Pour voir les autres types de publications sur ce sujet consultez le lien suivant : Primordial atmosphere.
Articles de revues sur le sujet « Primordial atmosphere »
Créez une référence correcte selon les styles APA, MLA, Chicago, Harvard et plusieurs autres
Consultez les 50 meilleurs articles de revues pour votre recherche sur le sujet « Primordial atmosphere ».
À côté de chaque source dans la liste de références il y a un bouton « Ajouter à la bibliographie ». Cliquez sur ce bouton, et nous générerons automatiquement la référence bibliographique pour la source choisie selon votre style de citation préféré : APA, MLA, Harvard, Vancouver, Chicago, etc.
Vous pouvez aussi télécharger le texte intégral de la publication scolaire au format pdf et consulter son résumé en ligne lorsque ces informations sont inclues dans les métadonnées.
Parcourez les articles de revues sur diverses disciplines et organisez correctement votre bibliographie.
1
Ragossnig, Florian, Alexander Stökl, Ernst Dorfi, Colin P. Johnstone, Daniel Steiner et Manuel Güdel. « Interaction of infalling solid bodies with primordial atmospheres of disk-embedded planets ». Astronomy & ; Astrophysics 618 (octobre 2018) : A19. http://dx.doi.org/10.1051/0004-6361/201832681.
Texte intégralRésumé :
Context. Planets that form early enough to be embedded in the circumstellar gas disk accumulate thick atmospheres of nebular gas. Models of these atmospheres need to specify the surface luminosity (i.e. energy loss rate) of the planet. This luminosity is usually associated with a continuous inflow of solid bodies, where the gravitational energy released from these bodies is the source of energy. However, if these bodies release energy in the atmosphere instead of at the surface, this assumption might not be justified. Aims. Our aim is to explore the interactions of infalling planetesimals with primordial atmospheres at an embedded phase of evolution. We investigate effects of atmospheric interaction on the planetesimals (mass loss) and the atmosphere (heating/cooling). Methods. We used atmospheric parameters from a snapshot of time-dependent evolution simulations for embedded atmospheres and simulated purely radial, infall events of siliceous planetesimals in a 1D, explicit code. We implemented energy transfer between friction, radiation transfer by the atmosphere and the body, and thermal ablation; this gives us the possibility to examine the effects on the planetesimals and the atmosphere. Results. We find that a significant amount of gravitational energy is indeed dissipated into the atmosphere, especially for larger planetary cores, which consequently cannot contribute to the atmospheric planetary luminosity. Furthermore, we examine that planetesimal infall events for cores, MC > 2M⊕, which actually result in a local cooling of the atmosphere; this is totally in contradiction with the classical model.
2
Chance, Quadry, Sarah Ballard et Keivan Stassun. « Signatures of Impact-driven Atmospheric Loss in Large Ensembles of Exoplanets ». Astrophysical Journal 937, no 1 (1 septembre 2022) : 39. http://dx.doi.org/10.3847/1538-4357/ac8a97.
Texte intégralRésumé :
Abstract The results of large-scale exoplanet transit surveys indicate that the distribution of small planet radii is likely sculpted by atmospheric loss. Several possible physical mechanisms exist for this loss of primordial atmospheres, each of which produces a different set of observational signatures. In this study, we investigate the impact-driven mode of atmosphere loss via N-body simulations. We compare the results from giant impacts, at a demographic level, to results from another commonly invoked method of atmosphere loss, photoevaporation. Applying two different loss prescriptions to the same sets of planets, we then examine the resulting distributions of planets with retained primordial atmospheres. As a result of this comparison, we identify two new pathways toward discerning the dominant atmospheric-loss mechanism at work. Both of these pathways involve using transit multiplicity as a diagnostic, in examining the results of follow-up atmospheric and radial velocity surveys.
3
Kimura, Tadahiro, et Masahiro Ikoma. « Formation of aqua planets with water of nebular origin : effects of water enrichment on the structure and mass of captured atmospheres of terrestrial planets ». Monthly Notices of the Royal Astronomical Society 496, no 3 (22 juin 2020) : 3755–66. http://dx.doi.org/10.1093/mnras/staa1778.
Texte intégralRésumé :
ABSTRACT Recent detection of exoplanets with Earth-like insolation attracts growing interest in how common Earth-like aqua planets are beyond the Solar system. While terrestrial planets are often assumed to capture icy or water-rich planetesimals, a primordial atmosphere of nebular origin itself can produce water through oxidation of the atmospheric hydrogen with oxidizing minerals from incoming planetesimals or the magma ocean. Thermodynamically, normal oxygen buffers produce water comparable in mole number equal to or more than hydrogen. Thus, the primordial atmosphere would likely be highly enriched with water vapour; however, the primordial atmospheres have been always assumed to have the solar abundances. Here we integrate the 1D structure of such an enriched atmosphere of sub-Earths embedded in a protoplanetary disc around an M dwarf of 0.3$\, \mathrm{M}_\odot$ and investigate the effects of water enrichment on the atmospheric properties with focus on water amount. We find that the well-mixed highly enriched atmosphere is more massive by a few orders of magnitude than the solar-abundance atmosphere, and that even a Mars-mass planet can obtain water comparable to the present Earth’s oceans. Although close-in Mars-mass planets likely lose the captured water via disc dispersal and photoevaporation, these results suggest that there are more sub-Earths with Earth-like water contents than previously predicted. How much water terrestrial planets really obtain and retain against subsequent loss, however, depends on efficiencies of water production, mixing in the atmosphere and magma ocean, and photoevaporation, detailed investigation for which should be made in the future.
4
Modirrousta-Galian, Darius, et Jun Korenaga. « The Diffusion Limit of Photoevaporation in Primordial Planetary Atmospheres ». Astrophysical Journal 965, no 1 (1 avril 2024) : 97. http://dx.doi.org/10.3847/1538-4357/ad276f.
Texte intégralRésumé :
Abstract Photoevaporation is thought to play an important role in early planetary evolution. In this study, we investigate the diffusion limit of X-ray- and ultraviolet-induced photoevaporation in primordial atmospheres. We find that compositional fractionation resulting from mass loss is more significant than currently recognized, because it is controlled by the conditions at the top of the atmosphere, where particle collisions are less frequent. Such fractionation at the top of the atmosphere develops a compositional gradient that extends downward. The mass outflow eventually reaches a steady state in which the hydrogen loss is diffusion-limited. We derive new analytic expressions for the diffusion-limited mass-loss rate and the crossover mass.
5
Sinclair, Catriona A., Mark C. Wyatt, Alessandro Morbidelli et David Nesvorný. « Evolution of the Earth’s atmosphere during Late Veneer accretion ». Monthly Notices of the Royal Astronomical Society 499, no 4 (16 octobre 2020) : 5334–62. http://dx.doi.org/10.1093/mnras/staa3210.
Texte intégralRésumé :
ABSTRACT Recent advances in our understanding of the dynamical history of the Solar system have altered the inferred bombardment history of the Earth during accretion of the Late Veneer, after the Moon-forming impact. We investigate how the bombardment by planetesimals left-over from the terrestrial planet region after terrestrial planet formation, as well as asteroids and comets, affects the evolution of Earth’s early atmosphere. We develop a new statistical code of stochastic bombardment for atmosphere evolution, combining prescriptions for atmosphere loss and volatile delivery derived from hydrodynamic simulations and theory with results from dynamical modelling of realistic populations of impactors. We find that for an initially Earth-like atmosphere, impacts cause moderate atmospheric erosion with stochastic delivery of large asteroids, giving substantial growth (× 10) in a few ${{\ \rm per\ cent}}$ of cases. The exact change in atmosphere mass is inherently stochastic and dependent on the dynamics of the left-over planetesimals. We also consider the dependence on unknowns including the impactor volatile content, finding that the atmosphere is typically completely stripped by especially dry left-over planetesimals ($\lt 0.02 ~ {{\ \rm per\ cent}}$ volatiles). Remarkably, for a wide range of initial atmosphere masses and compositions, the atmosphere converges towards similar final masses and compositions, i.e. initially low-mass atmospheres grow, whereas massive atmospheres deplete. While the final properties are sensitive to the assumed impactor properties, the resulting atmosphere mass is close to that of current Earth. The exception to this is that a large initial atmosphere cannot be eroded to the current mass unless the atmosphere was initially primordial in composition.
