scholarly journals Hidden Water in Magma Ocean Exoplanets

2021 ◽  
Vol 922 (1) ◽  
pp. L4
Author(s):  
Caroline Dorn ◽  
Tim Lichtenberg
Keyword(s):  
Bulk Composition ◽  
Population Level ◽  
Experimental Petrology ◽  
Bulk Water ◽  
Magma Ocean ◽  
Fundamental Properties ◽  
Order Of Magnitude ◽  
Magma Oceans ◽  
Current Accuracy ◽  
Water In Magma

Abstract We demonstrate that the deep volatile storage capacity of magma oceans has significant implications for the bulk composition, interior, and climate state inferred from exoplanet mass and radius data. Experimental petrology provides the fundamental properties of the ability of water and melt to mix. So far, these data have been largely neglected for exoplanet mass–radius modeling. Here we present an advanced interior model for water-rich rocky exoplanets. The new model allows us to test the effects of rock melting and the redistribution of water between magma ocean and atmosphere on calculated planet radii. Models with and without rock melting and water partitioning lead to deviations in planet radius of up to 16% for a fixed bulk composition and planet mass. This is within the current accuracy limits for individual systems and statistically testable on a population level. Unrecognized mantle melting and volatile redistribution in retrievals may thus underestimate the inferred planetary bulk water content by up to 1 order of magnitude.

scholarly journals Mutability of demographic noise in microbial range expansions

2021 ◽  
Author(s):  
QinQin Yu ◽  
Matti Gralka ◽  
Marie-Cécilia Duvernoy ◽  
Megan Sousa ◽  
Arbel Harpak ◽  
...  
Keyword(s):  
Gene Deletion ◽  
Genetic Manipulation ◽  
Single Gene ◽  
Population Level ◽  
Growth Conditions ◽  
Establishment Probability ◽  
In The Wild ◽  
Order Of Magnitude ◽  
Demographic Noise ◽  
Single Gene Deletion

AbstractDemographic noise, the change in the composition of a population due to random birth and death events, is an important driving force in evolution because it reduces the efficacy of natural selection. Demographic noise is typically thought to be set by the population size and the environment, but recent experiments with microbial range expansions have revealed substantial strain-level differences in demographic noise under the same growth conditions. Many genetic and phenotypic differences exist between strains; to what extent do single mutations change the strength of demographic noise? To investigate this question, we developed a high-throughput method for measuring demographic noise in colonies without the need for genetic manipulation. By applying this method to 191 randomly-selected single gene deletion strains from the E. coli Keio collection, we find that a typical single gene deletion mutation decreases demographic noise by 8% (maximal decrease: 81%). We find that the strength of demographic noise is an emergent trait at the population level that can be predicted by colony-level traits but not cell-level traits. The observed differences in demographic noise from single gene deletions can increase the establishment probability of beneficial mutations by almost an order of magnitude (compared to in the wild type). Our results show that single mutations can substantially alter adaptation through their effects on demographic noise and suggest that demographic noise can be an evolvable trait of a population.

scholarly journals Transcribed enhancers in the human brain identify novel disease risk mechanisms

2021 ◽  
Author(s):  
Pengfei Dong ◽  
Gabriel E. Hoffman ◽  
Pasha Apontes ◽  
Jaroslav Bendl ◽  
Samir Rahman ◽  
...  
Keyword(s):  
Human Brain ◽  
Disease Risk ◽  
Association Studies ◽  
Population Level ◽  
Cell Type ◽  
Level Variation ◽  
Functional Interpretation ◽  
Neuropsychiatric Diseases ◽  
Order Of Magnitude ◽  
Cell Type Specific

Enhancer RNAs (eRNAs) constitute an important tissue- and cell-type-specific layer of the regulome. Identification of risk variants for neuropsychiatric diseases within enhancers underscores the importance of understanding the population-level variation of eRNAs in the human brain. We jointly analyzed cell type-specific transcriptome and regulome data to identify 30,795 neuronal and 23,265 non-neuronal eRNAs, expanding the catalog of known human brain eRNAs by an order of magnitude. Examination of the population-level variation of the transcriptome and regulome in 1,382 brain samples identified reproducible changes affecting cis- and trans-co-regulation of eRNA-gene modules in schizophrenia. We show that 13% of schizophrenia heritability is jointly mediated in cis by brain gene and eRNA expression. Inclusion of eRNAs in transcriptome-wide association studies facilitated fine-mapping and functional interpretation of disease loci. Overall, our study characterizes the eRNA-gene regulome and genetic mechanisms in the human cortex in both healthy and disease states.

