Improved collection of rooftop micrometeorites through optimized extraction methods: The Budel collection

1Guido Jonker,1Roel van Elsas,1Jeroen H. J. L. van der Lubbe,1Wim van Westrenen
Meteoritics & Planetary Science (in Press) Open Access Link to Article []
1Department of Earth Sciences, Faculty of Science, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands
Published by arrangement with John Wiley & Sons

The scientific value of micrometeorites collected from deep-sea sediments or glacial deposits can be limited by poorly constrained accumulation times or severe alteration, coupled with a complex infrastructure of sampling expeditions. Collecting micrometeorites from rooftops has recently become a feasible alternative, but extraction methods have not been optimized or standardized to date. Here, we show that existing methods for the recovery of melted cosmic spherules (CSs) can be strongly improved by using a sequence of mineral separation techniques, including shape separation with an asymmetric vibrator and heavy liquid density separation with overflow centrifuges. We retrieved 1006 micrometeorites from the gutter of a barn in Budel, the Netherlands. Particle diameters are 80–515 μm, with the major mode at 130 μm and a slope exponent of −4.88. Differences in size distributions among various types of CSs indicate a multi-source influx, with CS textures controlled by their parent body’s mineralogy and orbital parameters. Repeated sampling of the rooftop after accumulation times of 959 and 333 days allows for a time-integrated global mass flux estimate of 472 t year−1. This estimate is notably higher than previous rooftop-based estimates but is still severely affected by micrometeorite loss from the gutter through drainage. The mass flux peaks at an equivalent particle diameter of ~200 μm. The Budel collection is the first rooftop collection to contain abundant vitreous micrometeorites and include the coarse-grained S-type CS class. Unmelted and I-type micrometeorites remain difficult to extract from rooftop samples. Vitreous micrometeorites display various stages of weathering, showing that severe alteration of glass can progress at a faster rate in populated regions than previously assumed. This study demonstrates that methodological adjustments can drastically increase the scientific potential of rooftop micrometeorite collections.

An Examination of Soil Crusts on the Floor of Jezero Crater, Mars

1E.M.Hausrath et al. (>10)
Journal of Geophysical Research (Planets) (in Press) Link to Article []
1Department of Geoscience, University of Nevada, Las Vegas, Nevada, 89154 USA
Published by arrangement with John Wiley & Sons

Martian soils are critically important for understanding the history of Mars, past potentially habitable environments, returned samples, and future human exploration. This paper examines soil crusts on the floor of Jezero crater encountered during initial phases of the Mars 2020 mission. Soil surface crusts have been observed on Mars at other locations, starting with the two Viking Lander missions. Rover observations show that soil crusts are also common across the floor of Jezero crater, revealed in 45 of 101 locations where rover wheels disturbed the soil surface, 2 out of 7 helicopter flights that crossed the wheel tracks, and 4 of 8 abrasion/drilling sites. Most soils measured by the SuperCam laser-induced breakdown spectroscopy (LIBS) instrument show high hydrogen content at the surface, and fine-grained soils also show a visible/near infrared (VISIR) 1.9 µm H2O absorption feature. The Planetary Instrument for X-ray Lithochemistry (PIXL) and SuperCam observations suggest the presence of salts at the surface of rocks and soils. The correlation of S and Cl contents with H contents in SuperCam LIBS measurements suggests that the salts present are likely hydrated. On the “Naltsos” target, magnesium and sulfur are correlated in PIXL measurements, and Mg is tightly correlated with H at the SuperCam points, suggesting hydrated Mg-sulfates. Mars Environmental Dynamics Analyzer (MEDA) observations indicate possible frost events and potential changes in the hydration of Mg-sulfate salts. Jezero crater soil crusts may therefore form by salts that are hydrated by changes in relative humidity and frost events, cementing the soil surface together.

The Ries impact and its distal effects in sediments of Central Europe—A review

1,2Jan-Michael Lange, 1Peter Suhr
Meteoritics & Planetary Science (in Press) Open Access Link to Article []
1Senckenberg Naturhistorische Sammlungen Dresden, Dresden, Germany
2Institut für Mineralogie, Technische Universität Bergakademie Freiberg, Freiberg, Germany
Published by arrangement with John Wiley & Sons

The Ries impact is the most important cosmic event in the younger geological history of Europe. Its effects reach far beyond the area considered so far and are documented in manifold evidence. In this paper, the widely scattered reports in the literature are compiled and supported with investigations by the authors. Besides well-known ejecta features like the Brockhorizont, Reuter’s blocks, and moldavites, little known or forgotten indications, like a lechatelierite and β-cristobalite occurrence in Bavaria and unusual sedimentation phenomena in northern Germany, are presented. The paleogeographic reconstruction shows that the Ries impact occurred on the southern side of the Neogene Central European mainland. Large parts of this erosional area were devastated by the impact. Pressure waves and thermal radiation had a lasting effect on the landscape within hundreds of kilometers around the impact site. Destruction of the vegetation cover by impact-induced storms, wildfires, and heavy rainfall generated intense erosion. The adjacent sedimentation area to the north (Paleo-North Sea) experienced an increased and short-term supply of terrestrial debris to the marine environment. The stratigraphic coincidence of these exceptional sediments with the Ries event leads us to conclude that the distal effects of the impact are present here, which have so far received little or no attention in this context. The paper considers the different indications and sets them in a large-scale context.

