Exploring and Validating Exoplanet Atmospheric Retrievals with Solar System Analog Observations

Solar System observations that serve as analogs for exoplanet remote sensing data can provide important opportunities to validate ideas and models related to exoplanet environments. Critically, and unlike true exoplanet observations, Solar System analog data benefit from available high-quality ground- or orbiter-derived "truth" constraints that enable strong validations of exoplanet data interpretation tools. In this work, we first present a versatile atmospheric retrieval suite, capable of application to reflected light, thermal emission, and transmission observations. The tool -- dubbed rfast -- is designed, in part, to enable exoplanet mission concept feasibility studies. Following model validation, the retrieval tool is applied to a range of Solar System analog observations for exoplanet environments. Retrieval studies using Earth reflected light observations from NASA's EPOXI mission provide a key proof-of-concept for under-development exo-Earth direct imaging concept missions. Inverse modeling applied to an infrared spectrum of Earth from the Mars Global Surveyor Thermal Emission Spectrometer achieves good constraints on atmospheric gases, including many biosignature gases. Finally, retrieval analysis applied to a transit spectrum of Titan derived from the Cassini Visual and Infrared Mapping Spectrometer provides a proof-of-concept for interpreting more feature-rich transiting exoplanet observations from NASA's James Webb Space Telescope (JWST). In the future, Solar System analog observations for exoplanets could be used to verify exoplanet models and parameterizations, and future exoplanet analog observations of any Solar System worlds from planetary science missions should be encouraged.Comment: submitted to PSJ; community comments and feedback welcome

L'abri sous roche Cadet 3 (Marie-Galante) : un gisement à accumulations de faune et à vestiges archéologiques

International audienceA 2 m² recognition test pit was undertaken in 2004 in this small rock shelter, immediately nearby Grotte Cadet 2. The excavation revealed a 1,20 m thick sedimentary infilling. The sediments blocked behind an accumulation of blocks at the cave entrance accumulated since the late Pleistocene and during the Holocene. The lower part of the infilling is composed of phosphate deposits rich in vertebrate faunal remains, land snails and land crabs. The basis of this level was dated to about 13 800 BC. The upper part of the sequence yielded traces of a late Neoindian occupation dated to about AD 1000 and of subsequent historical remains. About fifty taxa were identified. The stratigraphic sequence therefore reveals the history of the animal peopling and subsequent anthropization of the Guadeloupean environments. The deepest layers have yielded a high diversity of Chiroptera, avian, saurian and amphibian fauna. The part of native vertebrate species decreases progressively: this fact probably reflects an direct (introduction, predation) or indirect (ecosystem disturbance) anthropization of the environments. On the other hand, the part of land snails and land crabs grows substantially. Finally, the upper levels, related to post-Columbian deposits, illustrate a rather sudden stop in the cavity's use by the small native insular fauna and a dramatic drop in vertebrates' diversity. The old world domestic taxa then compose most of the taphocenose of the shelter. The faunal associations enable to partially infer the composition of the surrounding environments during each period. However this reading is made complex given the multiplicity of agents responsible in these accumulations, a point which is discussed in this paper. Finally this assemblage offers a remarquable stratified series, quite new for the Lesser Antilles islands.Ce petit abri sous-roche, immédiatement voisin de la Grotte Cadet 2, a fait l'objet d'un sondage de reconnaissance de 2 m2. L'investigation a révélé un remplissage d'une épaisseur de 1,20 m. Les sédiments piégés en arrière de blocs effondrés à l'entrée de la cavité se sont accumulés depuis la fin du Pléistocène et au cours de l'Holocène. La partie inférieure du remplissage est constituée de dépôts phosphatés riches en restes de faune vertébrée, de crustacés et de gastéropodes terrestres. La base a été datée autour de 13 800 av. J.-C. La partie supérieure de la série a livré les traces d'une occupation du Néoindien récent datée autour de l'an 1000, puis de vestiges d'époque historique. Près d'une cinquantaine de taxons ont été identifiés. La séquence stratigraphique révèle l'histoire du peuplement animal et, en conséquence, de l'anthropisation des milieux. Les couches profondes ont fourni une grande diversité de chiroptères, d'oiseaux, de squamates et d'amphibiens. La part des espèces natives de vertébrés diminue au fur et à mesure de l'édification des dépôts, ce qui est probablement dû à une anthropisation des milieux, directe (introduction, prédation) ou indirecte (perturbations des ecosystèmes), alors que les crustacés et les gastéropodes terrestres prennent une part de plus en plus conséquente. Enfin, les couches superficielles, correspondant à des niveaux post-colombiens, se caractérisent par une disparition brutale de l'utilisation de la cavité par les petites faunes natives de l'île et une chute drastique de la biodiversité des vertébrés. Les animaux domestiques constituent alors l'essentiel de la taphocénose de l'abri. Les associations fauniques permettent d'inférer en partie la composition des milieux écologiques environnants au cours de chaque période. Cependant la multiplicité des agents accumulateurs potentiels complique cette lecture et est discutée dans cet article. Enfin, cet assemblage permet de proposer une série faunique stratifiée remarquable pour les Petites Antilles

