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1
Miller-Ricci, Eliza, Sara Seager und Dimitar Sasselov. „The Atmospheres of Extrasolar Super-Earths“. Proceedings of the International Astronomical Union 4, S253 (Mai 2008): 263–71. http://dx.doi.org/10.1017/s1743921308026483.
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AbstractExtrasolar super-Earths (1-10 M⊕) are likely to exist with a wide range of atmospheres. While a number of these planets have already been discovered through radial velocities and microlensing, it will be the discovery of the firsttransitingsuper-Earths that will open the door to a variety of follow-up observations aimed at characterizing their atmospheres. Super-Earths may fill a large range of parameter space in terms of their atmospheric composition and mass. Specifically, some of these planets may have high enough surface gravities to be able to retain large hydrogen-rich atmosphseres, while others will have lost most of their hydrogen to space over the planet's lifetime, leaving behind an atmosphere more closely resembling that of Earth or Venus. The resulting composition of the super-Earth atmosphere will therefore depend strongly on factors such as atmospheric escape history, outgassing history, and the level of stellar irradiation that it receives. Here we present theoretical models of super-Earth emission and transmission spectra for a variety of possible outcomes of super-Earth atmospheric composition ranging from hydrogen-rich to hydrogen-poor. We focus on how observations can be used to differentiate between the various scenarios and constrain atmospheric composition.
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Kempton, Eliza M. R. „The properties of super-Earth atmospheres“. Proceedings of the International Astronomical Union 6, S276 (Oktober 2010): 212–17. http://dx.doi.org/10.1017/s1743921311020205.
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AbstractExtrasolar super-Earths likely have a far greater diversity in their atmospheric properties than giant planets. Super-Earths (planets with masses between 1 and 10 M⊕) lie in an intermediate mass regime between gas/ice giants like Neptune and rocky terrestrial planets like Earth and Venus. While some super-Earths (especially the more massive ones) may retain large amounts of hydrogen either from accretion processes or subsequent surface outgassing, other super-Earths should have atmospheres composed of predominantly heavier molecules, similar to the atmospheres of the rocky planets and moons of our Solar System. Others still may be entirely stripped of their atmospheres and remain as bare rocky cores. Of the two currently known transiting super-Earths one (GJ 1214b) likely falls into the former category with a thick atmosphere, while the other (CoRoT-7b) falls into the latter category with a very thin or nonexistent atmosphere. I review some of the theoretical work on super-Earth atmospheres, and I present methods for determining the bulk composition of a super-Earth atmosphere.
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Kimura, Tadahiro, und 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, Nr. 3 (22.06.2020): 3755–66. http://dx.doi.org/10.1093/mnras/staa1778.
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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.
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Madhusudhan, Nikku, und Seth Redfield. „Optimal measures for characterizing water-rich super-Earths“. International Journal of Astrobiology 14, Nr. 2 (29.10.2014): 177–89. http://dx.doi.org/10.1017/s1473550414000421.
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AbstractThe detection and atmospheric characterization of super-Earths is one of the major frontiers of exoplanetary science. Currently, extensive efforts are underway to detect molecules, particularly H2O, in super-Earth atmospheres. In the present work, we develop a systematic set of strategies to identify and observe potentially H2O-rich super-Earths that provide the best prospects for characterizing their atmospheres using existing instruments. First, we provide analytic prescriptions and discuss factors that need to be taken into account while planning and interpreting observations of super-Earth radii and spectra. We discuss how observations in different spectral bandpasses constrain different atmospheric properties of a super-Earth, including radius and temperature of the planetary surface as well as the mean molecular mass, the chemical composition and thermal profile of the atmosphere. In particular, we caution that radii measured in certain bandpasses can induce biases in the interpretation of the interior compositions. Second, we investigate the detectability of H2O-rich super-Earth atmospheres using the Hubble Space Telescope Wide Field Camera 3 spectrograph as a function of the planetary properties and stellar brightness. We find that highly irradiated super-Earths orbiting bright stars, such as 55 Cancri e, present better candidates for atmospheric characterization compared to cooler planets such as GJ 1214b even if the latter orbit lower-mass stars. Besides being better candidates for both transmission and emission spectroscopy, hotter planets offer higher likelihood of cloud-free atmospheres which aid tremendously in the observation and interpretation of spectra. Finally, we present case studies of two super-Earths, GJ 1214b and 55 Cancri e, using available data and models of their interiors and atmospheres.
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Claudi, R., M. S. Erculiani, G. Galletta, D. Billi, E. Pace, D. Schierano, E. Giro und M. D'Alessandro. „Simulating super earth atmospheres in the laboratory“. International Journal of Astrobiology 15, Nr. 1 (20.05.2015): 35–44. http://dx.doi.org/10.1017/s1473550415000117.