Coupled models of magma oceans and their primordial atmospheres: volatile speciation, cooling history, and impact of condensables

2021 ◽  
Author(s):  
Tim Lichtenberg ◽  
Robert J. Graham ◽  
Ryan Boukrouche ◽  
Raymond T. Pierrehumbert
Keyword(s):  
Extrasolar Planets ◽  
Initial Distribution ◽  
Magma Ocean ◽  
Coupled Models ◽  
Time Resolved ◽  
Planetary Evolution ◽  
Sensitive Dependence ◽  
History Of ◽  
Magma Oceans ◽  
Rocky Planets

<p>The earliest atmospheres of rocky planets originate from extensive volatile release during magma ocean epochs that occur during assembly of the planet. These establish the initial distribution of the major volatile elements between different chemical reservoirs that subsequently evolve via geological cycles. Current theoretical techniques are limited in exploring the anticipated range of compositional and thermal scenarios of early planetary evolution. However, these are of prime importance to aid astronomical inferences on the environmental context and geological history of extrasolar planets. In order to advance the potential synergies between exoplanet observations and inferrences on the earliest history and climate state of the solar system terrestial planets, I will present a novel numerical framework that links an evolutionary, vertically-resolved model of the planetary silicate mantle with a radiative-convective model of the atmosphere. Numerical simulations using this framework illustrate the sensitive dependence of mantle crystallization and atmosphere build-up on volatile speciation and predict variations in atmospheric spectra with planet composition that may be detectable with future observations of exoplanets. Magma ocean thermal sequences fall into three general classes of primary atmospheric volatile with increasing cooling timescale: CO, N<sub>2</sub>, and O<sub>2</sub> with minimal effect on heat flux, H<sub>2</sub>O, CO<sub>2</sub>, and CH<sub>4</sub> with intermediate influence, and H<sub>2</sub> with several orders of magnitude increase in solidification time and atmosphere vertical stratification. In addition to these time-resolved results, I will present a novel formulation and application of a multi-species moist-adiabat for condensable-rich magma ocean and archean earth analog atmospheres, and outline how the cooling of such atmospheres can lead to exotic climate states that provide testable predictions for terrestrial exoplanets.</p>

Albatrosses bathe before departing on a foraging trip: implications for risk assessments and marine spatial planning

2017 ◽  
Vol 28 (2) ◽  
pp. 208-215 ◽  
Author(s):  
JOSÉ P. GRANADEIRO ◽  
LETIZIA CAMPIONI ◽  
PAULO CATRY
Keyword(s):  
Spatial Planning ◽  
Population Level ◽  
Sea Surface ◽  
Risk Assessments ◽  
Marine Spatial Planning ◽  
Large Numbers ◽  
Highly Sensitive ◽  
Order Of Magnitude ◽  
Thalassarche Melanophris ◽  
Marine Areas

SummaryTracking studies of seabirds have generally focused in identifying areas used for foraging, in the hope of highlighting regions of energy transfer which may be important for seabird and general ecosystem conservation and special management. However, some sea areas may serve functions other than providing nutritional resources, which may be equally relevant, particularly if used by large numbers of individuals. In this paper, based on a study of 4 breeding colonies in the Falkland Islands and on 314 individuals tracked, we show that virtually all (97.8%) black-browed albatrosses Thalassarche melanophris (BBA) bathe in the close vicinity of the colony, remaining in the area for nearly an hour, before departing on a foraging trip. This compares with only 20 to 40% of the individuals landing close to the colony at the end of a foraging trip. The observed utilization of marine areas by BBA in a radius of 1 to 5 km around the nesting colony is one order of magnitude higher than elsewhere, including foraging hotspots. Clearly, even long-range flying birds such as albatrosses can make an intensive use of the sea-surface in the immediate vicinity of the colonies, and therefore any threats to seabirds in these areas (disturbance, pollutants, collision with artificial structures and light attraction) can potentially have a major impact at the population level. As such, the close neighbourhood of seabird colonies are potentially highly sensitive areas, and this needs to be taken into account when carrying out risk assessments or during marine spatial planning exercises.

