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Abstract
The release of phosphorus (P) from crustal rocks during weathering plays a key role in determining the size of Earth's biosphere, yet the concentration of P in crustal rocks over time remains controversial. Here, we combine spatial, temporal, and chemical measurements of preserved rocks to reconstruct the lithological and chemical evolution of Earth's continental crust. We identify a threefold increase in average crustal P concentrations across the Neoproterozoic-Phanerozoic boundary (600 to 400 million years), showing that preferential biomass burial on shelves acted to progressively concentrate P within continental crust. Rapid compositional change was made possible by massive removal of ancient P-poor rock and deposition of young P-rich sediment during an episode of enhanced global erosion. Subsequent weathering of newly P-rich crust led to increased riverine P fluxes to the ocean. Our results suggest that global erosion coupled to sedimentary P-enrichment forged a markedly nutri-ent-rich crust at the dawn of the Phanerozoic.
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Abstract
The open data movement has brought revolutionary changes to the field of mineralogy. With a growing number of datasets made available through community efforts, researchers are now able to explore new scientific topics such as mineral ecology, mineral evolution and new classification systems. The recent results have shown that the necessary open data coupled with data science skills and expertise in mineralogy will lead to impressive new scientific discoveries. Yet, feedback from researchers also reflects the needs for better FAIRness of open data, that is, findable, accessible, interoperable and reusable for both humans and machines. In this paper, we present our recent work on building the open data service of Mindat, one of the largest mineral databases in the world. In the past years, Mindat has supported numerous scientific studies but a machine interface for data access has never been established. Through the OpenMindat project we have achieved solid progress on two activities: (1) cleanse data and improve data quality, and (2) build a data sharing platform and establish a machine interface for data query and access. We hope OpenMindat will help address the increasing data needs from researchers in mineralogy for an internationally recognized authoritative database that is fully compliant with the FAIR guiding principles and helps accelerate scientific discoveries.
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Abstract
We report the results of observations of p-mode oscillations in the G0 subgiant star HD 35833 in both radial velocities and photometry with NEID and TESS, respectively. We achieve separate, robust detections of the oscillation signal with both instruments (radial velocity amplitude A (RV) = 1.11 +/- 0.09 m s(-1), photometric amplitude A (phot) = 6.42 +/- 0.60 ppm, frequency of maximum power nu(max)=595.71 +/- 17.28 mu Hz, and mode spacing delta nu = 36.65 +/- 0.96 mu Hz) as well as a nondetection in a TESS sector concurrent with the NEID observations. These data shed light on our ability to mitigate the correlated noise impact of oscillations with radial velocities alone and on the robustness of commonly used asteroseismic scaling relations. The NEID data are used to validate models for the attenuation of oscillation signals for exposure times t 4 sigma, hinting at gaps in the underlying physical models.
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Abstract
The Transiting Exoplanet Survey Satellite (TESS) mission detected a companion orbiting TIC 71268730, categorized it as a planet candidate, and designated the system TOI-5375. Our follow-up analysis using radial-velocity data from the Habitable-zone Planet Finder, photometric data from Red Buttes Observatory, and speckle imaging with NN-EXPLORE Exoplanet Stellar Speckle Imager determined that the companion is a very low mass star near the hydrogen-burning mass limit with a mass of 0.080 +/- 0.002M(circle dot) (83.81 +/- 2.10M(J)), a radius of 0.1114(-0.0050)(+0.0048)R(circle dot) (1.0841(0.0487)(0.0467)R(J)), and brightness temperature of 2600 +/- 70 K. This object orbits with a period of 1.721553 +/- 0.000001 days around an early M dwarf star (0.62 +/- 0.016M(circle dot)). TESS photometry shows regular variations in the host star's TESS light curve, which we interpreted as an activity-induced variation of similar to 2%, and used this variability to measure the host star's stellar rotation period of 1.9716(-0.0083)(+0.0080) days. The TOI-5375 system provides tight constraints on stellar models of low-mass stars at the hydrogen-burning limit and adds to the population in this important region.
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Abstract
TOI-2076 b is a sub-Neptune-sized planet (R = 2.39 + 0.10 R-circle plus) that transits a young (204 + 50 MYr) bright (V= 9.2) K-dwarf hosting a system of three transiting planets. Using spectroscopic observations obtained with the NEID spectrograph on the WIYN 3.5 m Telescope, we model the Rossiter-McLaughlin effect of TOI-2076 b, and derive a sky-projected obliquity of lambda = - 3 (-15) (+16) . Using the size of the star (R = 0.775 + 0.015 R-?), and the stellar 16 rotation period (P-rot = 7.27 + 0.23 days), we estimate an obliquity of y =18(-9) (+10) (psi < 34 degrees at 95% confidence), 10 demonstrating that TOI-2076 b is in a well-aligned orbit. Simultaneous diffuser-assisted photometry from the 3.5 m telescope at Apache Point Observatory rules out flares during the transit. TOI-2076 b joins a small but growing sample of young planets in compact multi-planet systems with well-aligned orbits, and is the fourth planet with an age ?300 Myr in a multi-transiting system with an obliquity measurement. The low obliquity of TOI-2076 b and the presence of transit timing variations in the system suggest the TOI-2076 system likely formed via convergent disk migration in an initially well-aligned disk.