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AbstractSeveral space missions, such as JWST, TESS and the very recently proposed ARIEL, or ground-based experiments, as SPHERE and GPI, have been proposed to measure the atmospheric transmission, reflection and emission spectra of extrasolar planets. The planet atmosphere characteristics and possible biosignatures will be inferred by studying planetary spectra in order to identify the emission/absorption lines/bands from atmospheric molecules such as water (H2O), carbon monoxide (CO), methane (CH4), ammonia (NH3), etc. In particular, it is important to know in detail the optical characteristics of gases in the typical physical conditions of the planetary atmospheres and how these characteristics could be affected by radiation driven photochemical and biochemical reaction. The main aim of the project ‘Atmosphere in a Test Tube’ is to provide insights on exoplanet atmosphere modification due to biological intervention. This can be achieved simulating planetary atmosphere at different pressure and temperature conditions under the effects of radiation sources, used as proxies of different bands of the stellar emission. We are tackling the characterization of extrasolar planet atmospheres by mean of innovative laboratory experiments described in this paper. The experiments are intended to reproduce the conditions on warm earths and super earths hosted by low-mass M dwarfs primaries with the aim to understand if a cyanobacteria population hosted on a Earth-like planet orbiting an M0 star is able to maintain its photosynthetic activity and produce traceable signatures.
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Kurosaki, Kenji, und Shu-ichiro Inutsuka. „Giant Impact Events for Protoplanets: Energetics of Atmospheric Erosion by Head-on Collision“. Astrophysical Journal 954, Nr. 2 (01.09.2023): 196. http://dx.doi.org/10.3847/1538-4357/ace9ba.
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Abstract Numerous exoplanets with masses ranging from Earth to Neptune and radii larger than Earth have been found through observations. These planets possess atmospheres that range in mass fractions from 1% to 30%, reflecting the diversity of atmospheric mass fractions. Such diversities are supposed to be caused by differences in the formation processes or evolution. Here, we consider head-on giant impacts onto planets causing atmosphere losses in the later stage of their formation. We perform smoothed particle hydrodynamic simulations to study the impact-induced atmosphere loss of young super-Earths with 10%–30% initial atmospheric mass fractions. We find that the kinetic energy of the escaping atmosphere is almost proportional to the sum of the kinetic impact energy and self-gravitational energy released from the merged core. We derive the relationship between the kinetic impact energy and the escaping atmosphere mass. The giant impact events for planets of comparable masses are required in the final stage of the popular scenario of rocky planet formation. We show it results in a significant loss of the atmosphere, if the impact is a head-on collision with comparable masses. This latter fact provides a constraint on the formation scenario of rocky planets with substantial atmospheres.
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Zilinskas, Mantas, Yamila Miguel, Paul Mollière und Shang-Min Tsai. „Atmospheric compositions and observability of nitrogen-dominated ultra-short-period super-Earths“. Monthly Notices of the Royal Astronomical Society 494, Nr. 1 (14.03.2020): 1490–506. http://dx.doi.org/10.1093/mnras/staa724.
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ABSTRACT We explore the chemistry and observability of nitrogen-dominated atmospheres for ultra-short-period super-Earths. We base the assumption that super-Earths could have nitrogen-filled atmospheres on observations of 55 Cancri e that favour a scenario with a high-mean-molecular-weight atmosphere. We take Titan’s elemental budget as our starting point and using chemical kinetics compute a large range of possible compositions for a hot super-Earth. We use analytical temperature profiles and explore a parameter space spanning orders of magnitude in C/O and N/O ratios, while always keeping nitrogen the dominant component. We generate synthetic transmission and emission spectra and assess their potential observability with the future James Webb Space Telescope (JWST) and ARIEL. Our results suggest that HCN is a strong indicator of a high C/O ratio, which is similar to what is found for H-dominated atmospheres. We find that these worlds are likely to possess C/O > 1.0, and that HCN, CN, and CO should be the primary molecules to be searched for in thermal emission. For lower temperatures (T < 1500 K), we additionally find NH3 in high N/O ratio cases, and C2H4 and CH4 in low N/O ratio cases to be strong absorbers. Depletion of hydrogen in such atmospheres would make CN, CO, and NO exceptionally prominent molecules to look for in the 0.6–5.0 $\rm{\mu m}$ range. Our models show that the upcoming JWST and ARIEL missions will be able to distinguish atmospheric compositions of ultra-short-period super-Earths with unprecedented confidence.
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Kaltenegger, L. „Biomarkers of Habitable Worlds - Super-Earths and Earths“. Proceedings of the International Astronomical Union 7, S280 (Juni 2011): 302–12. http://dx.doi.org/10.1017/s1743921311025063.
