, St. Louis, MO, USA
³Department of Earth Sciences, Brock University, St. Catharines, ON, Canada
⁴Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
⁵Space Research Institute, Russian Academy of Sciences, Moscow, Russia
Published by arrangement with John Wiley & Sons

Glen Torridon (GT) is a geomorphic feature of Aeolis Mons (informally Mt. Sharp) in Gale crater, Mars, variably covered by local regolith and wind-blown basaltic sands. The Mars Reconnaissance Orbiter’s Compact Imaging Spectrometer for Mars (CRISM) detected clay minerals in GT, making GT a target of investigation by the Mars Science Laboratory (MSL) rover, Curiosity, which confirmed a large abundance of clays. The MSL Dynamic Albedo of Neutrons (DAN) instrument observed enrichments in bulk subsurface ( < 50 cm) hydration along the rover traverse compared to lower stratigraphic sections of Mt. Sharp. Here, we investigate the relationship between the CRISM 3 μm hydration index and DAN results, taking into consideration the different spatial scales and effective depths of these two instruments. We show that the elevated hydration observed by CRISM in one area of GT corresponds to elevated DAN-derived hydration, while the lower CRISM hydration in another area of GT does not correspond to a significantly lower DAN-derived hydration. We find that CRISM measured lower hydration in areas with rough surface texture and sand cover, while DAN bulk hydration is relatively insensitive to these characteristics. DAN active neutron results also show that the stratigraphically higher section of GT has significantly higher neutron absorption, which could be due to Fe- and Mn-rich diagenetic features. Additionally, DAN results show that GT is enriched in hydrogen with respect to other, less clay-rich units observed throughout the traverse, suggesting that subsurface clay minerals could be a significant reservoir for the hydration measured by DAN in GT.

¹Michael T. Thorpe et al. (>10)
Journal of Geophysical Research (Planets)(in Press) Link to Article [https://doi.org/10.1029/2021JE007099]
¹Texas State University, JETS, at NASA Johnson Space Center, Houston, TX, 77058 USA
Published by arrangement with John Wiely & Sons

The Glen Torridon (GT) region in Gale crater, Mars is a region with strong clay mineral signatures inferred from orbital spectroscopy. The CheMin X-ray diffraction (XRD) instrument onboard the Mars Science Laboratory rover, Curiosity, measured some of the highest clay mineral abundances to date within GT, complementing the orbital detections. GT may also be unique because in the XRD patterns of some samples, CheMin identified new phases, including: (i) Fe-carbonates, and (ii) a phase with a novel peak at 9.2 Å. Fe-carbonates have been previously suggested from other instruments onboard, but this is the first definitive reporting by CheMin of Fe-carbonate. This new phase with a 9.2 Å reflection has never been observed in Gale crater and may be a new mineral for Mars, but discrete identification still remains enigmatic because no single phase on Earth is able to account for all of the GT mineralogical, geochemical, and sedimentological constraints. Here, we modeled XRD profiles and propose an interstratified clay mineral, specifically greenalite-minnesotaite, as a reasonable candidate. The coexistence of Fe-carbonate and Fe-rich clay minerals in the GT samples supports a conceptual model of a lacustrine groundwater mixing environment. Groundwater interaction with percolating lake waters in the sediments is common in terrestrial lacustrine settings, and the diffusion of two distinct water bodies within the subsurface can create a geochemical gradient and unique mineral front in the sediments. Ultimately, the proximity to this mixing zone may have controlled the secondary minerals preserved in sedimentary rocks exposed in GT.

¹Xiaoguang Li¹Yi Chen,²Xu Tang,²Lixin Gu,¹Jiangyan Yuan,¹Wen Su,³Hengci Tian,⁴Huiqian Luo,¹Shuhui Cai,⁵Sridhar Komarneni
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2022.115299]
¹State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
²Electron Microscope Laboratory, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
³Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
⁴Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
⁵Department of Ecosystem Science and Management and Materials Research Institute, 204 Energy and the Environment Laboratory, The Pennsylvania State University, University Park, PA 16802, USA
Copyright Elsevier

Troilite is one type of FeS polymorph formed under reducing environmental conditions. However, its phase transition by laser heating during Raman analysis has not been investigated in detail. This study focuses on identifying changes to Raman spectra of troilite resulted by laser heating during Raman analysis so as to determine optimized analytical conditions for characterizing iron sulfides. We comfirm that iron sulfides exposed in air are easily transformed to magnetite and hematite after a high-power laser (> 200 mW/μm² for pyrite and > 14 mW/μm² for troilite) irradiation. Troilite crystal structure is also broken easily by laser (>12 mW/μm²) under the vacuum conditions due to the volatilization of S and Fe, possibly inducing the formation of nanophase metallic iron. Therefore, iron sulfides are expected to be sensitive to laser heating. Here, we have confirmed the laser heating effect through a set of heating experiments from ambient temperature to 500 °C with various laser powers. Our results suggest that Raman analysis for troilite should be performed with a low laser power of <1.50 mW (12 mW/μm²) both in air and vacuum environments. The heating effects on troilite phase transition can be responsible for the formation of magnetite, hematite, and nanophase metallic iron in lunar samples. The thermally induced phase transition of troilite observed in this study is important because it undoubtedly modifies both the redox state and magnetic property of extraterrestrial samples and would trigger a misleading interpretation of planetary evolution.