Steam Atmospheres and Magma Oceans on Planets

2020 ◽  
Author(s):  
Keiko Hamano
Keyword(s):  
Feedback Loop ◽  
Radiative Energy ◽  
Terrestrial Planets ◽  
Magma Ocean ◽  
Planetary Body ◽  
Oxidation Of H2 ◽  
Giant Impacts ◽  
Magma Oceans ◽  
Greenhouse Effects ◽  
Insight Into

A magma ocean is a global layer of partially or fully molten rocks. Significant melting of terrestrial planets likely occurs due to heat release during planetary accretion, such as decay heat of short-lived radionuclides, impact energy released by continuous planetesimal accretion, and energetic impacts among planetary-sized bodies (giant impacts). Over a magma ocean, all water, which is released upon impact or degassed from the interior, exists as superheated vapor, forming a water-dominated, steam atmosphere. A magma ocean extending to the surface is expected to interact with the overlying steam atmosphere through material and heat exchange. Impact degassing of water starts when the size of a planetary body becomes larger than Earth’s moon or Mars. The degassed water could build up and form a steam atmosphere on protoplanets growing by planetesimal accretion. The atmosphere has a role in preventing accretion energy supplied by planetesimals from escaping, leading to the formation of a magma ocean. Once a magma ocean forms, part of the steam atmosphere would start to dissolve into the surface magma due to the high solubility of water into silicate melt. Theoretical studies indicated that as long as the magma ocean is present, a negative feedback loop can operate to regulate the amount of the steam atmosphere and to stabilize the surface temperature so that a radiative energy balance is achieved. Protoplanets can also accrete the surrounding H2-rich disk gas. Water could be produced by oxidation of H2 by ferrous iron in the magma. The atmosphere and water on protoplanets could be a mixture of outgassed and disk-gas components. Planets formed by giant impact would experience a global melting on a short timescale. A steam atmosphere could grow by later outgassing from the interior. Its thermal blanketing and greenhouse effects are of great importance in controlling the cooling rate of the magma ocean. Due to the presence of a runaway greenhouse threshold, the crystallization timescale and water budget of terrestrial planets can depend on the orbital distance from the host star. The terrestrial planets in our solar system essentially have no direct record of their earliest history, whereas observations of young terrestrial exoplanets may provide us some insight into what early terrestrial planets and their atmosphere are like. Evolution of protoplanets in the framework of pebble accretion remains unexplored.

Implications of magma oceans for astrophysical observations: mass-radius and atmospheric composition

2020 ◽  
Author(s):  
Dan J. Bower ◽  
Daniel Kitzmann ◽  
Aaron Wolf ◽  
Patrick Sanan ◽  
Caroline Dorn ◽  
...  
Keyword(s):  
Building Blocks ◽  
Atmospheric Composition ◽  
Terrestrial Planets ◽  
Iron Core ◽  
Magma Ocean ◽  
Static Structure ◽  
Emission Data ◽  
Modelling Framework ◽  
Magma Oceans ◽  
Structure Calculations