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AbstractA decade of exoplanet search has led to surprising discoveries, from giant planets close to their star, to planets orbiting two stars, all the way to the first extremely hot, rocky worlds with potentially permanent lava on their surfaces due to the star's proximity. Observation techniques have reached the sensitivity to explore the chemical composition of the atmospheres as well as physical structure of some detected planets. Recent advances in detection techniques find planets of less than 10 MEarth (so called Super-Earths), among them some that may potentially be habitable. Two confirmed non-transiting planets and several transiting Kepler planetary candidates orbit in the Habitable Zone of their host star. The detection and characterization of rocky and potentially Earth-like planets is approaching rapidly with future ground- and space-missions, that can explore the planetary environments by analyzing their atmosphere remotely. The results of a first generation space mission will most likely be an amazing scope of diverse planets that will set planet formation, evolution as well as our planet in an overall context.
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Misener, William, und 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, Nr. 4 (27.03.2021): 5658–74. http://dx.doi.org/10.1093/mnras/stab895.
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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.
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Fujita, Naho, Yasunori Hori und Takanori Sasaki. „Orbital Evolution of Close-in Super-Earths Driven by Atmospheric Escape“. Astrophysical Journal 928, Nr. 2 (30.03.2022): 105. http://dx.doi.org/10.3847/1538-4357/ac558c.
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Abstract The increasing number of super-Earths close to their host stars have revealed a scarcity of close-in small planets with 1.5–2.0 R ⊕ in the radius distribution of Kepler planets. The atmospheric escape of super-Earths by photoevaporation can explain the origin of the observed “radius gap.” Many theoretical studies have considered the in situ mass loss of a close-in planet. Planets that undergo atmospheric escape, however, move outward due to the change in the orbital angular momentum of their star–planet systems. In this study, we calculate the orbital evolution of an evaporating super-Earth with a H2/He atmosphere around FGKM-type stars under stellar X-ray and extreme-UV irradiation (XUV). The rate of increase in the orbital radius of an evaporating planet is approximately proportional to that of the atmospheric mass loss during a high stellar XUV phase. We show that super-Earths with a rocky core of ≲10 M ⊕ and a H2/He atmosphere at ≲0.03–0.1 au (≲0.01–0.03 au) around G-type stars (M-type stars) are prone to outward migration driven by photoevaporation. Although the changes in the orbits of the planets would be small, they would rearrange the orbital configurations of compact, multiplanet systems, such as the TRAPPIST-1 system. We also find that the radius gap and the so-called “Neptune desert” in the observed population of close-in planets around FGK-type stars still appear in our simulations. On the other hand, the observed planet population around M-type stars can be reproduced only by a high stellar XUV luminosity model.
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Kaltenegger, Lisa, Antígona Segura und Subhanjoy Mohanty. „Super-Earths and life - a fascinating puzzle: Example GJ 581d“. Proceedings of the International Astronomical Union 6, S276 (Oktober 2010): 376–84. http://dx.doi.org/10.1017/s1743921311020461.
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AbstractSpurred by the recent large number of radial velocity detections and the discovery of several transiting system and among those two planets, that are consistent with rocky composition, the study of planets orbiting nearby stars has now entered an era of characterizing massive terrestrial planets (aka super-Earths). One prominent question is, if such planets could be habitats. Here we focuss on one particular planet Gl581d. For Earth-like assumptions, we investigate the minimal atmospheric conditions for Gl581d to be potentially habitable at its current position, and if habitability could be remotely detected in its spectra. The model we present here only represents one possible nature an Earth-like composition - of a planet like Gl581d in a wide parameter space. Future observations of atmospheric features of such super-Earths can be used to examine if our concept of habitability and its dependence on the carbonate-silicate cycle is correct, and also assess whether Gl581d is indeed the first detected habitable super-Earth. We will need spectroscopic measurements to probe the atmosphere of such planets to break the degeneracy of mass and radius measurements and characterize a planetary environment.
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Schultz, David M., Jonathan G. Fairman, Stuart Anderson und Sharon Gardner. „Build Your Own Earth: A Web-Based Tool for Exploring Climate Model Output in Teaching and Research“. Bulletin of the American Meteorological Society 98, Nr. 8 (01.08.2017): 1617–23. http://dx.doi.org/10.1175/bams-d-16-0121.1.