Global surficial water content stored in hydrated silicates at Mars from OMEGA/MEx

1,2Lucie Riu,2,3John Carter,2François Poulet,1Alejandro Cardesín-Moinelo,1Patrick Martin
Icarus (in Press) Link to Article []
1European Space Agency (ESA), European Space Astronomy Centre (ESAC), Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada, Madrid, Spain
2Institut d’Astrophysique Spatiale (IAS), Université Paris-Saclay, Orsay, France
3Aix-Marseille Université, CNRS, CNES, LAM, Marseille, France
Copyright Elsevier

Assessing the water content at the surface of Mars is key to understand the history of water and past climate of the planet but it also is very important for future exploration and potential In Situ Resource Utilization (ISRU). Numerous locations on the surface, known to harbor hydrated minerals, have been detected and their mineralogical assemblages quantified. Based on previous analyses resulting from the modelling of OMEGA near-infrared spectra, we evaluated in this paper the amount of water that could still be stored in those hydrated minerals that were previously characterized. Overall, we find that on average at the surface the hydrated silicates are composed of ~5 wt% of water with specific regions with >20 wt% localized in 100 m2 areas, that could present a higher ISRU potential. We find that the global amount of water estimated in hydrated silicates corresponds to ~10−4 Global Equivalent Layer (m) for deposits of 1 m in depth, which represents a lower bound but could still indicate that on the surface the hydrated silicates – as detected by OMEGA (< 1% of the surface) – may not globally be an important sink of water.

An inner solar system origin of volatile elements in Mars

1,2Thorsten Kleine,2Theodor Steller,1,2Christoph Burkhardt,3Francis Nimmo
Icarus (in Press) Link to Article []
1Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
2Institut für Planetologie, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany
3Department of Earth and Planetary Sciences, University of California Santa Cruz, Santa Cruz, CA 95064, USA
Copyright Elsevier

The origin of volatile elements in Mars and whether these elements derive from the inner or outer solar system is unclear. Here we show that Mars exhibits nucleosynthetic zinc (Zn) isotope anomalies similar to those of non‑carbonaceous (NC) but distinct from carbonaceous (CC) meteorites. Like for non-volatile elements, Mars’ Zn isotope composition is intermediate between those of enstatite and ordinary chondrites, demonstrating that Mars acquired volatile elements predominantly from its inner solar system building blocks. The Zn isotope data limit the contribution of CI chondrite-like material to Mars to 4% by mass at most and show that Mars accreted less CC material than Earth. The origin of these disparate CC fractions is unclear, but can place constraints on how and when CC-type material was delivered to the inner solar system.

Titanium and chromium isotopic compositions of calcium-aluminum-rich inclusions: Implications for the sources of isotopic anomalies and the formation of distinct isotopic reservoirs in the early Solar System

1Zachary A. Torrano,2Gregory A. Brennecka,1Cameron M. Mercer,1Stephen J. Romaniello,1Vinai K. Rai,1Rebekah R. Hines,1Meenakshi Wadhwa
Geochimica et Cosmochimica Acta (in Press) Link to Article []
1School of Earth and Space Exploration, Arizona State University, Tempe, AZ, 85287
2Lawrence Livermore National Laboratory, Livermore, CA, 94550
Copyright Elsevier

As the earliest-dated solids in our Solar System, calcium-aluminum-rich inclusions (CAIs) provide a record of their formation environment near the young Sun and hold clues to the formation of planetary-scale isotopic reservoirs in the solar protoplanetary disk. Although CAIs from several CV, CK, CM, CO, and ordinary chondrites have been analyzed previously for their Ti isotopic compositions, CAIs from just three CV chondrites have been analyzed for their Cr isotopic compositions, and only a handful of CAIs have been measured for both their Ti and Cr isotopic compositions. We report mass-independent Ti and Cr isotopic anomalies in several CAIs from CV and CK chondrites; this is the first report of the Cr isotopic composition of a CAI from a CK chondrite. With these additional data, we aim to better constrain the compositional range of CAIs in ε50Ti versus ε54Cr space, thereby facilitating the isotopic characterization of the material inherited by the solar protoplanetary disk and the role of CAIs in the formation of distinct planetary-scale isotopic reservoirs in our early Solar System. The narrow range in isotopic anomalies in CAIs when compared to other early-formed refractory inclusions such as platy hibonite crystals (PLACs) and spinel-hibonite inclusions (SHIBs) suggests that CAIs record the mixing of these precursor materials and the averaging of their larger isotopic anomalies. The isotopic composition of CAIs is therefore likely the result of a combination of factors, including mixing of material inherited from their formation region, heterogeneous carrier phase distribution, and thermal processing in the disk. The ε50Ti and ε54Cr isotopic compositions of CAIs are not correlated, further demonstrating that these isotopic anomalies have different carrier phases. The Ti and Cr isotopic compositions of CAIs additionally show that CAIs alone cannot be responsible for the compositional difference between the non-carbonaceous chondritic (NC) and carbonaceous chondritic (CC) isotopic reservoirs but nevertheless do play a role in the formation of these large-scale isotopic reservoirs in the early Solar System.

