Search

A study of 50 boys with fragile X syndrome, their parents, and teachers, found early intervention started on average at 21.6 months and there was a steady increase in the amount of early intervention across age periods. Although parents reported satisfaction with services, most would have preferred more services. (Contains references.) (Author/CR)

A study of 57 boys with fragile X syndrome (ages 24-133 months) assessed the extent to which autism and autistic features were evident using the Childhood Autism Rating Scale (CARS). Fourteen subjects scored above the cut-off for autism, with 12 of the 14 in the mildly or moderately autistic range. (Author/CR)

The Oman Drilling Project established an "Active Alteration" multi‐borehole observatory in peridotites undergoing low‐temperature serpentinization in the Samail Ophiolite. The highly serpentinized rocks are in contact with strongly reducing fluids. Distinct hydrological regimes, governed by differences in rock porosity and fracture density, give rise to steep redox (Eh +200 to −750 mV) and pH (pH range 8.5–11.2) gradients within the 300–400 m deep boreholes. The serpentinites and fluids host an active subsurface ecosystem. Microbial cell abundances in serpentinite vary at least six orders of magnitude, from ≤3.5 × 101 to 2.9 × 107 cells/g. Low levels of biological sulfate reduction (2–1,000 fmol/cm3/day) can be detected in rock cores, particularly in rocks in contact with reduced groundwaters with pH < 10.5. Thermodesulfovibrio is the predominant sulfate reducer identified via metagenomic sequencing of adjacent groundwater communities. We infer that transport and reaction of microbially generated sulfide with the serpentine and brucite assemblages gives rise to optical darkening and sulfide overprinting, including the formation of tochilinite‐vallerite group minerals, potentially serving as an indicator that this system is inhabited by microbial life. Olivine mesh‐cores replaced with ferroan brucite and minor awaruite, abundant veins containing hydroandradite garnet and polyhedral serpentine, and late‐stage carbonate veins are suggested as targets for future spatially resolved life‐detection investigations. The high‐quality whole‐round core samples that have been preserved can be further probed to define how life distributes itself and functions within a system where chemical disequilibria are sustained by low‐temperature water/rock interaction, and how biosignatures of in situ microbial activity are generated. Plain Language Summary: Ultramafic rocks undergoing water/rock interaction, and storing fluids that are far from chemical equilibrium, may be one of the most common habitats in our solar system. Through the Oman Drilling Project we collected >1 km of intact serpentinite in contact with groundwaters. These cores capture parts of the rock‐hosted biosphere and show how cells are distributed within serpentinites that vary in their mineralogical, physical and chemical properties. The cores are also biologically active, enabling us to detect specific metabolisms, such as when microorganisms combine hydrogen as reductant and sulfate as an oxidant to fuel their metabolism. Although the distribution of microbial cells in the rock cores is very heterogeneous, there are many intervals where the abundance of cells constitutes robust biomass. In the deeper cores, slow, albeit detectable, microbial sulfate reduction proceeds. We suggest that this pervasive biological activity releases byproducts such as sulfide that can react with the serpentinite and change the optical and chemical properties of the rocks. The feedbacks between the rock alteration and microbial activity produce markers that enable us to focus our search for rock‐hosted life and any specific biosignatures it may produce on Earth and perhaps on other planetary bodies. Key Points: Highly serpentinized subsurface rocks exhibit steep redox gradients and host microbial cell abundances that vary >6 orders of magnitudeLow rates of microbial sulfate reduction in rock cores are inferred to result in optical darkening and sulfide overprinting of the mineralogyWidespread andradite garnet, abundant ferroan brucite, and rare carbonate are targets for future spatially resolved life‐detection efforts [ABSTRACT FROM AUTHOR]