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Abstract Build Your Own Earth was designed as a web-based tool for the user to select various characteristics of a planet and see what the climate of that planet would be like. Because of the limitations of computer resources, presimulated Earths were run using the Fast Ocean Atmosphere Model at relatively coarse resolution. The tool provides 50 different Earth configurations in three categories: Recent, Ancient, and Alien Earths. Recent Earths fix the continental configuration at the present day and vary the axial tilt, eccentricity, and greenhouse gas concentrations. Ancient Earths include a series of paleoclimate simulations from the Last Glacial Maximum 21,000 years ago to the Ediacaran 600 million years ago. Alien Earths include an aquaplanet, terraplanet, ice planet, and various idealized continental configurations. Fifty different monthly averaged quantities are available to view in an annual cycle from four different map projections. Build Your Own Earth was built and designed for a massive open online course, but it has also been used in the classroom at the University of Manchester, as well as research projects on paleoclimate and planetary habitability, for example. The tool is freely available online (www.buildyourownearth.com) for anyone to access.
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Venturini, Julia, Octavio Miguel Guilera, María Paula Ronco und Christoph Mordasini. „Most super-Earths formed by dry pebble accretion are less massive than 5 Earth masses“. Astronomy & Astrophysics 644 (Dezember 2020): A174. http://dx.doi.org/10.1051/0004-6361/202039140.
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Aims. The goal of this work is to study the formation of rocky planets by dry pebble accretion from self-consistent dust-growth models. In particular, we aim to compute the maximum core mass of a rocky planet that can sustain a thin H-He atmosphere to account for the second peak of the Kepler size distribution. Methods. We simulate planetary growth by pebble accretion inside the ice line. The pebble flux is computed self-consistently from dust growth by solving the advection–diffusion equation for a representative dust size. Dust coagulation, drift, fragmentation, and sublimation at the water ice line are included. The disc evolution is computed solving the vertical and radial structure for standard α-discs with photoevaporation from the central star. The planets grow from a moon-mass embryo by silicate pebble accretion and gas accretion. We perform a parameter study to analyse the effect of a different initial disc mass, α-viscosity, disc metallicity, and embryo location. We also test the effect of considering migration versus an in situ scenario. Finally, we compute atmospheric mass loss due to evaporation over 5 Gyr of evolution. Results. We find that inside the ice line, the fragmentation barrier determines the size of pebbles, which leads to different planetary growth patterns for different disc viscosities. We also find that in this inner disc region, the pebble isolation mass typically decays to values below 5 M⊕ within the first million years of disc evolution, limiting the core masses to that value. After computing atmospheric mass loss, we find that planets with cores below ~4 M⊕ become completely stripped of their atmospheres, and a few 4–5 M⊕ cores retain a thin atmosphere that places them in the “gap” or second peak of the Kepler size distribution. In addition, a few rare objects that form in extremely low-viscosity discs accrete a core of 7 M⊕ and equal envelope mass, which is reduced to 3–5 M⊕ after evaporation. These objects end up with radii of ~6–7 R⊕. Conclusions. Overall, we find that rocky planets form only in low-viscosity discs (α ≲ 10−4). When α ≥ 10−3, rocky objects do not grow beyond 1 Mars mass. For the successful low-viscosity cases, the most typical outcome of dry pebble accretion is terrestrial planets with masses spanning from that of Mars to ~4 M⊕.
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Dumusque, Xavier. „The SCORE project: finding Earth 2.0 Does life exist elsewhere in the Universe?“ Project Repository Journal 13, Nr. 1 (07.05.2022): 74–77. http://dx.doi.org/10.54050/prj1318814.
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The SCORE project: finding Earth 2.0 Does life exist elsewhere in the Universe? The goal of the SCORE project is to enable the detection of other Earths orbiting bright, close-by Sun-like stars for which future ground and space-based missions will be able to characterise their atmosphere in the search for signatures of life elsewhere in the Universe.
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Karacaoglu, Erkul, Bekir Karasu und Esra Öztürk. „The Investigations on Luminescence Characteristics and Influence of Doping and Co-Doping Different Rare Earth Ions in White Phosphorescence Materials Having Different Luminescent Centers“. Advances in Science and Technology 90 (Oktober 2014): 133–40. http://dx.doi.org/10.4028/www.scientific.net/ast.90.133.
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The Akermanite type alkaline earth silicate Ca2MgSi2O7 activated by different types of rare earths was prepared by the conventional solid state reaction method under weak reductive atmosphere. The phase formation, particle size distribution, particle morphologies and photoluminescence properties of the samples have been investigated respectively. The comparative results of SEM and laser particle size analysis revealed that the relatively regular morphology, smaller particle size distribution could be achieved for the phosphors synthesized by the solid state reaction method including dry-ground after which powders were sieved below 170 meshes. The effects of rare earth oxides; Nd2O3, Pr6O11, Ce2O3 and Sm2O3 on the luminescence properties of the host material, Ca2MgSi2O7, were studied. Remarkable enhancement and novel color emitting including white in luminescence characteristics of host material were observed as a result of doping the mentioned rare-earths were doped.