6
Saxena, Prabal, Lindy Elkins-Tanton, Noah Petro et Avi Mandell. « A model of the primordial lunar atmosphere ». Earth and Planetary Science Letters 474 (septembre 2017) : 198–205. http://dx.doi.org/10.1016/j.epsl.2017.06.031.
Texte intégral
7
Kurosaki, Kenji, Yasunori Hori, Masahiro Ogihara et Masanobu Kunitomo. « Evolution of a Water-rich Atmosphere Formed by a Giant Impact on an Earth-sized Planet ». Astrophysical Journal 957, no 2 (31 octobre 2023) : 67. http://dx.doi.org/10.3847/1538-4357/acfe0a.
Texte intégralRésumé :
Abstract The atmosphere of a terrestrial planet that is replenished with secondary gases should have accumulated hydrogen-rich gas from its protoplanetary disk. Although a giant impact blows off a large fraction of the primordial atmosphere of a terrestrial planet in the late formation stage, the remaining atmosphere can become water-rich via chemical reactions between hydrogen and vaporized core material. We find that a water-rich postimpact atmosphere forms when a basaltic or CI chondrite core is assumed. In contrast, little postimpact water is generated for an enstatite chondrite core. We investigate the X-ray- and UV-driven mass loss from an Earth-mass planet with an impact-induced multicomponent H2–He–H2O atmosphere for Gyr. We show that water is left in the atmosphere of an Earth-mass planet when the low flux of escaping hydrogen cannot drag water upward via collisions. For a water-dominated atmosphere to form, the atmospheric mass fraction of an Earth-mass planet with an oxidizing core after a giant impact must be less than a few times 0.1%. We also find that Earth-mass planets with water-dominated atmospheres can exist at semimajor axes ranging from a few times 0.1 au to a few au around a Sun-like star, depending on the mass-loss efficiency. Such planets are important targets for atmospheric characterization in the era of JWST. Our results indicate that efficient mixing between hydrogen and rocky components during giant impacts can play a role in the production of water in an Earth-mass planet.
8
Melosh, H. J., et A. M. Vickery. « Impact erosion of the primordial atmosphere of Mars ». Nature 338, no 6215 (avril 1989) : 487–89. http://dx.doi.org/10.1038/338487a0.
Texte intégral
9
Biersteker, John B., et Hilke E. Schlichting. « Losing oceans : The effects of composition on the thermal component of impact-driven atmospheric loss ». Monthly Notices of the Royal Astronomical Society 501, no 1 (26 novembre 2020) : 587–95. http://dx.doi.org/10.1093/mnras/staa3614.
Texte intégralRésumé :
ABSTRACT The formation of the Solar system’s terrestrial planets concluded with a period of giant impacts. Previous works examining the volatile loss caused by the impact shock in the moon-forming impact find atmospheric losses of at most 20–30 per cent and essentially no loss of oceans. However, giant impacts also result in thermal heating, which can lead to significant atmospheric escape via a Parker-type wind. Here we show that H2O and other high-mean molecular weight outgassed species can be efficiently lost through this thermal wind if present in a hydrogen-dominated atmosphere, substantially altering the final volatile inventory of terrestrial planets. We demonstrate that a giant impact during terrestrial planet formation can remove several Earth oceans’ worth of H2O, and other heavier volatile species, together with a primordial hydrogen-dominated atmosphere. These results may offer an explanation for the observed depletion in Earth’s light noble gas budget and for its depleted xenon inventory, which suggest that Earth underwent significant atmospheric loss by the end of its accretion. Because planetary embryos are massive enough to accrete primordial hydrogen envelopes and because giant impacts are stochastic and occur concurrently with other early atmospheric evolutionary processes, our results suggest a wide diversity in terrestrial planet volatile budgets.
10
Ueda, Hisahiro, et Takazo Shibuya. « Composition of the Primordial Ocean Just after Its Formation : Constraints from the Reactions between the Primitive Crust and a Strongly Acidic, CO2-Rich Fluid at Elevated Temperatures and Pressures ». Minerals 11, no 4 (6 avril 2021) : 389. http://dx.doi.org/10.3390/min11040389.
Texte intégralRésumé :
The Hadean was an enigmatic period in the Earth’s history when ocean formation and the emergence of life may have occurred. However, minimal geological evidence is left from this period. To understand the primordial ocean’s composition, we focused on the ocean’s formation processes from CO2- and HCl-bearing water vapor in the high-temperature atmosphere. When the temperature of the lower atmosphere fell below the critical point, high-temperature rain reached the ground surface. Then, hydrothermal reactions between the subcritical fluid and primordial crust started. Eventually, a liquid ocean emerged on the completely altered crust as the temperature decreased to approximately 25 °C. Here, we conducted two experiments and modeling to simulate the reactions of hypothetical primordial crustal rock (basalt or komatiite). The results indicate that the primordial ocean was mildly acidic and rich in CO2, Mg, and Ca relative to Na, irrespective of the rock type, which is different from the modern equivalents. Therefore, unlike the present seawater, the primordial seawater could have been carbonic, bitter, and harsh rather than salty.
11
Zhou, Li, Bo Ma, Yonghao Wang et Yinan Zhu. « Hubble WFC3 Spectroscopy of the Rocky Planet L 98–59 b : No Evidence for a Cloud-free Primordial Atmosphere ». Astronomical Journal 164, no 5 (19 octobre 2022) : 203. http://dx.doi.org/10.3847/1538-3881/ac8fe9.
Texte intégralRésumé :
Abstract We are using archived data from HST of transiting exoplanet L 98-59 b to place constraints on its potentially hot atmosphere. We analyze the data from five transit visits and extract the final combined transmission spectrum using Iraclis. Then we use the inverse atmospheric retrieval code TauREx to analyze the combined transmission spectrum. There is a weak absorption feature near 1.40 μm and 1.55 μm in the transmission spectrum, which can be modeled by a cloudy atmosphere with abundant hydrogen cyanide (HCN). However, the unrealistically high abundance of HCN derived cannot be explained by any equilibrium chemical model with reasonable assumptions. Thus, the likeliest scenario is that L 98-59 b has a flat, featureless transmission spectrum in the WFC3/G141 bandpass due to a thin atmosphere with high mean molecular weight, an atmosphere with an opaque aerosol layer, or no atmosphere, and it is very unlikely for L 98-59 b to have a clear hydrogen-dominated primary atmosphere. Due to the narrow wavelength coverage and low spectral resolution of HST/WFC3 G141 grism observation, we cannot tell these different scenarios apart. Our simulation shows future higher precision measurements over wider wavelengths from the James Webb Space Telescope can be used to better characterize the planetary atmosphere of L 98-59 b.
12
NAKAZAWA, Kiyoshi, Hiroshi MIZUNO, Minoru SEKIYA et Chushiro HAYASHI. « Structure of the primordial atmosphere surrounding the early-earth. » Journal of geomagnetism and geoelectricity 37, no 8 (1985) : 781–99. http://dx.doi.org/10.5636/jgg.37.781.
Texte intégral
13
Scarsdale, Nicholas, Nicholas Wogan, Hannah R. Wakeford, Nicole L. Wallack, Natasha E. Batalha, Lili Alderson, Artyom Aguichine et al. « JWST COMPASS : The 3–5 μm Transmission Spectrum of the Super-Earth L 98-59 c ». Astronomical Journal 168, no 6 (19 novembre 2024) : 276. http://dx.doi.org/10.3847/1538-3881/ad73cf.
Texte intégralRésumé :
Abstract We present a JWST Near-InfraRed Spectrograph (NIRSpec) transmission spectrum of the super-Earth exoplanet L 98-59 c. This small (R p = 1.385 ± 0.085R ⊕, M p = 2.22 ± 0.26 R ⊕), warm (T eq = 553 K) planet resides in a multiplanet system around a nearby, bright (J = 7.933) M3V star. We find that the transmission spectrum of L 98-59 c is featureless at the precision of our data. We achieve precisions of 22 ppm in NIRSpec G395H’s NRS1 detector and 36 ppm in the NRS2 detector at a resolution R ∼ 200 (30 pixel wide bins). At this level of precision, we are able rule out primordial H2–He atmospheres across a range of cloud pressure levels up to at least ∼0.1 mbar. By comparison to atmospheric forward models, we also rule out atmospheric metallicities below ∼300× solar at 3σ (or, equivalently, atmospheric mean molecular weights below ∼10 g mol−1). We also rule out pure methane atmospheres. The remaining scenarios that are compatible with our data include a planet with no atmosphere at all, or higher-mean-molecular-weight atmospheres, such as CO2- or H2O-rich atmospheres. This study adds to a growing body of evidence suggesting that planets ≲1.5 R ⊕ lack extended atmospheres.