¹Delphine Losno,¹Caroline Fitoussi,¹Bernard Bourdon
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.10.002]
¹Laboratoire de Géologie de Lyon, Terre, Planètes, Environnement, ENS de Lyon, UCBL, CNRS 46 Allée d’Italie, 69364 Lyon cedex 07, France
Copyright: Elsevier

Accretion of terrestrial planets involved partial or global melting events such as magma oceans or magma ponds. Mars experienced large-scale differentiation very early in its history, as shown by its 146Sm-142Nd and 182Hf-182W record. The broad variations in ε142Nd and ε142W of SNC meteorites highlight the presence of mantle sources that must have remained isolated, at least partly, after the crystallization of a global magma ocean. In this study, we have investigated whether the crystallization of the martian magma ocean could have generated mantle reservoirs characterized by different silicon isotope signatures, as the fractionation of Si isotopes between minerals and melts is known to depend on pressure. Thus, the goal of this study was to investigate whether there were any relationships between magma ocean crystallisation and possible variations in the Si isotope record of SNC meteorites. High resolution silicon isotope measurements were performed on twelve meteorites from the Shergottite, Nakhlite and Chassignite groups using a Neptune Plus MC-ICP-MS in dry plasma mode. The δ30Si values are in good agreement with previous studies but display a narrower range of variations with a mean value at -0.46 ‰ ± 0.07 (2SD). A magma ocean crystallization model shows that the range of δ30Si in SNCs is consistent with that generated by magma ocean crystallisation. In particular, there is a correlation between calculated 147Sm/144Nd for the moderately depleted mantle sources with δ30Si values; this correlation is consistent with the crystallization model if one includes trapped melt in the cumulates. In contrast, enriched shergottites displayed a very homogenous composition in Sm/Nd ratios, despite significant variability in δ30Si. This observation could be related to either fluid-rock interactions or redox effect during magma differentiation. Altogether, silicon isotope compositions of SNC provide new constraints about magma ocean crystallization processes in Mars.

^1,2François L.H.Tissot,^1,3Max Collinet,^4,5Olivier Namur,¹Timothy L.Grove
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://www.sciencedirect.com/science/article/abs/pii/S0016703722005178]
¹Department of the Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139, USA
²The Isotoparium, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA
³Institute of planetary research, German Aerospace Center (DLR), Rutherfordstaße 2, 12489 Berlin, Germany
⁴Institute of Mineralogy, Leibniz University Hannover, Callinstrasse 3, 30167 Hannover, Germany
⁵Department of Earth and Environmental Sciences, KU Leuven, Celestijnenlaan 200e, 3001 Heverlee, Belgium
Copyright Elsevier

Angrites are silica-undersaturated achondrites formed very early in the history of the Solar System, and the most volatile-depleted known meteorites. As such, the study of angrites can provide critical insights into the early stages of planetary formation, melting and differentiation. Yet, understanding the origins of angrites and the nature of their parent body has long been hindered by the initially small number of specimens available. Here, we leverage (i) the rapidly growing number of known angrites, and (ii) equilibrium crystallization experiments at various pressure, temperature and oxygen fugacity conditions (P-T-fO2), to revisit the petrogenesis of angrites and constrain key features of the angrite parent body (APB), such as its composition and size.

We observe that quenched (i.e., volcanic) angrites define two compositional groups, which we show are readily related by fractional crystallization. This crystallization trend converges on an olivine-clinopyroxene-plagioclase (Ol + Cpx + Plag) multiple saturation boundary, whose composition is sampled by D’Orbigny, Sahara 99555 and NWA 1296. Using the observation that some quenched specimens represent primitive angritic melts, we derive a self-consistent bulk composition for the APB. We find that this composition matches the proposed Mg/Si ratio of 1.3 derived from the angrite δ30Si values, and yields a core size (18 ± 6 wt%) in agreement with the siderophile elements depletion in the APB mantle. Our results support a primary control of nebular fractionation (i.e., partial condensation) on the composition of the APB. To establish the liquid phase equilibria of angrites, a series of 1 atmosphere and high-pressure crystallization experiments (piston cylinder and internally heated pressure vessel) was performed on a synthetic powder of D’Orbigny. The results suggest that the APB was a large (possibly Moon-sized) body, formed from materials condensed at relatively high-temperature (∼1300-1400 K), and whose fO2 changed from mildly reducing (∼IW-1.5) to relatively oxidizing (∼IW+1±1) in the ∼3 Myr between its core formation and the crystallization of D’Orbigny-like (Group 2) angrites. Based on its timing of accretion and differentiation, its composition, redox, and size, we argue that the APB represents the archetype of the first-generation of refractory-enriched planetesimals and embryos formed in the innermost part of the inner Solar System (<1 AU), and which accreted in the telluric planets.