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Denman, Thomas R., Zoe M. Leinhardt, Philip J. Carter und Christoph Mordasini. „Atmosphere loss in planet–planet collisions“. Monthly Notices of the Royal Astronomical Society 496, Nr. 2 (17.06.2020): 1166–81. http://dx.doi.org/10.1093/mnras/staa1623.
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ABSTRACT Many of the planets discovered by the Kepler satellite are close orbiting super-Earths or mini-Neptunes. Such objects exhibit a wide spread of densities for similar masses. One possible explanation for this density spread is giant collisions stripping planets of their atmospheres. In this paper, we present the results from a series of smoothed particle hydrodynamics (sph) simulations of head-on collisions of planets with significant atmospheres and bare projectiles without atmospheres. Collisions between planets can have sufficient energy to remove substantial fractions of the mass from the target planet. We find the fraction of mass lost splits into two regimes – at low impact energies only the outer layers are ejected corresponding to atmosphere dominated loss, at higher energies material deeper in the potential is excavated resulting in significant core and mantle loss. Mass removal is less efficient in the atmosphere loss dominated regime compared to the core and mantle loss regime, due to the higher compressibility of atmosphere relative to core and mantle. We find roughly 20 per cent atmosphere remains at the transition between the two regimes. We find that the specific energy of this transition scales linearly with the ratio of projectile to target mass for all projectile-target mass ratios measured. The fraction of atmosphere lost is well approximated by a quadratic in terms of the ratio of specific energy and transition energy. We provide algorithms for the incorporation of our scaling law into future numerical studies.
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Boccaletti, Anthony, Alessandro Sozzetti, Jean Schneider, Pierre Baudoz, Giovanna Tinetti und Daphne Stam. „The SEE-COAST concept“. Proceedings of the International Astronomical Union 5, H15 (November 2009): 718–19. http://dx.doi.org/10.1017/s1743921310011154.
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AbstractThe SEE COAST concept is designed with the objective to characterize extrasolar planets and possibly Super Earths via spectro-polarimetric imaging in reflected light. A space mission complementary to ground-based near IR planet finders is a first secure step towards the characterization of planets with mass and atmosphere comparable to that of the Earth. The accessibility to the Visible spectrum is unique and with important scientific returns.
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Huang, Jiang, Wei Zhong und Cong Yu. „Effects of Self-gravity on Mass-loss of the Post-impact Super-Earths“. Research in Astronomy and Astrophysics 22, Nr. 4 (17.03.2022): 045004. http://dx.doi.org/10.1088/1674-4527/ac501d.
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Abstract Kepler’s observations show most of the exoplanets are super-Earths. The formation of a super-Earth is generally related to the atmospheric mass loss that is crucial in the planetary structure and evolution. The shock driven by the giant impact will heat the planet, resulting in the atmosphere escape. We focus on whether self-gravity changes the efficiency of mass loss. Without self-gravity, if the impactor mass is comparable to the envelope mass, there is a significant mass-loss. The radiative-convective boundary will shift inward by self-gravity. As the temperature and envelope mass increase, the situation becomes more prominent, resulting in a heavier envelope. Therefore, the impactor mass will increase to motivate the significant mass loss, as the self-gravity is included. With the increase of envelope mass, the self-gravity is particularly important.
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Kaltenegger, L., Y. Miguel und S. Rugheimer. „Rocky exoplanet characterization and atmospheres“. International Journal of Astrobiology 11, Nr. 4 (16.02.2012): 297–307. http://dx.doi.org/10.1017/s1473550412000134.
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AbstractA decade of exoplanet search has led to surprising discoveries, from giant planets close to their star, to planets orbiting two stars, all the way to the first extremely hot, rocky worlds with potentially permanent lava on their surfaces due to the star's proximity. Observation techniques have reached the sensitivity to explore the chemical composition of the atmospheres as well as physical structure of some detected gas planets and detect planets of less than 10 Earth masses (MEarth), the so-called super-Earths, among them some that may potentially be habitable. Three confirmed non-transiting planets, and several transiting Kepler planetary candidates, orbit in the habitable zone (HZ) of their host star. The detection and characterization of rocky and potentially Earth-like planets is approaching rapidly with future ground and space missions that can explore the planetary environments by analysing their atmosphere remotely. This paper discusses how to characterize a rocky exoplanet remotely.
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Ullman, J. E., R. W. McCallum und J. D. Verhoeven. „Effect of atmosphere and rare earth on liquidus relations in RE–Ba–Cu Oxides“. Journal of Materials Research 4, Nr. 4 (August 1989): 752–54. http://dx.doi.org/10.1557/jmr.1989.0752.