Bioverse: The Habitable Zone Inner Edge Discontinuity as an Imprint of Runaway Greenhouse Climates on Exoplanet Demographics

Long-term magma ocean phases on rocky exoplanets orbiting closer to their star than the runaway greenhouse threshold - the inner edge of the classical habitable zone - may offer insights into the physical and chemical processes that distinguish potentially habitable worlds from others. Thermal stratification of runaway planets is expected to significantly inflate their atmospheres, potentially providing observational access to the runaway greenhouse transition in the form of a "habitable zone inner edge discontinuity" in radius-density space. Here, we use Bioverse, a statistical framework combining contextual information from the overall planet population with a survey simulator, to assess the ability of ground- and space-based telescopes to test this hypothesis. We find that the demographic imprint of the runaway greenhouse transition is likely detectable with high-precision transit photometry for sample sizes $\gtrsim 100$ planets if at least ~10 % of those orbiting closer than the habitable zone inner edge harbor runaway climates. Our survey simulations suggest that in the near future, ESA's PLATO mission will be the most promising survey to probe the habitable zone inner edge discontinuity. We determine survey strategies that maximize the diagnostic power of the obtained data and identify as key mission design drivers: 1. A follow-up campaign of planetary mass measurements and 2. The fraction of low-mass stars in the target sample. Observational constraints on the runaway greenhouse transition will provide crucial insights into the distribution of atmospheric volatiles among rocky exoplanets, which may help to identify the nearest potentially habitable worlds.Comment: Accepted for publication in The Planetary Science Journal. For a video abstract, see https://youtu.be/acgKcdTTv9c. 29 pages, 12 figures, 1 table. All source code is available at https://github.com/matiscke/hz-inner-edge-discontinuit

Géoarchéologie fluviale

Géoarchéologie fluvial

Dynamic centriolar localization of Polo and Centrobin in early mitosis primes centrosome asymmetry

Centrosomes, the main microtubule organizing centers (MTOCs) of metazoan cells, contain an older "mother" and a younger "daughter" centriole. Stem cells either inherit the mother or daughter-centriole-containing centrosome, providing a possible mechanism for biased delivery of cell fate determinants. However, the mechanisms regulating centrosome asymmetry and biased centrosome segregation are unclear. Using 3D-structured illumination microscopy (3D-SIM) and live-cell imaging, we show in fly neural stem cells (neuroblasts) that the mitotic kinase Polo and its centriolar protein substrate Centrobin (Cnb) accumulate on the daughter centriole during mitosis, thereby generating molecularly distinct mother and daughter centrioles before interphase. Cnb's asymmetric localization, potentially involving a direct relocalization mechanism, is regulated by Polo-mediated phosphorylation, whereas Polo's daughter centriole enrichment requires both Wdr62 and Cnb. Based on optogenetic protein mislocalization experiments, we propose that the establishment of centriole asymmetry in mitosis primes biased interphase MTOC activity, necessary for correct spindle orientation

Mass and pressure constraints on galaxy clusters from interferometric SZ observations