¹Harvey Pickard et al. (>10)
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.09.041]
¹Department of Earth Science & Engineering, Imperial College London, London SW7 2AZ, UK
Copyright Elsevier

Zinc and Cd isotope compositions are presented for a comprehensive suite of terrestrial rocks to constrain the extent of Zn and Cd isotope fractionation during igneous processes and better define the δ66Zn and δ114Cd values of the silicate Earth (the δ values denote per mille deviations of 66Zn/64Zn from JMC Lyon Zn and of 114Cd/110Cd from NIST SRM 3108 Cd). Analyses of spinel lherzolites provide a bulk silicate Earth (BSE) δ114CdBSE value of –0.06 ± 0.03‰ (2SD). For Zn, the peridotite data of the current and previous studies define a mean δ66ZnBSE = 0.20 ± 0.05‰ (2SD). Komatiite analyses of this and published investigations yield similar mean values, which suggests that the Zn and Cd isotope compositions of the mantle remained fairly constant since the Archean. Data for loess provide upper continental crust compositions of δ114Cd = 0.03 ± 0.10‰ and δ66Zn = 0.23 ± 0.07‰. The Zn isotope and abundance data for peridotites and oceanic basalts are in accord with the previous observation of a mantle array, with basalts having higher Zn concentrations and δ66Zn values than the peridotites. To a first order, this reflects slightly incompatible behaviour of Zn during mantle melting and melt differentiation with associated enrichment of heavy Zn isotopes in the melt phase. Cadmium is marginally more incompatible than Zn during igneous processes and the oceanic basalts also display a minor enrichment of heavy Cd isotopes relative to peridotites. However, secondary processes produce significant Cd isotope variability in both mantle melts and peridotites, obscuring the primary igneous array. The δ66ZnBSE estimates of this and previous studies resemble the Zn isotope compositions of CV and CO carbonaceous and some enstatite chondrites. In contrast, the BSE has a lower δ114CdBSE value than enstatite and carbonaceous chondrites. This implies that the Cd isotope composition of the BSE was either fractionated during accretion or that Earth’s Cd inventory was not exclusively acquired from material related to carbonaceous and enstatite chondrites. Importantly, delivery of Zn and Cd to the BSE solely by CI and CM chondrites is not in accord with the meteorite and terrestrial stable isotope data of these elements.

¹A.Morlok,²K.H.Joy,²D.Martin,²R.Wogelius,¹H.Hiesinger
Planetary and Space Science (in Press) Link to Article [https://doi.org/10.1016/j.pss.2022.105576]
¹Institut für Planetologie, Wilhelm-Klemm-Strasse 10, 48149, Münster, UK
²Department of Earth and Environmental Sciences, School of Natural Sciences, The University of Manchester, Manchester, M13 9PL, UK

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^1,2Margriet L. Lantink,^3,4Joshua H. F. L. Davies,³Maria Ovtcharova,¹Frederik J. Hilgen
PNAS 119, e2117146119 Link to Article [https://doi.org/10.1073/pnas.2117146119]
¹Department of Earth Sciences, Utrecht University, Utrecht, 3584 CB The Netherlands
²Department of Geoscience, University of Wisconsin–Madison, Madison, WI 53706.
³Department of Earth Sciences, University of Geneva, CH-1205 Geneva, Switzerland
⁴Département des sciences de la Terre et de l’atmosphère/Geotop, Université du Québec à Montréal, Montréal, QC H2X 3Y7, Canada

The long-term history of the Earth–Moon system as reconstructed from the geological record remains unclear when based on fossil growth bands and tidal laminations. A possibly more robust method is provided by the sedimentary record of Milankovitch cycles (climatic precession, obliquity, and orbital eccentricity), whose relative ratios in periodicity change over time as a function of a decreasing Earth spin rate and increasing lunar distance. However, for the critical older portion of Earth’s history where information on Earth–Moon dynamics is sparse, suitable sedimentary successions in which these cycles are recorded remain largely unknown, leaving this method unexplored. Here we present results of cyclostratigraphic analysis and high-precision U–Pb zircon dating of the lower Paleoproterozoic Joffre Member of the Brockman Iron Formation, NW Australia, providing evidence for Milankovitch forcing of regular lithological alternations related to Earth’s climatic precession and orbital eccentricity cycles. Combining visual and statistical tools to determine their hierarchical relation, we estimate an astronomical precession frequency of 108.6 ± 8.5 arcsec/y, corresponding to an Earth–Moon distance of 321,800 ± 6,500 km and a daylength of 16.9 ± 0.2 h at 2.46 Ga. With this robust cyclostratigraphic approach, we extend the oldest reliable datum for the lunar recession history by more than 1 billion years and provide a critical reference point for future modeling and geological investigation of Precambrian Earth–Moon system evolution.