14
Mukhopadhyay, Sujoy, et Rita Parai. « Noble Gases : A Record of Earth's Evolution and Mantle Dynamics ». Annual Review of Earth and Planetary Sciences 47, no 1 (30 mai 2019) : 389–419. http://dx.doi.org/10.1146/annurev-earth-053018-060238.
Texte intégralRésumé :
Noble gases have played a key role in our understanding of the origin of Earth's volatiles, mantle structure, and long-term degassing of the mantle. Here we synthesize new insights into these topics gained from high-precision noble gas data. Our analysis reveals new constraints on the origin of the terrestrial atmosphere, the presence of nebular neon but chondritic krypton and xenon in the mantle, and a memory of multiple giant impacts during accretion. Furthermore, the reservoir supplying primordial noble gases to plumes appears to be distinct from the mid-ocean ridge basalt (MORB) reservoir since at least 4.45 Ga. While differences between the MORB mantle and plume mantle cannot be explained solely by recycling of atmospheric volatiles, injection and incorporation of atmospheric-derived noble gases into both mantle reservoirs occurred over Earth history. In the MORB mantle, the atmospheric-derived noble gases are observed to be heterogeneously distributed, reflecting inefficient mixing even within the vigorously convecting MORB mantle. ▪ Primordial noble gases in the atmosphere were largely derived from planetesimals delivered after the Moon-forming giant impact. ▪ Heterogeneities dating back to Earth's accretion are preserved in the present-day mantle. ▪ Mid-ocean ridge basalts and plume xenon isotopic ratios cannot be related by differential degassing or differential incorporation of recycled atmospheric volatiles. ▪ Differences in mid-ocean ridge basalts and plume radiogenic helium, neon, and argon ratios can be explained through the lens of differential long-term degassing.
15
Misener, William, et Hilke E. Schlichting. « To cool is to keep : residual H/He atmospheres of super-Earths and sub-Neptunes ». Monthly Notices of the Royal Astronomical Society 503, no 4 (27 mars 2021) : 5658–74. http://dx.doi.org/10.1093/mnras/stab895.
Texte intégralRésumé :
ABSTRACT Super-Earths and sub-Neptunes are commonly thought to have accreted hydrogen/helium envelopes, consisting of a few to ten percent of their total mass, from the primordial gas disc. Subsequently, hydrodynamic escape driven by core-powered mass-loss and/or photoevaporation likely stripped much of these primordial envelopes from the lower mass and closer-in planets to form the super-Earth population. In this work, we show that after undergoing core-powered mass-loss, some super-Earths can retain small residual H/He envelopes. This retention is possible because, for significantly depleted atmospheres, the density at the radiative–convective boundary drops sufficiently such that the cooling time-scale becomes shorter than the mass-loss time-scale. The residual envelope is therefore able to contract, terminating further mass-loss. Using analytic calculations and numerical simulations, we show that the mass of primordial H/He envelope retained as a fraction of the planet’s total mass, fret, increases with increasing planet mass, Mc, and decreases with increasing equilibrium temperature, Teq, scaling as $f_\mathrm{ret} \propto M_\mathrm{c}^{3/2} T_\mathrm{eq}^{-1/2} \exp {[M_\mathrm{c}^{3/4} T_\mathrm{eq}^{-1}]}$. fret varies from <10−8 to about 10−3 for typical super-Earth parameters. To first order, the exact amount of left-over H/He depends on the initial envelope mass, the planet mass, its equilibrium temperature, and the envelope’s opacity. These residual hydrogen envelopes reduce the atmosphere’s mean molecular weight compared to a purely secondary atmosphere, a signature observable by current and future facilities. These remnant atmospheres may, however, in many cases be vulnerable to long-term erosion by photoevaporation. Any residual hydrogen envelope likely plays an important role in the long-term physical evolution of super-Earths, including their geology and geochemistry.
16
Micca Longo, Gaia, Luca Vialetto, Paola Diomede, Savino Longo et Vincenzo Laporta. « Plasma Modeling and Prebiotic Chemistry : A Review of the State-of-the-Art and Perspectives ». Molecules 26, no 12 (16 juin 2021) : 3663. http://dx.doi.org/10.3390/molecules26123663.
Texte intégralRésumé :
We review the recent progress in the modeling of plasmas or ionized gases, with compositions compatible with that of primordial atmospheres. The plasma kinetics involves elementary processes by which free electrons ultimately activate weakly reactive molecules, such as carbon dioxide or methane, thereby potentially starting prebiotic reaction chains. These processes include electron–molecule reactions and energy exchanges between molecules. They are basic processes, for example, in the famous Miller-Urey experiment, and become relevant in any prebiotic scenario where the primordial atmosphere is significantly ionized by electrical activity, photoionization or meteor phenomena. The kinetics of plasma displays remarkable complexity due to the non-equilibrium features of the energy distributions involved. In particular, we argue that two concepts developed by the plasma modeling community, the electron velocity distribution function and the vibrational distribution function, may unlock much new information and provide insight into prebiotic processes initiated by electron–molecule collisions.
17
Trafton, L., S. A. Stern et G. R. Gladstone. « The Pluto-Charon system : The escape of charon's primordial atmosphere ». Icarus 74, no 1 (avril 1988) : 108–20. http://dx.doi.org/10.1016/0019-1035(88)90033-4.
Texte intégral
18
Kubyshkina, Daria, et Aline A. Vidotto. « How does the mass and activity history of the host star affect the population of low-mass planets ? » Monthly Notices of the Royal Astronomical Society 504, no 2 (27 mars 2021) : 2034–50. http://dx.doi.org/10.1093/mnras/stab897.
Texte intégralRésumé :
ABSTRACT The evolution of the atmospheres of low- and intermediate-mass planets is strongly connected to the physical properties of their host stars. The types and the past activities of planet-hosting stars can, therefore, affect the overall planetary population. In this paper, we perform a comparative study of sub-Neptune-like planets orbiting stars of different masses and different evolutionary histories. We discuss the general patterns of the evolved population as a function of parameters and environments of planets. As a model of the atmospheric evolution, we employ the own framework combining planetary evolution in Modules for Experiments in Stellar Astrophysics (mesa) with the realistic prescription of the escape of hydrogen-dominated atmospheres. We find that the final populations look qualitatively similar in terms of the atmospheres survival around different stars, but qualitatively different, with this difference accentuated for planets orbiting more massive stars. We show that a planet has larger chances of keeping its primordial atmosphere in the habitable zone of a solar-mass star compared to M or K dwarfs and if it starts the evolution having a relatively compact envelope. We also address the problem of the uncertain initial temperatures (luminosities) of planets and show that this issue is only of particular importance for planets exposed to extreme atmospheric mass losses.
19
Atri, Dimitra, et Shane R. Carberry Mogan. « Stellar flares versus luminosity : XUV-induced atmospheric escape and planetary habitability ». Monthly Notices of the Royal Astronomical Society : Letters 500, no 1 (9 novembre 2020) : L1—L5. http://dx.doi.org/10.1093/mnrasl/slaa166.
Texte intégralRésumé :
ABSTRACT Space weather plays an important role in the evolution of planetary atmospheres. Observations have shown that stellar flares emit energy in a wide energy range (1030–1038 erg), a fraction of which lies in X-rays and extreme ultraviolet (XUV). These flares heat the upper atmosphere of a planet, leading to increased escape rates, and can result in atmospheric erosion over a period of time. Observations also suggest that primordial terrestrial planets can accrete voluminous H/He envelopes. Stellar radiation can erode these protoatmospheres over time, and the extent of this erosion has implications for the planet’s habitability. We use the energy-limited equation to calculate hydrodynamic escape rates from these protoatmospheres irradiated by XUV stellar flares and luminosity. We use the flare frequency distribution of 492 FGKM stars observed with TESS to estimate atmospheric loss in habitable zone planets. We find that for most stars, luminosity-induced escape is the main loss mechanism, with a minor contribution from flares. However, flares dominate the loss mechanism of ∼20 per cent M4–M10 stars. M0–M4 stars are most likely to completely erode both their proto- and secondary atmospheres, and M4–M10 are least likely to erode secondary atmospheres. We discuss the implications of these results on planetary habitability.