Serpentinized peridotite is reacting with groundwater in the subsurface of the Samail ophiolite in Oman. Although these rocks are partially to completely serpentinized, they interact with a groundwater aquifer containing hyperalkaline fluids rich in H2 and CH4. Since the mechanisms by which H2 production may continue at low temperatures (<50°C) are not fully understood, core recovered during the Oman Drilling Project provides an excellent opportunity to study the mineralogy and Fe speciation in highly serpentinized harzburgite recording multiple stages of water/rock interaction. In Hole BA3A, early hydration of olivine and pyroxene, which likely occurred at temperatures of ∼100°C–200°C, produced serpentine, Fe‐rich brucite, awaruite, and little magnetite. Notably, Fe‐rich brucite is only preserved at >∼100 m depth in the core. Fe‐rich brucite is nearly absent within two near‐surface reaction zones where later stages of reaction are recorded, which include replacement of Fe‐rich brucite by Fe(III)‐bearing serpentine, and increases in the proportion of other Fe(III)‐bearing phases such as magnetite and hydroandradite. Thus, Fe‐rich brucite at depth represents substantial stored capacity for H2 production that can continue at low temperature, even after primary olivine and pyroxene are exhausted, thereby sustaining habitable conditions for microbial life. Plain Language Summary: When ultramafic rocks from Earth's mantle come into contact with water, they undergo a set of hydration reactions leading to the formation of secondary minerals such as serpentine and brucite. Such "serpentinization reactions" also often involve the oxidation of iron, which can result in the production of hydrogen gas. Many models predict abundant hydrogen production at high temperatures >250°C, but the potential reactions that may produce hydrogen are more enigmatic at lower temperatures. Using rock cores drilled from the Samail ophiolite in Oman, we show that in highly serpentinized rocks in contact with hyperalkaline, low‐temperature, hydrogen‐rich fluids, multiple stages of reactions can be observed. By analyzing changes in mineralogy with depth, it is possible to identify reaction fronts where rocks that initially formed abundant Fe(II)‐bearing minerals such as brucite are now interacting with modern groundwaters at low‐temperature to form Fe(III)‐bearing minerals including magnetite, hydroandradite, and Fe(III)‐bearing serpentine. These reactions are likely responsible for the production of hydrogen gas that is able to support a rock‐hosted microbial community, and show that habitable conditions can be produced even during late, non‐hydrothermal stages of ultramafic rock alteration. Key Points: Subsurface serpentinites from the Samail ophiolite contain distinct reaction fronts with implications for H2 production and habitabilityWhere Fe(II)‐rich brucite is present, it has the potential to fuel future H2 productionFe(II,III)‐rich serpentine, hydroandradite, and magnetite all record past H2 production at low temperatures <200°C [ABSTRACT FROM AUTHOR]

Fe oxidation/reduction reactions play a fundamental role in a wide variety of geological processes. In natural materials, Fe redox state commonly varies across small spatial scales at reaction interfaces, yet the approaches available for quantitatively mapping the Fe redox state at the microscale are limited. We have designed an optimized synchrotron-based X‑ray spectroscopic approach that allows microscale quantitative mapping of Fe valence state by extending the Fe XANES pre-edge technique. An area of interest is mapped at nine energies between 7109–7118 eV and at 7200 eV, allowing reconstruction, baseline subtraction, and integration of the pre-edge feature to determine Fe(III)/ΣFe with 2 μm spatial resolution. By combining the Fe redox mapping approach with hyperspectral Raman mineralogy mapping, the Fe oxidation state distributions of the major mineral phases are revealed. In this work, the method is applied to a partially serpentinized peridotite with various Fe-bearing secondary mineral phases to trace the Fe transformations and redox changes that occurred during its alteration. Analysis with the Fe redox mapping technique revealed that the peridotite contained relict olivine with abundant Fe(II), while serpentine, pyroaurite, and another hydroxide phase are secondary mineral reservoirs of Fe(III). Although serpentine is not Fe-rich, it contained approximately 74% ± 14% Fe(III)/ΣFe. These analytical results are integral to interpreting the sequence of alteration reactions; serpentinization of primary olivine formed Fe(II)-rich brucite and oxidized serpentine, which could have contributed to H2 production during serpentinization. Subsequent weathering by oxidizing, CO2-bearing fluids led to the partial carbonation and oxidation of brucite, forming pyroaurite and a hydroxide phase containing dominantly Fe(III). This Fe redox imaging approach is applicable to standard petrographic thin sections or grain mounts and can be applied to various geologic and biogeochemical systems. [ABSTRACT FROM AUTHOR]

