Thallium isotopes in early diagenetic pyrite – a paleoredox proxy?

Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Geochimica et Cosmochimica Acta 75 (2011): 6690-6704, doi:10.1016/j.gca.2011.07.047.This paper presents the first study of Tl isotopes in early diagenetic pyrite. Measurements from two sections deposited during the Toarcian Ocean Anoxic Event (T-OAE, ~183Ma) are compared with data from Late Neogene (<10Ma) pyrite samples from ODP legs 165 and 167 that were deposited in relatively oxic marine environments. The Tl isotope compositions of Late Neogene pyrites are all significantly heavier than seawater, which most likely indicates that Tl in diagenetic pyrite is partially sourced from ferromanganese oxy-hydroxides that are known to display relatively heavy Tl isotope signatures. One of the T-OAE sections from Peniche in Portugal displays pyrite thallium isotope compositions indistinguishable from Late Neogene samples, whereas samples from Yorkshire in the UK are depleted in the heavy isotope of Tl. These lighter compositions are best explained by the lack of ferromanganese precipitation at the sediment–water interface due the sulphidic (euxinic) conditions thought to be prevalent in the Cleveland Basin where the Yorkshire section was deposited. The heavier signatures in the Peniche samples appear to result from an oxic water column that enabled precipitation of ferromanganese oxy-hydroxides at the sediment–water interface. The Tl isotope profile from Yorkshire is also compared with previously published molybdenum isotope ratios determined on the same sedimentary succession. There is a suggestion of an anti-correlation between these two isotope systems, which is consistent with the expected isotope shifts that occur in seawater when marine oxic (ferromanganese minerals) fluxes fluctuate. The results outlined here represent the first evidence that Tl isotopes in early diagenetic pyrite have potential to reveal variations in past ocean oxygenation on a local scale and potentially also for global oceans. However, much more information about Tl isotopes in different marine environments, especially in anoxic/euxinic basins, is needed before Tl isotopes can be confidently utilized as a paleo-redox tracer.SGN is funded by a NERC fellowship

The Woody Guthrie Centennial Bibliography

This bibliography updates two extensive works designed to include comprehensively all significant works by and about Woody Guthrie. Richard A. Reuss published A Woody Guthrie Bibliography, 1912–1967 in 1968 and Jeffrey N. Gatten\u27s article “Woody Guthrie: A Bibliographic Update, 1968–1986” appeared in 1988. With this current article, researchers need only utilize these three bibliographies to identify all English-language items of relevance related to, or written by, Guthrie

The James Webb Space Telescope Mission

Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least $4m$. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the $6.5m$ James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 years, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space Telescope Overview, 29 pages, 4 figure

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Leveraging Open Science Machine Learning Challenges for Data Constrained Planetary Mission Instruments

International audienceWe set up two open-science machine learning (ML) challenges focusing on building models to automatically analyze massspectrometry (MS) data for Mars exploration. ML challenges provide an excellent way to engage a diverse set of experts withbenchmark training data, explore a wide range of ML and data science approaches, and identify promising models based onempirical results, as well as to get independent external analyses to compare to those of the internal team. These two challengeswere proof-of-concept projects to analyze the feasibility of combining data collected from different instruments in a singleML application. We selected mass spectrometry data from 1) commercial instruments and 2) the Sample Analysis at Mars(SAM, an instrument suite that includes a mass spectrometer subsystem onboard the Curiosity rover) testbed. These challenges,organized with DrivenData, gathered more than 1,150 unique participants from all over the world, and obtained more than 600solutions contributing powerful models to the analysis of rock and soil samples relevant to planetary science using various massspectrometry datasets. These two challenges demonstrated the suitability and value of multiple ML approaches to classifyingplanetary analog datasets from both commercial and flight-like instruments.We present the processes from the problem identification, challenge setups, and challenge results that gathered creative anddiverse solutions from worldwide participants, in some cases with no backgrounds in mass spectrometry. We also present thepotential and limitations of these solutions for ML application in future planetary missions. Our longer-term goal is to deploythese powerful methods onboard the spacecraft to autonomously guide space operations and reduce ground-in-the-loop reliance