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In the processing of the high temperature superconductors RE1Ba2Cu3O7−x a knowledge of the liquidus temperatures is required in order to avoid liquid formation during the initial reactions of the starting materials. We have investigated the invariant points on the liquidus surface of the RE–Ba–Cu–O systems for RE = Y, Er, Gd, and Nd in oxygen, air, and argon, While the temperatures of the low melting reactions are almost independent of the rare earth species, they are heavily dependent on oxygen partial pressure. In addition, the peritectic decomposition temperature of the REBa2Cu3O7 phase was found to be a function of rare earth with a significantly higher value for the Nd compound than for the other rare earths.
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Béthune, William, und Roman R. Rafikov. „Envelopes of embedded super-Earths – II. Three-dimensional isothermal simulations“. Monthly Notices of the Royal Astronomical Society 488, Nr. 2 (10.07.2019): 2365–79. http://dx.doi.org/10.1093/mnras/stz1870.
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ABSTRACT Massive planetary cores embedded in protoplanetary discs are believed to accrete extended atmospheres, providing a pathway to forming gas giants and gas-rich super-Earths. The properties of these atmospheres strongly depend on the nature of the coupling between the atmosphere and the surrounding disc. We examine the formation of gaseous envelopes around massive planetary cores via three-dimensional inviscid and isothermal hydrodynamic simulations. We focus the changes in the envelope properties as the core mass varies from low (subthermal) to high (superthermal) values, a regime relevant to close-in super-Earths. We show that global envelope properties such as the amount of rotational support or turbulent mixing are mostly sensitive to the ratio of the Bondi radius of the core to its physical size. High-mass cores are fed by supersonic inflows arriving along the polar axis and shocking on the densest parts of the envelope, driving turbulence, and mass accretion. Gas flows out of the core’s Hill sphere in the equatorial plane, describing a global mass circulation through the envelope. The shell of shocked gas atop the core surface delimits regions of slow (inside) and fast (outside) material recycling by gas from the surrounding disc. While recycling hinders the runaway growth towards gas giants, the inner regions of protoplanetary atmospheres, more immune to mixing, may remain bound to the planet.
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Zhong, Wei, und Cong Yu. „In Situ Formation of Super-Earth/Sub-Neptune Driven by the Planetary Rotation“. Astrophysical Journal 922, Nr. 2 (01.12.2021): 215. http://dx.doi.org/10.3847/1538-4357/ac2cc5.
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Abstract Kepler’s observation shows that many of the detected planets are super-Earths. They are inside a range of critical masses overlapping the core masses (2–20 M ⊕), which would trigger the runaway accretion and develop the gas giants. Thus, super-Earths/sub-Neptunes can be formed by restraining runaway growth of gaseous envelopes. We assess the effect of planetary rotation in delaying the mass growth. The centrifugal force, induced by spin, will offset a part of the gravitational force and deform the planet. Tracking the change in structure, we find that the temperature at the radiative–convective boundary (RCB) is approximate to the boundary temperature. Since rotation reduces the radiation energy densities in the convective and radiative layers, RCB will penetrate deeper. The cooling luminosity would decrease. Under this condition, the evolutionary timescale can exceed the disk lifetime (10 Myr), and a super-Earth/sub-Neptune could be formed after undergoing additional mass-loss processes. In the dusty atmosphere, even a lower angular velocity can also promote a super-Earth/sub-Neptune forming. Therefore, we conclude that rotation can slow down the planet’s cooling and then promote a super-Earth/sub-Neptune forming.
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Maire, Anne-Lise, Raphaël Galicher, Anthony Boccaletti, Pierre Baudoz, Jean Schneider, Kerri Cahoy, Daphne Stam und Wesley Traub. „Atmospheric Characterization of Cold Exoplanets Using a 1.5-m Space Coronagraph“. Proceedings of the International Astronomical Union 8, S293 (August 2012): 289–91. http://dx.doi.org/10.1017/s174392131301301x.
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AbstractWe present numerical results of the science performance of the SPICES mission, which aims to characterize the spectro-polarimetric properties of cold exoplanets and circumstellar disks in the visible. We focus on the instrument ability to retrieve the spectral signatures of molecular species, clouds and surface of super-Earths in the habitable zone of solar-type stars. Considering realistic reflected planet spectra and instrument limitation, we show that SPICES could analyse the atmosphere and surface of a few super-Earths within 5 pc of the Sun.