The Bacillus and Paenibacillus species isolated from Fe and Mn oxide minerals precipitating at a deep subsurface oxic-anoxic interface at Henderson Molybdenum Mine, Empire, CO were explored to understand their Mn(II)-oxidizing potential and mnxG gene that codes for a putative Mn(II)-oxidizing enzyme in Bacillus species. The data obtained revealed a complex phylogenetic distribution of the mnxG gene in which vertical inheritance and gene loss influence the distribution of the gene among the Bacillus species.

Introduction: The Mars 2020 mission is to investigate regional geology, evaluate past habitability, seek signs of ancient life, and assemble a returnable cache of samples as the Perseverance rover explores Jezero Crater, a Noachian crater on the edge of the Isidis basin that contains a deltaic system. The Perseverance rover recently completed a traverse of the floor of Jezero crater, characterizing and collecting samples from two units informally named the Máaz and Séítah formations (Cf-Fr and Cf-F1 in [1]). The Máaz fm makes up the current Jezero Floor surface, appearing to overlie the Séítah strata. Eight rock samples were collected and stored in the rover, along with proximity science observations using the rover's onboard payload about the composition, mineralogy, and texture of the sampled rocks. Seitah samples: The Séítah fm outcrops across the crater floor to the southeast of the delta. Orbital data suggested that Séítah contains olivine- and carbonate-bearing lithologies [2, 3] that may have formed by igneous, volcaniclastic, or sedimentary processes (e.g., [4-7]). Samples were collected from Brac (topographically high, within the Séítah bondaries) and Issole (topographically low, near the contact with the Máaz fm). Natural surfaces of both Brac and Issole exhibited horizontal layering at the cm- to dm-scale. They comprise densely packed, relatively coarse (1-2 mm) dark gray grains variably surrounded by lighter-toned interstitial materials. Their mineralogy is (ultra)mafic, dominated by olivine and pyroxene, with large olivine grains protruding from some natural rock surfaces. Minor (several volume %) secondary phases, including carbonates, silica phases, Mg-sulphates and Na-perchlorates, were present; ongoing work will assess the abundance of organic molecules, potentially associated with secondary mineral phases. The Seitah rocks are interpreted as olivine cumulates, extensively altered by fluids [8, 9]. Maaz samples: The Máaz fm was inferred to be volcanic because of the remote detection of olivine and pyroxene in the unit, its lobate margins, and embayment relationships [5, 10-12]; however, volcanoclastic and/or sedimentary origins were also posited [13, 14]. Three rocks in the area were sampled: Roubion, Rochette, and Sid. Roubion is in a topographically low area of flat-lying, polygonally jointed material. Rochette is located along the feature named Artuby Ridge, a resistant ledge that can be traced from near the Roubion site along the southern edge of the Séítah fm boundary. Sid represents the stratigraphically capping member of the Máaz fm, expressed as massive, blocky rocks that appear to cover much of the Jezero Crater surface. The three Máaz fm rocks are fine-to-medium grained, holocrystalline rocks dominated by pyroxene and feldspar, with an overall alkalic nature in contrast to the basaltic nature of martian meteorites (e.g., [15, 16], see also Udry et al. this conference). The mafic grain size appeared to be smallest in Roubion and coarsened upward to Sid, where several-mm, euhedral feldspar grains are visible. Roubion was pervasively altered with abundant secondary phases, Rochette and Sid contained only minor secondary phases. Mechanical competence corroborated the degree of weathering. Together, these observations imply that the Máaz fm is an igneous rock package that has experienced variable degrees of fluid interaction. Future work: The suite of the Séítah and Máaz fm samples represents a powerful outcome of the Perseverance Crater Floor campaign that will address several important objectives of the Mars Sample Return campaign [17], including magmatic history, water-rock interactions, environmental conduciveness to life, and isotopic ages for geologic events. Perseverance is now beginning its exploration of the delta facies and will place one of the returnable sample caches near the delta in the upcoming year for Mars Sample Return in the 2030s (see also Herd et al., this conference). [ABSTRACT FROM AUTHOR]