<div> <div> <div> <p>The earliest secondary atmosphere of a rocky planet originates from extensive volatile release during one or more magma ocean epochs that occur during and after the assembly of the planet. Magma oceans set the stage for the long-term evolution of terrestrial planets by establishing the major chemical reservoirs of the iron core and silicate mantle, chemical stratification within the mantle, and outgassed atmosphere. Furthermore, current and future exoplanet observations will favour the detection and characterisation of hot and warm planets, potentially with large outgassed atmospheres. In this study, we highlight the potential to combine models of coupled interior–atmosphere evolution with static structure calculations and modelled atmospheric spectra (transmission and emission). By combining these components in a common modelling framework, we acknowledge planets as dynamic entities and leverage their evolution to bridge planet formation, interior-atmosphere interaction, and observations.</p> <p>An interior–atmosphere model is combined with static structure calculations to track the evolving radius of a hot rocky mantle that is outgassing volatiles. We consider oxidised species CO2 and H2O and generate synthetic emission and transmission spectra for CO2 and H2O dominated atmospheres. Atmospheres dominated by CO2 suppress the outgassing of H2O to a greater extent than previously realised, since previous studies have applied an erroneous relationship between volatile mass and partial pressure. Furthermore, formation of a lid at the surface can tie the outgassing of H2O to the efficiency of heat transport through the lid, rather than the radiative timescale of the atmosphere. We extend this work to explore the speciation of a primary atmosphere that is constrained using meteoritic materials as proxies for the planetary building blocks, and find that a range of reducing and oxidising atmospheres are possible.</p> </div> </div> </div><div> <div> <div> <p>Our results demonstrate that a hot molten planet can have a radius several percent larger (about 5%, assuming Earth-like core size) than its equivalent solid counterpart, which may explain the larger radii of some close-in exoplanets. Outgassing of a low molar mass species (such as H2O, compared to CO2) can combat the continual contraction of a planetary mantle and even marginally increase the planetary radius. We further use our models to generate synthetic transmission and emission data to aid in the detection and characterisation of rocky planets via transits and secondary eclipses. Atmospheres of terrestrial planets around M-stars that are dominated by CO2 versus H2O could be distinguished by future observing facilities that have extended wavelength coverage (e.g., JWST). Incomplete magma ocean crystallisation, as may be the case for close-in terrestrial planets, or full or part retention of an early outgassed atmosphere, should be considered in the interpretation of observational data from current and future observing facilities.</p> </div> </div> </div>

Characteristics of an hybrid atmosphere with disk-captured and degassing contributions over a rocky planet’s magma ocean. A modeling approach.

2020 ◽  
Author(s):  
Athanasia Nikolaou ◽  
Lorenzo Mugnai ◽  
Oliver Herbort ◽  
Enzo Pascale ◽  
Peter Woitke
Keyword(s):  
Thermal Evolution ◽  
Chemical Characterization ◽  
Protoplanetary Disk ◽  
International Institute ◽  
Atmospheric Conditions ◽  
Magma Ocean ◽  
Silicate Mineral ◽  
Chemical Abundances ◽  
Magma Oceans ◽  
The University

<p>Motivation:<br />   Early during their formation the planets capture an amount of atmosphere from the protoplanetary disk (Ikoma et al. 2018, Odert et al. 2018, Lammer et al. 2020, Kimura and Ikoma 2020). An additional proportion of their atmosphere is provided during the magma ocean stage by interior degassing. The latter mechanism is assumed to be the main provider of the final atmospheric mass. Its composition is compromised by the source silicate mineral and its chemical characterization (Gaillard and Scaillet 2014, Herbort et al. 2020).<br />   Numerous studies support the degassing of the oxidized gas species H<sub>2</sub>O and CO<sub>2</sub> as main contributions from the magma ocean phase (Abe and Matsui 1988, Abe 1993, Elkins-Tanton 2008, Schaefer et al. 2012, Lebrun et al. 2013, Lupu et al. 2014, Gaillard and Scaillet 2014, Salvador et al. 2017, Nikolaou et al. 2019). Previous work has also shown that H<sub>2</sub>O, in particular, plays a crucial role (Hamano et al. 2013, Katyal et al. 2019, Turbet et al. 2019) in thermal blanketing. H<sub>2</sub>O possibly leads to “long-term” (Hamano et al 2013) or “conditionally continuous” (Nikolaou et al. 2019) magma oceans that effectively cease to cool. Water also ties directly to the availability of hydrogen that drives hydrodynamic escape (Airapetian et al. 2017, Lammer et al. 2018). CO<sub>2 </sub>factors into both above processes, as well (Wordsworth and Pierrehumbert 2013, Odert et al. 2018). Constraining the H<sub>2</sub>O and CO<sub>2</sub> abundances early after formation is indispensible to the planet’s thermal evolution and extensive modeling effort has been devoted to it. Their constraint would in particular help revisit which magma ocean types among transient-conditionally continuous-permanent (Nikolaou et al. 2019) are detectable in future exoplanetary missions (ARIEL, Tinetti et al. 2018; PLATO, Rauer et al. 2014).<br /> </p> <p>Method:<br />   In this work we focus on the combination of degassed and disk-captured atmosphere under the assumption of chemical equilibrium. Using simulations from the 1D Convective Ocean of Magma Radiative Atmosphere and Degassing model (Nikolaou et al. 2019) we obtain the thermal evolution and degassing tracks of a rocky planet. In order to evaluate the chemical abundances under equilibrium conditions we employ the thermodynamical model GGchem (Woitke et al. 2018).<br />   We explore the atmospheric conditions during the lifetime of a magma ocean under varying mineral compositions and protoplanetary disk contributions. We discuss the results in the context of the likely magma ocean types.<br /> <br />A.N. and P.W. wish to thank the Erwin Schrödinger International Institute for Mathematics and Physics (ESI) of the University of Vienna, Thematic Programme on “Astrophysical Origins: Pathways from Star Formation to Habitable Planets” 2019, which enabled this collaboration.</p>