20
Libby-Roberts, Jessica E., Zachory K. Berta-Thompson, Hannah Diamond-Lowe, Michael A. Gully-Santiago, Jonathan M. Irwin, Eliza M. R. Kempton, Benjamin V. Rackham et al. « The Featureless HST/WFC3 Transmission Spectrum of the Rocky Exoplanet GJ 1132b : No Evidence for a Cloud-free Primordial Atmosphere and Constraints on Starspot Contamination ». Astronomical Journal 164, no 2 (19 juillet 2022) : 59. http://dx.doi.org/10.3847/1538-3881/ac75de.
Texte intégralRésumé :
Abstract Orbiting an M dwarf 12 pc away, the transiting exoplanet GJ 1132b is a prime target for transmission spectroscopy. With a mass of 1.7 M ⊕ and radius of 1.1 R ⊕, GJ 1132b’s bulk density indicates that this planet is rocky. Yet with an equilibrium temperature of 580 K, GJ 1132b may still retain some semblance of an atmosphere. Understanding whether this atmosphere exists and its composition will be vital for understanding how the atmospheres of terrestrial planets orbiting M dwarfs evolve. We observe five transits of GJ 1132b with the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST). We find a featureless transmission spectrum from 1.1 to 1.7 μm, ruling out cloud-free atmospheres with metallicities <300× solar with >4.8σ confidence. We combine our WFC3 results with transit depths from TESS and archival broadband and spectroscopic observations to find a featureless spectrum across 0.7 to 4.5 μm. GJ 1132b therefore has a high mean molecular weight atmosphere, possesses a high-altitude aerosol layer, or has effectively no atmosphere. Higher-precision observations are required in order to differentiate between these possibilities. We explore the impact of hot and cold starspots on the observed transmission spectrum GJ 1132b, quantifying the amplitude of spot-induced transit depth features. Using a simple Poisson model, we estimate spot temperature contrasts, spot covering fractions, and spot sizes for GJ 1132. These limits, as well as the modeling framework, may be useful for future observations of GJ 1132b or other planets transiting similarly inactive M dwarfs.
21
Cannon, Kevin M., Stephen W. Parman et John F. Mustard. « Primordial clays on Mars formed beneath a steam or supercritical atmosphere ». Nature 552, no 7683 (décembre 2017) : 88–91. http://dx.doi.org/10.1038/nature24657.
Texte intégral
22
Haq, Ehsan ul, Farwah Waseem et Abdul Baqi. « Appraisal of Temporal Variations in Atmospheric Compositions over South Asia by Addition of Various Pollutant’s in Recent Decade ». Vol 3 Issue 1 3, no 1 (8 février 2021) : 1–15. http://dx.doi.org/10.33411/ijist/2021030101.
Texte intégralRésumé :
Atmosphere is an envelope of gasses and aerosols around the planet, 99% of the total mass of atmospheric gases resides within 32km from Earth’s surface in vertical column. From primordial era to current scenario composition of earth endured numerous drastic modifications. In last decade atmosphere had undergone a vigorous change by the addition of many pollutants in both natural and anthropogenic aspects. South Asia is a densely populated; masses here are in a transition state, this developing nation in this region considerably done enough damage to the atmosphere of south Asia by inserting multiple pollutants in atmosphere in a number of anthropogenic activities. These pollutants piled up as a serious danger for people around the globe like Methane (CH4), Sulphur Dioxide (SO2), Carbon Monoxide (CO) Nitrogen Dioxide (NO2), Carbon Dioxide (CO2), Formaldehydes (HCHO) and tropospheric Ozone (O3) etc. “Environmental Remote Sensing” has arisen as a great tool of modern era to get fruitful and precise results to monitor these variations in atmospheric pollutants. The NASA’s (National Aeronautics and Space Administration), Geospatial Interactive Online Visualization ANd aNalysis Infrastructure (Giovanni) system provides access to a wide variety of NASA’s remote sensing data, Variety of environmental data types has permitted the use of Giovanni for different applications to define addition and increase in concentration of various pollutants. Spatio temporal variation of pollutants shows their concentration increased in last decade and in last three years the concentration boosted as compared to last seven years.
23
Yalinewich, Almog, et Matthew E. Caplan. « Crater morphology of primordial black hole impacts ». Monthly Notices of the Royal Astronomical Society : Letters 505, no 1 (10 juin 2021) : L115—L119. http://dx.doi.org/10.1093/mnrasl/slab063.
Texte intégralRésumé :
ABSTRACT In this work, we propose a novel campaign for constraining relativistically compact massive compact halo object (MACHO) dark matter, such as primordial black holes (PBHs), using the Moon as a detector. PBHs of about 1019 to 1022 g may be sufficiently abundant to have collided with the Moon in the history of the Solar system. We show that the crater profiles of a PBH collision differ from traditional impactors and may be detectable in high-resolution lunar surface scans now available. Any candidates may serve as sites for in situ measurements to identify high-pressure phases of matter which may have formed near the PBH during the encounter. While we primarily consider PBH dark matter, the discussion generalizes to the entire family of MACHO candidates with relativistic compactness. Moreover, we focus on the Moon since it has been studied well, but the same principles can be applied to other rocky bodies in our Solar system without an atmosphere.
24
Mizuno, Hiroshi, et Kiyoshi Nakazawa. « Chapter 22. Primordial Atmosphere Surrounding a Protoplanet and Formation of Jovian Planets ». Progress of Theoretical Physics Supplement 96 (1988) : 266–73. http://dx.doi.org/10.1143/ptps.96.266.
Texte intégral
25
Modirrousta-Galian, D., B. Stelzer, E. Magaudda, J. Maldonado, M. Güdel, J. Sanz-Forcada, B. Edwards et G. Micela. « GJ 357 b ». Astronomy & ; Astrophysics 641 (septembre 2020) : A113. http://dx.doi.org/10.1051/0004-6361/202038280.
Texte intégralRésumé :
Aims. In this paper we present a deep X-ray observation of the nearby M dwarf GJ 357 and use it to put constraints on the atmospheric evolution of its planet, GJ 357 b. We also analyse the systematic errors in the stellar parameters of GJ 357 in order to see how they affect the perceived planetary properties. Methods. By comparing the observed X-ray luminosity of its host star, we estimate the age of GJ 357 b as derived from a recent XMM-Newton observation (log Lx [erg s−1] = 25.73), with Lx− age relations for M dwarfs. We find that GJ 357 presents one of the lowest X-ray activity levels ever measured for an M dwarf, and we put a lower limit on its age of 5 Gyr. Using this age limit, we performed a backwards reconstruction of the original primordial atmospheric reservoir. Furthermore, by considering the systematic errors in the stellar parameters, we find a range of possible planetary masses, radii, and densities. Results. From the backwards reconstruction of the irradiation history of GJ 357 b’s we find that the upper limit of its initial primordial atmospheric mass is ~38 M⊕. An initial atmospheric reservoir significantly larger than this may have survived through the X-ray and ultraviolet irradiation history, which would not be consistent with current observations that suggest a telluric composition. However, given the relatively small mass of GJ 357 b, even accreting a primordial envelope ≳10 M⊕ would have been improbable as an unusually low protoplanetary disc opacity, large-scale migration, and a weak interior luminosity would have been required. For this reason, we discard the possibility that GJ 357 b was born as a Neptunian- or Jovian-sized body. In spite of the unlikelihood of a currently existing primordial envelope, volcanism and outgassing may have contributed to a secondary atmosphere. Under this assumption, we present three different synthetic IR spectra for GJ 357 b that one might expect, consisting of 100% CO2, 100% SO2, and 75% N2, 24% CO2 and 1% H2O, respectively. Future observations with space-based IR spectroscopy missions will be able to test these models. Finally, we show that the uncertainties in the stellar and planetary quantities do not have a significant effect on the estimated mass or radius of GJ 357 b.