Introduction: A primary goal of the NASA Mars 2020 Perseverance rover mission is to select, acquire, and document a scientifically return-worthy collection of martian samples for return to Earth by future missions [1]. Perseverance is currently exploring Noachian-aged Jezero Crater, once the site of a delta-lake system with a high potential for habitability. Perseverance carries 38 identical sample tubes designed for rock core or regolith, and five "witness tubes" for characterizing contamination from the rover. As of the completion of the Crater Floor Campaign in mid-March, 2022, Perseverance has sealed 10 tubes: 8 rock cores, one tube in which inadvertently no core was acquired but which does include a serendipitous sample of ~5 µmol of ambient atmosphere (Table 1), and one witness tube. Here we provide an overview of the characterization and documentation acquired during each sample collection. The Sampling and Caching Subsystem (SCS) is fully decribed by [2]. The "STOP: List: During mission operations, a standardized set of required activities and observations are undertaken to fully document a sample, once the sampling target has been identified. These activities are called the Standardized Observation Protocol, or STOP list. The STOP list includes imagery at multiple scales along with chemical and mineralogical analyses of the outcrop surface. Because rock surfaces are frequently coated with dust or other materials, an ~1 cm deep and 5 cm diameter Abrasion Target is acquired within a few tens of cm of the sample target within the same lithology (Table 1). In this "sample proxy" patch, high-resolution images and detailed maps of elemental composition, mineralogy and potential organic matter are obtained. After coring, an image is taken of the sample in the tube, the amount of sample is estimated, and the tube is hermetically sealed [2]. Unique serial numbers are readily visible on the tube and seal exteriors to ensure confident identification even decades after acquisition. Sample documentation: Each sample is documented by the following products: Sample Dossier: Contains all observations from the STOP list, along with relevant rover data (e.g., temperatures, rover location, rover arm position and actions, etc). Uploaded to the NASA Planetary Data System (PDS) on a regular cadence, the Sample Dossier primarily consists of pointers to instrument-specific and engineering data products. These data are independently delivered to the PDS, and thus the dossier acts as a "one stop shop" for sample-specific results. Initial Report: A description of each sample in a standardized narrative format is written by the Science Team within three weeks of sample acquisition to capture the reasons for sampling and describe the interpretations available at the time of sampling and the completion of the STOP list. The Initial Report can be thought of as a set of field notes associated with each sample. Initial Reports are archived in the NASA PDS as an element of each Sample Dossier. The first volume of the Mars 2020 Initial Reports has been delivered to the NASA PDS; this volume includes the first four tubes collected during the Crater Floor Campaign: specifically, the Bit Carousel Witness Tube (see [2] for details); and the tubes containing Roubion, Montdenier and Montagnac (Table 1). Like field notes, the Initial Reports do not include extensive assessment and interpretation of the collected samples; these are reported elsewhere. The mineralogy, petrology and geochemistry of the first several samples collected during the Crater Floor Campaign, as well as the stratigraphy of crater floor units, can be found in [3,4]. Implications for Returned Sample Science are provided by [5]; comparisons with martian meteorite lithologies are provided by [6, 7]. [ABSTRACT FROM AUTHOR]