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Abstract
Agrowing avenue for determining the prevalence of life beyond Earth is to search for "technosignatures" from extraterrestrial intelligences/agents. Technosignatures require significant energy to be visible across interstellar space and thus intentional signals might be concentrated in frequency, in time, or in space, to be found in mutually obvious places. Therefore, it could be advantageous to search for technosignatures in parts of parameter space that are mutually derivable to an observer on Earth and a distant transmitter. In this work, we used the L-band (1.1-1.9 GHz) receiver on the Robert C. Byrd Green Bank Telescope to perform the first technosignature search presynchronized with exoplanet transits, covering 12 Kepler systems. We used the Breakthrough Listen turboSETI pipeline to flag narrowband hits (similar to 3 Hz) using a maximum drift rate of +/- 614.4 Hz s(-1) and a signal-to-noise threshold of 5-the pipeline returned similar to 3.4 x 10(5) apparently-localized features. Visual inspection by a team of citizen scientists ruled out 99.6% of them. Further analysis found two signals of interest that warrant follow up, but no technosignatures. If the signals of interest are not redetected in future work, it will imply that the 12 targets in the search are not producing transit-aligned signals from 1.1 to 1.9 GHz with transmitter powers >60 times that of the former Arecibo radar. This search debuts a range of innovative technosignature techniques: citizen science vetting of potential signals of interest, a sensitivity-aware search out to extremely high drift rates, a more flexible method of analyzing on-off cadences, and an extremely low signal-to-noise threshold.
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Abstract
The detection of satellites around extrasolar planets, so called exomoons, remains a largely unexplored territory. In this work, we study the potential of detecting these elusive objects from radial velocity monitoring of self-luminous, directly imaged planets. This technique is now possible thanks to the development of dedicated instruments combining the power of high-resolution spectroscopy and high-contrast imaging. First, we demonstrate a sensitivity to satellites with a mass ratio of 1%-4% at separations similar to the Galilean moons from observations of a brown-dwarf companion (HR 7672 B; K (mag) = 13; 0.'' 7 separation) with the Keck Planet Imager and Characterizer (R similar to 35,000 in the K band) at the W. M. Keck Observatory. Current instrumentation is therefore already sensitive to large unresolved satellites that could be forming from gravitational instability akin to binary star formation. Using end-to-end simulations, we then estimate that future instruments such as the Multi-Object Diffraction-limited High-resolution Infrared Spectrograph, planned for the Thirty Meter Telescope, should be sensitive to satellites with mass ratios of similar to 10(-4). Such small moons would likely form in a circumplanetary disk similar to the Jovian satellites in the solar system. Looking for the Rossiter-McLaughlin effect could also be an interesting pathway to detecting the smallest moons on short orbital periods. Future exomoon discoveries will allow precise mass measurements of the substellar companions that they orbit and provide key insight into the formation of exoplanets. They would also help constrain the population of habitable Earth-sized moons orbiting gas giants in the habitable zone of their stars.
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Abstract
Deep extensions of low seismic velocities in the mantle beneath volcanic centers are commonly attributed to high temperatures and have been used as a possible characteristic of hot plumes originating at the core-mantle boundary. To address this issue, we examine the effect of volatiles on melting to determine if regions of low seismic velocities may also be interpreted as regions of melting without elevated temperatures. We find that for the very small amounts of H2O in the oceanic mantle, the effect on solidus temperatures is a reduction of at most similar to 13 degrees C, which can be neglected. In contrast, even the smallest amount of carbonate reduces solidus temperatures more than 300 degrees C at pressures greater than 1.9 GPa. The close match between detailed seismic imaging of the upper boundary of the low-velocity zone on the East Pacific Rise and the sharp temperature decrease for the carbonated lherzolite solidus at similar to 1.9 GPa supports earlier suggestions that the low-velocity zone (similar to 70-150 km depth) is caused by melting due to the presence of carbonate. For locally elevated concentrations of carbonate subducted into the mantle along with oceanic crust, melting of the resulting carbonated lherzolite and carbonated eclogite could also occur at greater depths, possibly into the lower mantle, without elevated temperatures. Thus seismic imaging of deep low-velocity regions may reveal the locations of old subducted crust rather than hot plumes.
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Abstract
Seven particles captured by the Stardust Interstellar Dust Collector and returned to Earth for laboratory analysis have features consistent with an origin in the contemporary interstellar dust stream. More than 50 spacecraft debris particles were also identified. The interstellar dust candidates are readily distinguished from debris impacts on the basis of elemental composition and/or impact trajectory. The seven candidate interstellar particles are diverse in elemental composition, crystal structure, and size. The presence of crystalline grains and multiple iron-bearing phases, including sulfide, in some particles indicates that individual interstellar particles diverge from any one representative model of interstellar dust inferred from astronomical observations and theory.
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Abstract
On the basis of an interstellar dust model compatible with Ulysses and Galileo observations, we calculate and predict the trajectories of interstellar dust (ISD) in the solar system and the distribution of the impact speeds, directions, and flux of ISD particles on the Stardust Interstellar Dust Collector during the two collection periods of the mission. We find that the expected impact velocities are generally low (<10 km s(-1)) for particles with the ratio of the solar radiation pressure force to the solar gravitational force beta > 1, and that some of the particles will impact on the cometary side of the collector. If we assume astronomical silicates for particle material and a density of 2 g cm(-3), and use the Ulysses measurements and the ISD trajectory simulations, we conclude that the total number of (detectable) captured ISD particles may be on the order of 50. In companion papers in this volume, we report the discovery of three interstellar dust candidates in the Stardust aerogel tiles. The impact directions and speeds of these candidates are consistent with those calculated from our ISD propagation model, within the uncertainties of the model and of the observations.
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