26
Micca Longo, Gaia, et Savino Longo. « The role of primordial atmosphere composition in organic matter delivery to early Earth ». Rendiconti Lincei. Scienze Fisiche e Naturali 31, no 1 (10 février 2020) : 53–64. http://dx.doi.org/10.1007/s12210-020-00878-x.
Texte intégral
27
Molaverdikhani, K., Ch Helling, B. W. P. Lew, R. J. MacDonald, D. Samra, N. Iro, P. Woitke et V. Parmentier. « Understanding the atmospheric properties and chemical composition of the ultra-hot Jupiter HAT-P-7b ». Astronomy & ; Astrophysics 635 (mars 2020) : A31. http://dx.doi.org/10.1051/0004-6361/201937044.
Texte intégralRésumé :
Aims. The atmospheres of ultra-hot Jupiters (UHJs) are commonly considered to be at thermochemical equilibrium. We aim to provide disequilibrium chemistry maps for a global understanding of the chemistry in the atmosphere of HAT-P-7b and assess the importance of disequilibrium chemistry on UHJs. Methods. We applied a hierarchical modeling approach using 97 1D atmospheric profiles from a 3D general circulation model of HAT-P-7b. For each atmospheric 1D profile, we evaluated our kinetic cloud formation model consistently with the local gas-phase composition in chemical equilibrium. This served as input to study the quenching of dominating CHNO-binding molecules. We evaluated quenching results from a zeroth-order approximation in comparison to a kinetic gas-phase approach. Results. We find that the zeroth-order approach of estimating quenching points agrees well with the full gas-kinetic modeling results. However, it underestimates the quenching levels by about one order of magnitude at high temperatures. Chemical disequilibrium has the greatest effect on the nightside and morning abundance of species such as H, H2O, CH4, CO2, HCN, and all CnHm molecules; heavier CnHm molecules are more affected by disequilibrium processes. The CO abundance, however, is affected only marginally. While dayside abundances also notably change, those around the evening terminator of HAT-P-7b are the least affected by disequilibrium processes. The latter finding may partially explain the consistency of observed transmission spectra of UHJs with atmospheres in thermochemical equilibrium. Photochemistry only negligibly affects molecular abundances and quenching levels. Conclusions. In general, the quenching points of the atmosphere of HAT-P-7b are at much lower pressures than in the cooler hot-jupiters. We propose several avenues to determining the effect of disequilibrium processes on UHJs that are in general based on abundance and opacity measurements at different local times. It remains a challenge to completely disentangle this from the chemical effects of clouds and that of a primordial nonsolar abundance.
28
Schroeder I, Isaac R. H. G., Kathrin Altwegg, Hans Balsiger, Jean-Jacques Berthelier, Johan De Keyser, Björn Fiethe, Stephen A. Fuselier et al. « 16O/18O ratio in water in the coma of comet 67P/Churyumov-Gerasimenko measured with the Rosetta/ROSINA double-focusing mass spectrometer ». Astronomy & ; Astrophysics 630 (20 septembre 2019) : A29. http://dx.doi.org/10.1051/0004-6361/201833806.
Texte intégralRésumé :
The European Space Agency spacecraft Rosetta accompanied the Jupiter-family comet 67P/Churyumov-Gerasimenko for over 2 yr along its trajectory through the inner solar system. Between 2014 and 2016, it performed almost continuous in situ measurements of the comet’s gaseous atmosphere in close proximity to its nucleus. In this study, the 16O/18O ratio of H2O in the coma of 67P/Churyumov-Gerasimenko, as measured by the ROSINA DFMS mass spectrometer onboard Rosetta, was determined from the ratio of H216O/H218O and 16OH/18OH. The value of 445 ± 35 represents an ~11% enrichment of 18O compared with the terrestrial ratio of 498.7 ± 0.1. This cometary value is consistent with the comet containing primordial water, in accordance with leading self-shielding models. These models predict primordial water to be between 5 and 20% enriched in heavier oxygen isotopes compared to terrestrial water.
29
Jaupart, Etienne, Sebatien Charnoz et Manuel Moreira. « Primordial atmosphere incorporation in planetary embryos and the origin of Neon in terrestrial planets ». Icarus 293 (septembre 2017) : 199–205. http://dx.doi.org/10.1016/j.icarus.2017.04.022.
Texte intégral
30
Afshordi, N., R. B. Mann et R. Pourhasan. « A holographic big bang ? » International Journal of Modern Physics D 24, no 12 (octobre 2015) : 1544029. http://dx.doi.org/10.1142/s0218271815440290.
Texte intégralRésumé :
We present a cosmological model in which the Universe emerges out of the collapse of a five-dimensional (5D) star as a spherical three-brane. The initial singularity of the big bang becomes hidden behind a causal horizon. Near scale-invariant primordial curvature perturbations can be induced on the brane via a thermal atmosphere that is in equilibrium with the brane, circumventing the need for a separate inflationary process and providing an important test of the model.
31
Ferus, Martin, Fabio Pietrucci, Antonino Marco Saitta, Antonín Knížek, Petr Kubelík, Ondřej Ivanek, Violetta Shestivska et Svatopluk Civiš. « Formation of nucleobases in a Miller–Urey reducing atmosphere ». Proceedings of the National Academy of Sciences 114, no 17 (10 avril 2017) : 4306–11. http://dx.doi.org/10.1073/pnas.1700010114.
Texte intégralRésumé :
The Miller–Urey experiments pioneered modern research on the molecular origins of life, but their actual relevance in this field was later questioned because the gas mixture used in their research is considered too reducing with respect to the most accepted hypotheses for the conditions on primordial Earth. In particular, the production of only amino acids has been taken as evidence of the limited relevance of the results. Here, we report an experimental work, combined with state-of-the-art computational methods, in which both electric discharge and laser-driven plasma impact simulations were carried out in a reducing atmosphere containing NH3 + CO. We show that RNA nucleobases are synthesized in these experiments, strongly supporting the possibility of the emergence of biologically relevant molecules in a reducing atmosphere. The reconstructed synthetic pathways indicate that small radicals and formamide play a crucial role, in agreement with a number of recent experimental and theoretical results.
32
Montoya, David. « Hostilidad perpetua, transformaciones transitorias : Persona, cuerpo y moralidad entre los tsotsiles de Chamula, Chiapas / Perpetual hostility, transitory transformations : Person, body and morality between the tsotsiles of Chamula, Chiapas ». Revista Trace, no 78 (31 juillet 2020) : 67. http://dx.doi.org/10.22134/trace.78.2020.735.
Texte intégralRésumé :
El actual estudio etnográfico da cuenta de que lo chon –un aspecto de la persona, generalmente, asociado a lo animal– está relacionado con un estado de permanente hostilidad, presente en el mundo desde tiempos primordiales. Este aspecto, a la vez que potencia la vulnerabilidad entre los humanos, resalta la fortaleza de otros seres, como Dios y el Pukuj. En la búsqueda de lidiar con esa atmósfera de hostilidad y, de mitigar su propia vulnerabilidad, la humanidad experimenta múltiples transformaciones morales-corporales.Abstract: This ethnographic study shows that the chon –an aspect of the person, generally associated with the animal– is related to an state of permanent hostility, given in the world since primordial times. Although this aspect, while enhancing vulnerability among humans, highlights the strength of other beings such as God and the Pukuj. Therefore, to deal with this atmosphere of hostility and, therefore, to mitigate its own vulnerability, humanity undergoes multiple transformations moral-bodily. Keywords: chon; tsotsiles; humanity; vulnerability; morale.Résumé : Cette étude ethnographique montre que le chon –un aspect de la personne, généralment associé à l’animal– est lié à l’état d’hostilité qui caractérise le monde. Cet aspect, tout en renforçant la vulnérabilité des humains, met en évidence la force d’autres êtres tels que Dieu et les Pukuj. Dans sa quête pour faire face à cette atmosphère d’hostilité et, par conséquent, pour atténuer sa propre vulnérabilité, l’humanité subit de multiples transformations morales-corporelles.Mots-clés: chon ; tsotsiles ; vulnérabilité ; humanité ; moral.