Lewis Cliff 87223, an anomalous enstatite chondrite and the diversity of enstatite chondrites

1,2Kaitlyn R. Goss,2,3Mabel L. Gray,2,3,4Michael K. Weisberg,2,3Denton S. Ebel
Meteoritics & Planetary Science (in Press) Link to Article []
1Department of Geology, Mount Holyoke College, South Hadley, Massachusetts, USA
2Department of Earth and Planetary Sciences, American Museum of Natural History (AMNH), New York, New York, USA
3Department of Earth and Environmental Sciences, City University (CUNY) of New York Graduate Center, New York, New York, USA
4Department of Physical Sciences, Kingsborough Community College—CUNY, Brooklyn, New York, USA
Published by arrangement with John Wil
ey & Sons

We studied a thin section of Lewis Cliff (LEW) 87223, an unusual EL3-related, enstatite chondrite (EC) that has primary and secondary features not observed in other ECs. We studied its metal-rich nodules, possible shock features, and chondrules, eight of which are Al-rich chondrules (ARCs). LEW 87223 has petrologic and compositional features similar to EL3s. Enstatite is the dominant mineral; chondrule boundaries are well defined; Si content of metal (0.5–0.6 wt%) is consistent with typical EL3; it has Cr-bearing troilite, oldhamite, and alabandite; and its O-isotopic composition is similar to other ECs. However, metal abundance in LEW 87223 (~13 vol%) is slightly higher than in other EL3s and its metal nodules are texturally and mineralogically different from other ECs. Both high and low Ni metals are present, and its alabandite has higher Fe (27.8 wt% Fe) than in other EL3s. Silicates appear darkened in plane polarized light, largely due to reduction of Fe from silicate. A remarkable feature of LEW 87223 is the high abundance of ARCs, which contain Ca-rich plagioclase and varying amounts of Na-rich plagioclase along chondrule edges and as veins. This suggests Na metasomatism and the possibility of hydrothermal fluids, potentially related to an impact event. LEW 87223 expands the range of known EC material. It shows that ECs are more diverse and record a wider range of parent body processes than previously known. LEW 87223 is an anomalous EL3, potentially the first member of a new EC group should similar samples be discovered.

A novel algorithm for mapping carbonates using CRISM hyperspectral data

1Sandeepan Dhoundiyal,1,2Alok Porwal,3C.V. Niveditha,3Guneshwar Thangjam,1Malcolm Aranha1, Shivam Kumar,1Debosmita Paul,1R. Kalimuthu
Icarus (in Press) Link to Article []
1Centre of Studies in Resources Engineering, Indian Institute of Technology Bombay, Mumbai, Maharashtra 400076, India
2Centre for Exploration Targeting, University of Western Australia, Crawley 6009, Western Australia, Australia
3National Institute of Science Education and Research, HBNI, Bhubaneswar 752050, India
Copyright Elsevier

The algorithms for mapping carbonates from Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) data use the depths of the diagnostic carbonate absorption features at ~2.3 μm and ~ 2.5 μm. However, because the band depths are estimated using fixed shoulder wavelengths, subtle shifts in band centres caused by different cations in the carbonates could result in false negatives for carbonates or false positives for other minerals that have absorption features in a similar wavelength range (eg. phyllosilicates, zeolites). This paper proposes a new algorithm that is based on the following attributes of carbonate spectra in the 2.0 to 3.0 μm range: (1) presence of two diagnostic overtones features around ~2.3 μm and ~2.5 μm; however, these features may show red shift or blue shift depending on the nature of cation(s); (2) the inter band gap between ~2.3 μm and ~2.5 μm carbonate absorption features, which remains relatively constant at ~0.2 μm, even if there is a shift in the absorption features; (3) the contiguity of these two features, that is, carbonate spectra do not show any absorption features in between the above two features. The algorithm also includes a novel geometric continuum removal technique for locating the absorption features. The effectiveness of the algorithm is demonstrated using laboratory spectra, CRISM machine learning toolkit’s mineral dataset, as well as CRISM images. The true positive rate (TPR), true negative rate (TNR) and overall accuracy for the method over the CRISM machine learning toolkit’s mineral dataset are 29%, 87% and 83%, respectively.