Abstract: Hydrogen gas produced in the subsurface from the hydration of mafic rocks is known to be a major energy source for chemolithotrophic life in extreme environments such as hydrothermal vents. The possibility that in situ anaerobic microorganisms present in the deep subsurface are sustained by low temperature H2-generating water–rock reactions taking place around them is being investigated. Whether the growth and activity of H2-utilizing microbes directly influences aqueous geochemistry, rates of mineral dissolution, and the chemical composition of the alteration products is also being quantitatively evaluated. To explore how microorganisms are affected by water–rock reactions, and how their activity may in turn affect reaction progress, laboratory experiments have been conducted to monitor the growth of a methanogenic Archaea in the presence of H2(g) produced from low temperature water–Fe0–basalt reactions. In these systems, the conversion of Fe(II) to Fe(III) and subsequent hydrolysis of water is responsible for the production of H2(g). To characterize key components of the geochemical system, time series measurements of H2 and CH4 gas concentrations, Fe and Si aqueous concentrations, and spatially resolved synchrotron-based analyses of microscale Fe distribution and speciation were conducted. Culture experiments were compared with an abiotic control to document changes in the geochemistry both in the presence and absence of the methanogen. In the control abiotic batch experiment, H2 was continuously produced, until the headspace became saturated, while in the biotic experiments, microbial consumption of H2 for methanogenesis draws H2 down and produces CH4. Purging the headspace gas reinitiates H2 and CH4 production in abiotic and culture experiments, respectively. Mass balance analysis of the amount of CH4 produced suggests that the total H2 production in microbial experiments does not exceed the abiotic experiment. Soluble Si concentrations, while buffered to relatively constant values, were higher in culture experiments than the abiotic control. Iron(aq) concentrations appear to respond to perturbations of H2 and CH4 gas concentrations in both culture experiments and the abiotic control. A pulse of Fe preceded the rise in either H2 or CH4 production, and as the gas concentrations increased the Fe(aq) decreased. Iron-bearing mineral assemblages change with increasing reaction time and mineral assemblages vary between culture experiments and the abiotic control. These geochemical trends suggest that there are different reaction paths between the culture experiments and the abiotic control. The hydration of mafic rocks is a common geologic reaction and one that has taken place on Earth for the majority of its history and is postulated to occur on Mars. These reactions are important because of their effect on the rheology and geochemistry of the ocean crust. While most often studied at temperatures of ∼250°C, this work suggests that at lower temperatures microorganisms may have a profound effect on what has long been thought to be solely an abiotic reaction, and may produce diagnostic mineral assemblages that will be preserved in the geological record. [Copyright &y& Elsevier]

Before Perseverance, Jezero crater's floor was variably hypothesized to have a lacustrine, lava, volcanic airfall, or aeolian origin. SuperCam observations in the first 286 Mars days on Mars revealed a volcanic and intrusive terrain with compositional and density stratification. The dominant lithology along the traverse is basaltic, with plagioclase enrichment in stratigraphically higher locations. Stratigraphically lower, layered rocks are richer in normative pyroxene. The lowest observed unit has the highest inferred density and is olivine-rich with coarse (1.5 millimeters) euhedral, relatively unweathered grains, suggesting a cumulate origin. This is the first martian cumulate and shows similarities to martian meteorites, which also express olivine disequilibrium. Alteration materials including carbonates, sulfates, perchlorates, hydrated silicates, and iron oxides are pervasive but low in abundance, suggesting relatively brief lacustrine conditions. Orbital observations link the Jezero floor lithology to the broader Nili-Syrtis region, suggesting that density-driven compositional stratification is a regional characteristic.

The iron chemistry of serpentinites and serpentine group minerals is often invoked as a record of the setting and conditions of serpentinization because Fe behaviour is influenced by reaction conditions. Iron can be partitioned into a variety of secondary mineral phases and undergo variable extents of oxidation and/or reduction during serpentinization. This behaviour influences geophysical, geochemical and biological aspects of serpentinizing systems and, more broadly, earth systems. Iron chemistry of serpentinites and serpentines is frequently analysed and reported for single systems. Interpretations of the controls on, and the implications of, Fe behaviour drawn from a single system are often widely extrapolated. There is a wealth of serpentinite/serpentine chemical composition data available in the literature. Consequently, compilation of a database including potential predictors of Fe behaviour and measures of Fe chemistry enables systematic investigation of trends in Fe behaviour across a variety of systems and conditions. The database presented here contains approximately 2000 individual data points including both bulk rock and serpentine mineral geochemical data which are paired whenever possible. Measures of total Fe and Fe oxidation state, which are more limited, are compiled with characteristics of the systems from which they were sampled. Observations of trends in Fe chemistry in serpentinites and serpentines across the variety of geologic systems and parameters will aid in verifying and strengthening interpretations made on the basis of Fe chemistry. This article is part of a discussion meeting issue 'Serpentinite in the Earth system'.