33
Swindle, T. D., et J. H. Jones. « The xenon isotopic composition of the primordial Martian atmosphere : Contributions from solar and fission components ». Journal of Geophysical Research : Planets 102, E1 (1 janvier 1997) : 1671–78. http://dx.doi.org/10.1029/96je03110.
Texte intégral
34
Anderson, Don L. « A model to explain the various paradoxes associated with mantle noble gas geochemistry ». Proceedings of the National Academy of Sciences 95, no 16 (4 août 1998) : 9087–92. http://dx.doi.org/10.1073/pnas.95.16.9087.
Texte intégralRésumé :
As a result of an energetic accretion, the Earth is a volatile-poor and strongly differentiated planet. The volatile elements can be accounted for by a late veneer (≈1% of total mass of the Earth). The incompatible elements are strongly concentrated into the exosphere (atmosphere, oceans, sediments, and crust) and upper mantle. Recent geochemical models invoke a large primordial undegassed reservoir with chondritic abundances of uranium and helium, which is clearly at odds with mass and energy balance calculations. The basic assumption behind these models is that excess “primordial” 3He is responsible for 3He/4He ratios higher than the average for midocean ridge basalts. The evidence however favors depletion of 3He and excessive depletion of 4He and, therefore, favors a refractory, residual (low U, Th) source Petrological processes such as melt-crystal and melt-gas separation fractionate helium from U and Th and, with time, generate inhomogeneities in the 3He/4He ratio. A self-consistent model for noble gases involves a gas-poor planet with trapping of CO2 and noble gases in the shallow mantle. Such trapped gases are released by later tectonic and magmatic processes. Most of the mantle was depleted and degassed during the accretion process. High 3He/4He gases are viewed as products of ancient gas exsolution stored in low U environments, rather than products of primordial reservoirs.
35
Chakrabarty, Aritra, et Gijs D. Mulders. « Where Are the Water Worlds ? Identifying Exo-water-worlds Using Models of Planet Formation and Atmospheric Evolution ». Astrophysical Journal 966, no 2 (1 mai 2024) : 185. http://dx.doi.org/10.3847/1538-4357/ad3802.
Texte intégralRésumé :
Abstract Planet formation models suggest that the small exoplanets that migrate from beyond the snowline of the protoplanetary disk likely contain water-ice-rich cores (∼50% by mass), also known as water worlds. While the observed radius valley of the Kepler planets is well explained by the atmospheric dichotomy of the rocky planets, precise measurements of the mass and radius of the transiting planets hint at the existence of these water worlds. However, observations cannot confirm the core compositions of those planets, owing to the degeneracy between the density of a bare water-ice-rich planet and the bulk density of a rocky planet with a thin atmosphere. We combine different formation models from the Genesis library with atmospheric escape models, such as photoevaporation and impact stripping, to simulate planetary systems consistent with the observed radius valley. We then explore the possibility of water worlds being present in the currently observed sample by comparing them with simulated planets in the mass–radius–orbital period space. We find that the migration models suggest ≳10% and ≳20% of the bare planets, i.e., planets without primordial H/He atmospheres, to be water-ice-rich around G- and M-type host stars, respectively, consistent with the mass–radius distributions of the observed planets. However, most of the water worlds are predicted to be outside a period of 10 days. A unique identification of water worlds through radial velocity and transmission spectroscopy is likely to be more successful when targeting such planets with longer orbital periods.
36
Atreya, Sushil K., Melissa G. Trainer, Heather B. Franz, Michael H. Wong, Heidi L. K. Manning, Charles A. Malespin, Paul R. Mahaffy et al. « Primordial argon isotope fractionation in the atmosphere of Mars measured by the SAM instrument on Curiosity and implications for atmospheric loss ». Geophysical Research Letters 40, no 21 (6 novembre 2013) : 5605–9. http://dx.doi.org/10.1002/2013gl057763.
Texte intégral
37
Xing, Lei, Dongdong Yan et Jianheng Guo. « The Mass Fractionation of Helium in the Escaping Atmosphere of HD 209458b* ». Astrophysical Journal 953, no 2 (1 août 2023) : 166. http://dx.doi.org/10.3847/1538-4357/ace43f.
Texte intégralRésumé :
Abstract The absorption signals of metastable He in HD 209458b and several other exoplanets can be explained via an escaping atmosphere model with a subsolar He/H ratio. The low abundance of helium can be a result of planet formation if there is a small amount of helium in their primordial atmosphere. However, another possibility is that the low He/H ratio is caused by the process of mass fractionation of helium in the atmosphere. In order to investigate the effect of fractionation in the hydrogen-helium atmosphere, we developed a self-consistent multi-fluid 1D hydrodynamic model based on the well-known open-source MHD code PLUTO. Our simulations show that a lower He/H ratio can be produced spontaneously in the multi-fluid model. We further modeled the transmission spectra of He 10830 lines for HD 209458b in a broad parameter space. The transmission spectrum of the observation can be fitted in the condition of 1.80 times the X-ray and extreme-ultraviolet flux of the quiet Sun. Meanwhile, the ratio of the escaping flux of helium to hydrogen, F He/F H, is 0.039. Our results indicate that the mass fractionation of helium to hydrogen can naturally interpret the low He/H ratio required by the observation. Thus, in the escaping atmosphere of HD 209458b, decreasing the abundance of helium in the atmosphere is not needed even if its He abundance is similar to that of the Sun. The simulation presented in this work hints that in the escaping atmosphere, mass fractionation can also occur on other exoplanets, which needs to be explored further.
38
Sasaki, Sho, et Kiyoshi Nakazawa. « Origin of isotopic fractionation of terrestrial Xe : hydrodynamic fractionation during escape of the primordial H2He atmosphere ». Earth and Planetary Science Letters 89, no 3-4 (août 1988) : 323–34. http://dx.doi.org/10.1016/0012-821x(88)90120-3.
Texte intégral
39
Ávila, Patricio Javier, Tommaso Grassi, Stefano Bovino, Andrea Chiavassa, Barbara Ercolano, Sebastian Oscar Danielache et Eugenio Simoncini. « Presence of water on exomoons orbiting free-floating planets : a case study ». International Journal of Astrobiology 20, no 4 (8 juin 2021) : 300–311. http://dx.doi.org/10.1017/s1473550421000173.
Texte intégralRésumé :
AbstractA free-floating planet (FFP) is a planetary-mass object that orbits around a non-stellar massive object (e.g. a brown dwarf) or around the Galactic Centre. The presence of exomoons orbiting FFPs has been theoretically predicted by several models. Under specific conditions, these moons are able to retain an atmosphere capable of ensuring the long-term thermal stability of liquid water on their surface. We model this environment with a one-dimensional radiative-convective code coupled to a gas-phase chemical network including cosmic rays and ion-neutral reactions. We find that, under specific conditions and assuming stable orbital parameters over time, liquid water can be formed on the surface of the exomoon. The final amount of water for an Earth-mass exomoon is smaller than the amount of water in Earth oceans, but enough to host the potential development of primordial life. The chemical equilibrium time-scale is controlled by cosmic rays, the main ionization driver in our model of the exomoon atmosphere.
40
Gibson, Carl H. « Turbulence in the Ocean, Atmosphere, Galaxy, and Universe ». Applied Mechanics Reviews 49, no 5 (1 mai 1996) : 299–315. http://dx.doi.org/10.1115/1.3101929.
Texte intégralRésumé :
Flows in natural bodies of fluid often become turbulent, with eddy-like motions dominated by inertial-vortex forces. Buoyancy, Coriolis, viscous, self-gravitational, electromagnetic, and other force constraints produce a complex phase space of wave-like hydrodynamic states that interact with turbulence eddies, masquerade as turbulence, and preserve information about previous hydrodynamic states as fossil turbulence. Evidence from the ocean, atmosphere, galaxy and universe are compared with universal similarity hypotheses of Kolmogorov (1941, 1962) for turbulence velocity u, and extensions to scalar fields θ like temperature mixed by turbulence. Universal u and θ spectra of natural flows can be inferred from laboratory and computer simulations with satisfactory accuracy, but higher order spectra and the intermittency constant u of the third Kolmogorov hypothesis (1962) require measurements at the much larger Reynolds numbers found only in nature. Information about previous hydrodynamic states is preserved by Schwarz viscous and turbulence lengths and masses of self-gravitating condensates (rarely by the classical Jeans length and mass), as it is by Ozmidov, Hopfinger and Fernando scales in hydrophysical fields of the ocean and atmosphere. Viscous-gravitational formation occurred 104-105 y after the Big Bang for supercluster, cluster, and then galaxy masses of the plasma, producing the first turbulence. Condensation after plasma neutralization of the H-4He gas was to a primordial fog of sub-solar particles that persists today in galactic halos as dark matter. These gradually formed all stars, star clusters, etc (humans!) within.