The Organics of Mars

International audienceOur understanding of organic matter on Mars has evolved from presumed ‘missing organic molecules’ based on Viking data to a robust library of organic molecules detected over the last decade by the SAM (Sample Analysis at Mars) instrument suite onboard the Mars Science Laboratory (MSL) rover, as well as from studies of Mars meteorites. Additionally, recent findings by the Perseverance rover suggest the possibility of simple organics in data from the SHERLOC (Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals) fluorescence and Raman spectrometer. Here, we explore the current state of knowledge of organics on Mars from the perspective of in situ characterization with landed instruments, and the potential for new leaps in that knowledge with Mars Sample Return.MSL detections of organics in Gale crater mudstone and sandstones include chlorohydrocarbons up to 300 ppbw; small aliphatic, aromatic, and, sulfur-containing compounds (at 0.1-10 ppmw detections) potentially originating from macromolecular organics and long-chain alkanes from C10 to C12. Total abundance of C is likely higher than individual molecular detections and on the order of 100’s of ppmw. The recent TMAH wet chemistry experiment liberated macromolecular organics, resulting in the detection of one to two-ring aromatic compounds, benzoic acid methyl ester, and benzothiophene. All these detections confirmed the presence of organics in the Martian subsurface, despite exposure to ionizing radiation for at least 80 My.More recent findings from the SHERLOC instrument onboard the Mars2020 rover include fluorescence and Raman spectra that may be consistent with one- and two-ring organic molecules, although other inorganic sources for the spectra are possible.The next-generation instruments onboard the ExoMars rover (Raman, MicrOmega spectrometer and MOMA chemical analyzer), combined with a 2-meter drill, will enable investigation of better protected subsurface samples. The two current in situ organics detection techniques are quite different, but Mars Sample Return in the mid-2030s would provide the first groundtruth of these data, enable the search for other organic molecules that are not detectable by in situ instrumentation, and address fundamental outstanding questions about the origin of organics on Mars

The Organics of Mars

International audienceOur understanding of organic matter on Mars has evolved from presumed ‘missing organic molecules’ based on Viking data to a robust library of organic molecules detected over the last decade by the SAM (Sample Analysis at Mars) instrument suite onboard the Mars Science Laboratory (MSL) rover, as well as from studies of Mars meteorites. Additionally, recent findings by the Perseverance rover suggest the possibility of simple organics in data from the SHERLOC (Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals) fluorescence and Raman spectrometer. Here, we explore the current state of knowledge of organics on Mars from the perspective of in situ characterization with landed instruments, and the potential for new leaps in that knowledge with Mars Sample Return.MSL detections of organics in Gale crater mudstone and sandstones include chlorohydrocarbons up to 300 ppbw; small aliphatic, aromatic, and, sulfur-containing compounds (at 0.1-10 ppmw detections) potentially originating from macromolecular organics and long-chain alkanes from C10 to C12. Total abundance of C is likely higher than individual molecular detections and on the order of 100’s of ppmw. The recent TMAH wet chemistry experiment liberated macromolecular organics, resulting in the detection of one to two-ring aromatic compounds, benzoic acid methyl ester, and benzothiophene. All these detections confirmed the presence of organics in the Martian subsurface, despite exposure to ionizing radiation for at least 80 My.More recent findings from the SHERLOC instrument onboard the Mars2020 rover include fluorescence and Raman spectra that may be consistent with one- and two-ring organic molecules, although other inorganic sources for the spectra are possible.The next-generation instruments onboard the ExoMars rover (Raman, MicrOmega spectrometer and MOMA chemical analyzer), combined with a 2-meter drill, will enable investigation of better protected subsurface samples. The two current in situ organics detection techniques are quite different, but Mars Sample Return in the mid-2030s would provide the first groundtruth of these data, enable the search for other organic molecules that are not detectable by in situ instrumentation, and address fundamental outstanding questions about the origin of organics on Mars