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Berni, L. A., L. E. A. Vieira, G. S. Savonov, A. Dal Lago, O. Mendes, M. R. Silva, F. Guarnieri et al. „Preliminary Design of the Brazilian's National Institute for Space Research Broadband Radiometer for Solar Observations“. Proceedings of the International Astronomical Union 12, S328 (Oktober 2016): 224–26. http://dx.doi.org/10.1017/s1743921317003866.
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AbstractThe Total Solar Irradiance (TSI), which is the total radiation arriving at Earth's atmosphere from the Sun, is one of the most important forcing of the Earths climate. Measurements of the TSI have been made employing instruments on board several space-based platforms during the last four solar cycles. However, combining these measurements is still challenging due to the degradation of the sensor elements and the long-term stability of the electronics. Here we describe the preliminary efforts to design an absolute radiometer based on the principle of electrical substitution that is under development at Brazilian's National Institute for Space Research (INPE).
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Bradley, John. „Water and organics in interplanetary dust particles“. Proceedings of the International Astronomical Union 11, A29B (August 2015): 420. http://dx.doi.org/10.1017/s174392131600569x.
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AbstractInterplanetary dust particles (IDPs) and larger micrometeorites (MMs) impinge on the upper atmosphere where they decelerate at 90 km altitude and settle to the Earths surface. Comets and asteroids are the major sources and the flux, 30,000-40,000 tons/yr, is comparable to the mass of larger meteorites impacting the Earths surface. The sedimentary record suggests that the flux was much higher on the early Earth. The chondritic porous (CP) subset of IDPs together with their larger counterparts, ultracarbonaceous micrometeorites (UCMMs), appear to be unique among known meteoritic materials in that they are composed almost exclusively of anhydrous minerals, some of them contain >> 50% organic carbon by volume as well as the highest abundances of presolar silicate grains including GEMS. D/H and 15N abundances implicate the Oort Cloud or presolar molecular cloud as likely sources of the organic carbon. Prior to atmospheric entry, IDPs and MMs spend 104-105 year lifetimes in solar orbit where their surfaces develop amorphous space weathered rims from exposure to the solar wind (SW). Similar rims are observed on lunar soil grains and on asteroid Itokawa regolith grains. Using valence electron energy-loss spectroscopy (VEELS) we have detected radiolytic water in the rims on IDPs formed by the interaction of solar wind protons with oxygen in silicate minerals. Therefore, IDPs and MMs continuously deliver both water and organics to the earth and other terrestrial planets. The interaction of protons with oxygen-rich minerals to form water is a universal process.
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Gordeev, E. I., S. N. Kulichkov, P. P. Firstov, O. E. Popov, I. P. Chunchuzov, D. I. Budilov und D. V. Chebrov. „Infrasonic waves and assessment of energy of explosion of Beringovomorsky meteoroid on December 19, 2018“. Доклады Академии наук 489, Nr. 4 (10.12.2019): 409–13. http://dx.doi.org/10.31857/s0869-56524894409-413.
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On December 18, 2018 at 23:48 UTC in the Earths atmosphere, at the height of 25,6 km over the Bering sea, destruction of a meteoroid with formation of a shockwave occurred. The mass of the Beringovomorsky meteoroid is estimated as 1600 tons, and its diameter is estimated as 9-14 meters. If assessment is right, then for the last 30 years it was the second in energy explosion of a space body in the Earths atmosphere. The nearest to the epicenter of meteoroid explosion station of the international system of infrasonic monitoring (IS44 station) is located on the Kamchatka peninsula at a distance of 1024 km. At IS44 station, an infrasonic signal from destruction of a meteoroid was registered. In this paper, the results of analysis of the infrasonic signal registered by IS44 are represented and the estimation of energy of this event is carried out.
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Tackley, Paul J., Michael M. Ammann, John P. Brodholt, David P. Dobson und Diana Valencia. „Habitable Planets: Interior Dynamics and Long-Term Evolution“. Proceedings of the International Astronomical Union 8, S293 (August 2012): 339–49. http://dx.doi.org/10.1017/s1743921313013136.