Following on our previous study of an analytic parametric model to describe the baryonic and dark matter distributions in clusters of galaxies with spherical symmetry, we perform an SZ analysis of a set of simulated clusters and present their mass and pressure profiles. The simulated clusters span a wide range in mass, 2.0 x 10^14 Msun < M200 < 1.0 x 10^15Msun, and observations with the Arcminute Microkelvin Imager (AMI) are simulated through their Sunyaev- Zel'dovich (SZ) effect. We assume that the dark matter density follows a Navarro, Frenk and White (NFW) profile and that the gas pressure is described by a generalised NFW (GNFW) profile. By numerically exploring the probability distributions of the cluster parameters given simulated interferometric SZ data in the context of Bayesian methods, we investigate the capability of this model and analysis technique to return the simulated clusters input quantities. We show that considering the mass and redshift dependency of the cluster halo concentration parameter is crucial in obtaining an unbiased cluster mass estimate and hence deriving the radial profiles of the enclosed total mass and the gas pressure out to r200.Comment: 5 pages, 2 tables, 3 figure

The long-term evolution of the atmosphere of Venus: processes and feedback mechanisms

In this chapter, we focus on the long-term evolution of the atmosphere of Venus, and how it has been affected by interior/exterior cycles. The formation and evolution of Venus's atmosphere, leading to the present-day surface conditions, remain hotly debated and involve questions that tie into many disciplines. Here, we explore the mechanisms that shaped the evolution of the atmosphere, starting with the volatile sources and sinks. Going from the deep interior to the top of the atmosphere, we describe fundamental processes such as volcanic outgassing, surface-atmosphere interactions, and atmosphere escape. Furthermore, we address more complex aspects of the history of Venus, including the role of meteoritic impacts, how magnetic field generation is tied into long-term evolution, and the implications of feedback cycles for atmospheric evolution. Finally, we highlight three plausible end-member evolutionary pathways that Venus might have followed, from the accretion to its present-day state, based on current modeling and observations. In a first scenario, the planet was desiccated early-on, during the magma ocean phase, by atmospheric escape. In a second scenario, Venus could have harbored surface liquid water for long periods of time, until its temperate climate was destabilized and it entered a runaway greenhouse phase. In a third scenario, Venus's inefficient outgassing could have kept water inside the planet, where hydrogen was trapped in the core and the mantle was oxidized. We discuss existing evidence and future observations/missions needed to refine our understanding of the planet's history and of the complex feedback cycles between the interior, surface, and atmosphere that operate in the past, present or future of Venus

The Long-Term Evolution of the Atmosphere of Venus: Processes and Feedback Mechanisms: Interior-Exterior Exchanges

This work reviews the long-term evolution of the atmosphere of Venus, and modulation of its composition by interior/exterior cycling. The formation and evolution of Venus’s atmosphere, leading to contemporary surface conditions, remain hotly debated topics, and involve questions that tie into many disciplines. We explore these various inter-related mechanisms which shaped the evolution of the atmosphere, starting with the volatile sources and sinks. Going from the deep interior to the top of the atmosphere, we describe volcanic outgassing, surface-atmosphere interactions, and atmosphere escape. Furthermore, we address more complex aspects of the history of Venus, including the role of Late Accretion impacts, how magnetic field generation is tied into long-term evolution, and the implications of geochemical and geodynamical feedback cycles for atmospheric evolution. We highlight plausible end-member evolutionary pathways that Venus could have followed, from accretion to its present-day state, based on modeling and observations. In a first scenario, the planet was desiccated by atmospheric escape during the magma ocean phase. In a second scenario, Venus could have harbored surface liquid water for long periods of time, until its temperate climate was destabilized and it entered a runaway greenhouse phase. In a third scenario, Venus’s inefficient outgassing could have kept water inside the planet, where hydrogen was trapped in the core and the mantle was oxidized. We discuss existing evidence and future observations/missions required to refine our understanding of the planet’s history and of the complex feedback cycles between the interior, surface, and atmosphere that have been operating in the past, present or future of Venus

Mussel as a Tool to Define Continental Watershed Quality

Bivalves appear as relevant sentinel species in aquatic ecotoxicology and water quality assessment. This is particularly true in marine ecosystems. In fact, several biomonitoring frameworks in the world used mollusks since several decades on the base of contaminant accumulation (Mussel Watch, ROCCH) and/or biological responses called biomarker (OSPAR) measurements. In freshwater systems, zebra and quagga mussels could represent alternative sentinels, which could be seen as the counterparts of mussel marine species. This chapter presents original studies and projects underlying the interest of these freshwater mussels for water quality monitoring based on contaminant accumulation and biomarker development measurements. These sentinel species could be used as a tool for chemical/biological monitoring of biota under the European water framework directive and for the development of effect-based monitoring tools