41
Kubyshkina, D., L. Fossati, A. J. Mustill, P. E. Cubillos, M. B. Davies, N. V. Erkaev, C. P. Johnstone et al. « The Kepler-11 system : evolution of the stellar high-energy emission and initial planetary atmospheric mass fractions ». Astronomy & ; Astrophysics 632 (29 novembre 2019) : A65. http://dx.doi.org/10.1051/0004-6361/201936581.
Texte intégralRésumé :
The atmospheres of close-in planets are strongly influenced by mass loss driven by the high-energy (X-ray and extreme ultraviolet, EUV) irradiation of the host star, particularly during the early stages of evolution. We recently developed a framework to exploit this connection and enable us to recover the past evolution of the stellar high-energy emission from the present-day properties of its planets, if the latter retain some remnants of their primordial hydrogen-dominated atmospheres. Furthermore, the framework can also provide constraints on planetary initial atmospheric mass fractions. The constraints on the output parameters improve when more planets can be simultaneously analysed. This makes the Kepler-11 system, which hosts six planets with bulk densities between 0.66 and 2.45 g cm−3, an ideal target. Our results indicate that the star has likely evolved as a slow rotator (slower than 85% of the stars with similar masses), corresponding to a high-energy emission at 150 Myr of between 1 and 10 times that of the current Sun. We also constrain the initial atmospheric mass fractions for the planets, obtaining a lower limit of 4.1% for planet c, a range of 3.7–5.3% for planet d, a range of 11.1–14% for planet e, a range of 1–15.6% for planet f, and a range of 4.7–8.7% for planet g assuming a disc dispersal time of 1 Myr. For planet b, the range remains poorly constrained. Our framework also suggests slightly higher masses for planets b, c, and f than have been suggested based on transit timing variation measurements. We coupled our results with published planet atmosphere accretion models to obtain a temperature (at 0.25 AU, the location of planet f) and dispersal time of the protoplanetary disc of 550 K and 1 Myr, although these results may be affected by inconsistencies in the adopted system parameters. This work shows that our framework is capable of constraining important properties of planet formation models.
42
Orell-Miquel, J., F. Murgas, E. Pallé, M. Lampón, M. López-Puertas, J. Sanz-Forcada, E. Nagel et al. « A tentative detection of He I in the atmosphere of GJ 1214 b ». Astronomy & ; Astrophysics 659 (mars 2022) : A55. http://dx.doi.org/10.1051/0004-6361/202142455.
Texte intégralRésumé :
The He I λ10833 Å triplet is a powerful tool for characterising the upper atmosphere of exoplanets and tracing possible mass loss. Here, we analysed one transit of GJ 1214 b observed with the CARMENES high-resolution spectrograph to study its atmosphere via transmission spectroscopy around the He I triplet. Although previous studies using lower resolution instruments have reported non-detections of He I in the atmosphere of GJ 1214 b, we report here the first potential detection. We reconcile the conflicting results arguing that previous transit observations did not present good opportunities for the detection of He I, due to telluric H2O absorption and OH emission contamination. We simulated those earlier observations, and show evidence that the planetary signal was contaminated. From our single non-telluric-contaminated transit, we determined an excess absorption of 2.10−0.50+0.45% (4.6 σ) with a full width at half maximum (FWHM) of 1.30−0.25+0.30 Å. The detection of He I is statistically significant at the 4.6 σ level, but repeatability of the detection could not be confirmed due to the availability of only one transit. By applying a hydrodynamical model and assuming an H/He composition of 98/2, we found that GJ 1214 b would undergo hydrodynamic escape in the photon-limited regime, losing its primary atmosphere with a mass-loss rate of (1.5–18) × 1010 g s−1 and an outflow temperature in the range of 2900–4400 K. Further high-resolution follow-up observations of GJ 1214 b are needed to confirm and fully characterise the detection of an extended atmosphere surrounding GJ 1214 b. If confirmed, this would be strong evidence that this planet has a primordial atmosphere accreted from the original planetary nebula. Despite previous intensive observations from space- and ground-based observatories, our He I excess absorption is the first tentative detection of a chemical species in the atmosphere of this benchmark sub-Neptune planet.
43
Rivera Quintero, Rosario, et Verónica Useche Ospinal. « Creating an atmosphere of enthusiasm and motivation in the classroom ». Revista Sapientía 10, no 20 (16 juillet 2021) : 34–40. http://dx.doi.org/10.54278/sapientia.v10i20.56.
Texte intégralRésumé :
En el ámbito educativo actual, la figura del docente está siendo cada vez más desestimada por parte de los mismos estudiantes, lo cual ha ido generando una serie de factores que hacen que ellos ya no se sientan motivados por aprender o encuentren diversas excusas para no querer apropiarse de sus conocimientos. A través de éste artículo, se pretende concientizar, animar y ayudar al maestro a apropiarse de su rol y ejercerlo de tal forma que pueda ser un canal que estimule el aprendizaje en sus estudiantes sin que ellos se sientan presionados ni obligados. Los tres componentes mencionados en el artículo y que ayudarán a abordar este tema son: creatividad, innovación y estimulación intelectual. Si bien en el proceso de formación, éstos deben ser desarrollados de forma conectada, muchos los ven como factores aislados entre sí o no interconectados. La correlación que estos tres elementos poseen es primordial en el manejo y organización al interior de las aulas, ya que tiene como fin interesar a los aprendices a ser más conscientes y a involucrarse más en su propio aprendizaje, sintiéndose responsables de cumplir las metas u objetivos propuestos y estimulando sus capacidades en el logro de los mismos. Por otro lado, reconocer la importancia del rol del docente, su pasión por enseñar y formar, son puntos claves para la creación de ambientes motivacionales y entusiastas, ya que esto conlleva a que los estudiantes asimilen y se interesen por aprender de manera más natural y fresca sin dejar de lado la exigencia y excelencia en cada uno de los procesos.
44
NASELSKY, P., I. NOVIKOV, YU PARIJSKIJ et P. TCIBULEV. « CMB ANISOTROPY AND POLARIZATION MEASUREMENTS WITH RATAN-600 ». International Journal of Modern Physics D 08, no 05 (octobre 1999) : 581–605. http://dx.doi.org/10.1142/s0218271899000407.
Texte intégralRésumé :
Some aspects of the Cosmological Gene project and the possibilities of the measurements of the Cosmic Microwave Background (CMB) anisotropy and polarization using the radio-telescope RATAN-600 (Special Astrophysical Observatory) are discussed. We study different strategies of the measurements and present main parameters of the antenna beam for these strategies at the frequency diapason ν=1–30 GHz. We simulate Cosmological Gene observations using a standard Cold Dark Matter cosmological model. We quantify the distortions of the primordial CMB-signal in the RATAN-600 scans by the atmosphere emission, foreground and noise in RATAN-600 scans. We emphasize that RATAN-600 is the unique instrument which allows the investigation of anisotropy and polarization of the CMB and investigate foreground and noise up to the multipole numbers l ∝ 105.
45
Welsch, Benoît, Emily C. First, Philipp Ruprecht et Michael C. Jollands. « Olivine—The Little Green Science Machine ». Elements 19, no 3 (1 juin 2023) : 138–43. http://dx.doi.org/10.2138/gselements.19.3.138.
Texte intégralRésumé :
In some ways, olivine has driven the evolution of the Solar System and likely beyond. As one of the earliest-crystallizing silicate minerals, olivine controls the initial chemical evolution of planet-wide magma oceans and individual lava flows alike. In solid aggregate form, it controls and records deformation of the mantle and smaller-scale intrusive complexes. The components of its crystal structure are mobile at high temperatures and their migration can be used to explore the timing of magmatic events. During chemical weathering, these olivine crystals capture carbon dioxide from the atmosphere as secondary minerals are formed. All of these processes take place not only on Earth, but also on other planetary bodies, making olivine ideally suited to shed light on both primordial planet-building processes and current-day volcanism and surface processes.