scholarly journals Revised mass-radius relationships for water-rich rocky planets more irradiated than the runaway greenhouse limit

2020 ◽  
Vol 638 ◽  
pp. A41 ◽  
Author(s):  
Martin Turbet ◽  
Emeline Bolmont ◽  
David Ehrenreich ◽  
Pierre Gratier ◽  
Jérémy Leconte ◽  
...  
Keyword(s):  
Water Content ◽  
Climate Model ◽  
Bulk Composition ◽  
Order Effect ◽  
Bulk Water ◽  
Density Estimates ◽  
Condensed Form ◽  
Theoretical Mass ◽  
Solid Form ◽  
Rocky Planets

Mass-radius relationships for water-rich rocky planets are usually calculated assuming most water is present in condensed (either liquid or solid) form. Planet density estimates are then compared to these mass-radius relationships, even when these planets are more irradiated than the runaway greenhouse irradiation limit (around 1.1 times the insolation at Earth for planets orbiting a Sun-like star), for which water has been shown to be unstable in condensed form and would instead form a thick H2O-dominated atmosphere. Here we use a 1-D radiative-convective inverse version of the LMD generic numerical climate model to derive new theoretical mass-radius relationships appropriate for water-rich rocky planets that are more irradiated than the runaway greenhouse irradiation limit, meaning planets endowed with a steam, water-dominated atmosphere. As a result of the runaway greenhouse radius inflation effect introduced in previous work, these new mass-radius relationships significantly differ from those traditionally used in the literature. For a given water-to-rock mass ratio, these new mass-radius relationships lead to planet bulk densities much lower than calculated when water is assumed to be in condensed form. In other words, using traditional mass-radius relationships for planets that are more irradiated than the runaway greenhouse irradiation limit tends to dramatically overestimate -possibly by several orders of magnitude- their bulk water content. In particular, this result applies to TRAPPIST-1 b, c, and d, which can accommodate a water mass fraction of at most 2, 0.3 and 0.08%, respectively, assuming planetary core with a terrestrial composition. In addition, we show that significant changes of mass-radius relationships (between planets less and more irradiated than the runaway greenhouse limit) can be used to remove bulk composition degeneracies in multiplanetary systems such as TRAPPIST-1. Broadly speaking, our results demonstrate that non-H2/He-dominated atmospheres can have a first-order effect on the mass-radius relationships, even for rocky planets receiving moderate irradiation. Finally, we provide an empirical formula for the H2O steam atmosphere thickness as a function of planet core gravity and radius, water content, and irradiation. This formula can easily be used to construct mass-radius relationships for any water-rich, rocky planet (i.e., with any kind of interior composition ranging from pure iron to pure silicate) more irradiated than the runaway greenhouse irradiation threshold.

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