46
Rogers, James G., et James E. Owen. « Unveiling the planet population at birth ». Monthly Notices of the Royal Astronomical Society 503, no 1 (24 février 2021) : 1526–42. http://dx.doi.org/10.1093/mnras/stab529.
Texte intégralRésumé :
ABSTRACT The radius distribution of small, close-in exoplanets has recently been shown to be bimodal. The photoevaporation model predicted this bimodality. In the photoevaporation scenario, some planets are completely stripped of their primordial H/He atmospheres, whereas others retain them. Comparisons between the photoevaporation model and observed planetary populations have the power to unveil details of the planet population inaccessible by standard observations, such as the core mass distribution and core composition. In this work, we present a hierarchical inference analysis on the distribution of close-in exoplanets using forward models of photoevaporation evolution. We use this model to constrain the planetary distributions for core composition, core mass, and initial atmospheric mass fraction. We find that the core-mass distribution is peaked, with a peak-mass of ∼4M⊕. The bulk core-composition is consistent with a rock/iron mixture that is ice-poor and ‘Earth-like’; the spread in core-composition is found to be narrow ($\lesssim 16{{\ \rm per\ cent}}$ variation in iron-mass fraction at the 2σ level) and consistent with zero. This result favours core formation in a water/ice poor environment. We find the majority of planets accreted a H/He envelope with a typical mass fraction of $\sim 4{{\ \rm per\ cent}}$; only a small fraction did not accrete large amounts of H/He and were ‘born-rocky’. We find four times as many super-Earths were formed through photoevaporation, as formed without a large H/He atmosphere. Finally, we find core-accretion theory overpredicts the amount of H/He cores would have accreted by a factor of ∼5, pointing to additional mass-loss mechanisms (e.g. ‘boil-off’) or modifications to core-accretion theory.
47
Saito, Hiroaki, et Kiyoshi Kuramoto. « Volatile Mass Partitioned among the Atmosphere, Mantle, and Core in Proto-Mars ». Astrophysical Journal 969, no 2 (1 juillet 2024) : 158. http://dx.doi.org/10.3847/1538-4357/ad4ece.
Texte intégralRésumé :
Abstract We analyze the distribution of volatiles such as water, hydrogen, and carbon within the atmosphere, mantle, and core of Mars during its accretion stages. The partitioning of these volatiles is crucial as it influences the generation of intrinsic magnetic fields, mantle convection, and magmatic activity. The study suggests that the accretion process is responsible for the presence of water and light elements within the Martian mantle and core. We employ a hybrid-type proto-atmosphere model, which considers an upper layer composed of nebula components and a lower layer made up of degassed components from the impact degassing of the simplified building blocks based on the two-component model. Our numerical analysis implies that the formation of a magma ocean at this high temperature and pressure after around the half-size of the present Mars triggers the migration of water vapor, carbon, and hydrogen from the primordial atmosphere into the planetary interior. Ultimately, several 1021 kg of water could have been distributed to the mantle and, if degassed again by the formation of flood basalts on the Tharsis Plateau, could have supplied Mars’ ancient oceans. Meanwhile, several 1020 kg of carbon and 1019 kg of hydrogen (equivalent to 1020 kg H2O) were found to be distributed in the core. Although the distribution of sulfur was simplified so that all of the sulfur is in the core, a result of sulfur accounting for 14 wt% to 19 wt.% of the core mass would be consistent with the core density suggested by InSight.
48
Alba, Elisiane, Juliana Marchesan, Mateus Sabadi Schuh, José Augusto Spiazzi Favarin, Emanuel Araújo Silva et Rudiney Soares Pereira. « INFLUENCE OF FOREST COVERAGE IN THE SURFACE ALBEDO ». FLORESTA 50, no 1 (20 décembre 2019) : 1011. http://dx.doi.org/10.5380/rf.v50i1.60595.
Texte intégralRésumé :
The surface albedo controls the energy balance between the surface and the atmosphere, being a primordial variable to identify climatic variations. The objective of this study was to evaluate the changes of the surface albedo in different Land Use and Land Cover in the Atlantic Forest biome from images TM/Landsat 5 and OLI/Landsat 8, verifying its variation in 30 years. The images used were path-row 221-080, which covered the Floresta Nacional de São Francisco de Paula on the dates of 1987 and 2017. The albedo was obtained by the method of the Surface Energy Balance Algorithm for Land, while the mapping of Land Use and Land Cover was performed by the Bhattacharyya algorithm, identifying four thematic classes. Finally, the albedo was crossed with the thematic classes, evidencing their variation in function of the changes in the land cover. The surface albedo ranged from 6 to 22%, but the year 1987 concentrated albedo values higher than in 2017. The native forest presented superior albedo to the Forest Plantations in both dates due to the structure of the canopy of this class. The spatial analysis of the albedo exposes the relation of this climatic variable to the cover of the terrestrial surface. Thus changes in the vegetation cover cause alterations in the albedo, influencing changes in the radiation and atmospheric fluxes.
49
Thiel, Joana, James M. Byrne, Andreas Kappler, Bernhard Schink et Michael Pester. « Pyrite formation from FeS and H2S is mediated through microbial redox activity ». Proceedings of the National Academy of Sciences 116, no 14 (18 mars 2019) : 6897–902. http://dx.doi.org/10.1073/pnas.1814412116.
Texte intégralRésumé :
The exergonic reaction of FeS with H2S to form FeS2(pyrite) and H2was postulated to have operated as an early form of energy metabolism on primordial Earth. Since the Archean, sedimentary pyrite formation has played a major role in the global iron and sulfur cycles, with direct impact on the redox chemistry of the atmosphere. However, the mechanism of sedimentary pyrite formation is still being debated. We present microbial enrichment cultures which grew with FeS, H2S, and CO2as their sole substrates to produce FeS2and CH4. Cultures grew over periods of 3 to 8 mo to cell densities of up to 2 to 9 × 106cells per mL−1. Transformation of FeS with H2S to FeS2was followed by57Fe Mössbauer spectroscopy and showed a clear biological temperature profile with maximum activity at 28 °C and decreasing activities toward 4 °C and 60 °C. CH4was formed concomitantly with FeS2and exhibited the same temperature dependence. Addition of either penicillin or 2-bromoethanesulfonate inhibited both FeS2and CH4production, indicating a coupling of overall pyrite formation to methanogenesis. This hypothesis was supported by a 16S rRNA gene-based phylogenetic analysis, which identified at least one archaeal and five bacterial species. The archaeon was closely related to the hydrogenotrophic methanogenMethanospirillum stamsii, while the bacteria were most closely related to sulfate-reducing Deltaproteobacteria, as well as uncultured Firmicutes and Actinobacteria. Our results show that pyrite formation can be mediated at ambient temperature through a microbially catalyzed redox process, which may serve as a model for a postulated primordial iron−sulfur world.
50
Fu, Xiaoting, Alessandro Bressan, Paolo Molaro et Paola Marigo. « Lithium evolution from Pre-Main Sequence to the Spite plateau : an environmental solution to the cosmological lithium problem ». Proceedings of the International Astronomical Union 11, S317 (août 2015) : 300–301. http://dx.doi.org/10.1017/s1743921315007073.
Texte intégralRésumé :
AbstractLithium abundance derived in metal-poor main sequence stars is about three times lower than the primordial value of the standard Big Bang nucleosynthesis prediction. This disagreement is referred to as the lithium problem. We reconsider the stellar Li evolution from the pre-main sequence to the end of main sequence phase by introducing the effects of overshooting and residual mass accretion. We show that 7Li could be significantly depleted by convective overshooting in the pre-main sequence phase and then partially restored in the stellar atmosphere by residual accretion which follows the Li depletion phase and could be regulated by EUV photo-evaporation. By considering the conventional nuclear burning and diffusion along the main sequence we can reproduce the Spite plateau for stars with initial mass m0=0.62–0.80 M⊙, and the Li declining branch for lower mass dwarfs, e.g, m0=0.57–0.60 M⊙, for a wide range of metallicities (Z=0.00001 to Z=0.0005), starting from an initial Li abundance A(Li) = 2.72.