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AbstractHere, the state of our knowledge regarding the interior dynamics and evolution of habitable terrestrial planets including Earth and super-Earths is reviewed, and illustrated using state-of-the-art numerical models. Convection of the rocky mantle is the key process that drives the evolution of the interior: it causes plate tectonics, controls heat loss from the metallic core (which generates the magnetic field) and drives long-term volatile cycling between the atmosphere/ocean and interior. Geoscientists have been studying the dynamics and evolution of Earth's interior since the discovery of plate tectonics in the late 1960s and on many topics our understanding is very good, yet many first-order questions remain. It is commonly thought that plate tectonics is necessary for planetary habitability because of its role in long-term volatile cycles that regulate the surface environment. Plate tectonics is the surface manifestation of convection in the 2900-km deep rocky mantle, yet exactly how plate tectonics arises is still quite uncertain; other terrestrial planets like Venus and Mars instead have a stagnant lithosphere- essentially a single plate covering the entire planet. Nevertheless, simple scalings as well as more complex models indicate that plate tectonics should be easier on larger planets (super-Earths), other things being equal. The dynamics of terrestrial planets, both their surface tectonics and deep mantle dynamics, change over billions of years as a planet cools. Partial melting is a key process influencing solid planet evolution. Due to the very high pressure inside super-Earths' mantles the viscosity would normally be expected to be very high, as is also indicated by our density function theory (DFT) calculations. Feedback between internal heating, temperature and viscosity leads to a superadiabatic temperature profile and self-regulation of the mantle viscosity such that sluggish convection still occurs.
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Modirrousta-Galian, Darius, und Jun Korenaga. „The Three Regimes of Atmospheric Evaporation for Super-Earths and Sub-Neptunes“. Astrophysical Journal 943, Nr. 1 (01.01.2023): 11. http://dx.doi.org/10.3847/1538-4357/ac9d34.
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Abstract A significant fraction of super-Earths and sub-Neptunes are thought to experience an extreme loss of volatiles because of atmospheric evaporation in the early stages of their life. Though the mechanisms behind the extreme mass loss are not fully understood, two contenders have been widely discussed: photoevaporation from X-ray and ultraviolet irradiation and core-powered mass loss. Here, it is shown that both mechanisms occur, but with different timescales, and that atmospheric loss can take place over three regimes. In the first regime, a planet has very high internal temperatures arising from its high-energy formation processes. These high temperatures give rise to a fully convecting atmosphere that efficiently loses mass without much internal cooling. The second regime applies to planets with lower internal temperatures, so a radiative region forms, but the photosphere still remains outside the Bondi radius. Hence, mass loss continues to depend only on the internal temperatures. Planets with the lowest internal temperatures are in the third regime, when the photosphere forms below the Bondi radius and mass is lost primarily because of X-ray and ultraviolet irradiation. This paper provides the first unifying framework for modeling atmospheric evaporation through the life span of a planet.
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Horn, H. W., V. Prakapenka, S. Chariton, S. Speziale und S. H. Shim. „Reaction between Hydrogen and Ferrous/Ferric Oxides at High Pressures and High Temperatures—Implications for Sub-Neptunes and Super-Earths“. Planetary Science Journal 4, Nr. 2 (01.02.2023): 30. http://dx.doi.org/10.3847/psj/acab03.
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Abstract Sub-Neptune exoplanets may have thick hydrogen envelopes and therefore develop a high-pressure interface between hydrogen and the underlying silicates/metals. Some sub-Neptunes may convert to super-Earths via massive gas loss. If hydrogen chemically reacts with oxides and metals at high pressures and temperatures (P−T), it could impact the structure and composition of the cores and atmospheres of sub-Neptunes and super-Earths. While H2 gas is a strong reducing agent at low pressures, the behavior of hydrogen is unknown at the P−T expected for sub-Neptunes’ interiors, where hydrogen is a dense supercritical fluid. Here we report experimental results of reactions between ferrous/ferric oxides and hydrogen at 20–40 GPa and 1000–4000 K utilizing the pulsed laser-heated diamond-anvil cell combined with synchrotron X-ray diffraction. Under these conditions, hydrogen spontaneously strips iron off the oxides, forming Fe-H alloys and releasing oxygen to the hydrogen medium. In a planetary context where this reaction may occur, the Fe-H alloy may sink to the metallic part of the core, while released oxygen may stabilize as water in the silicate layer, providing a mechanism to ingas hydrogen to the deep interiors of sub-Neptunes. Water produced from the redox reaction can also partition to the atmosphere of sub-Neptunes, which has important implications for understanding the composition of their atmospheres. In addition, super-Earths converted from sub-Neptunes may contain a large amount of hydrogen and water in their interiors (at least a few wt% H2O). This is distinct from smaller rocky planets, which were formed relatively dry (likely a few hundredths wt% H2O).
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Bonfanti, A., L. Fossati, D. Kubyshkina und P. E. Cubillos. „Constraining stellar rotation and planetary atmospheric evolution of a dozen systems hosting sub-Neptunes and super-Earths“. Astronomy & Astrophysics 656 (Dezember 2021): A157. http://dx.doi.org/10.1051/0004-6361/202142010.
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Context. Planetary atmospheric evolution modelling is a prime tool for understanding the observed exoplanet population and constraining formation and migration mechanisms, but it can also be used to study the evolution of the activity level of planet hosts. Aims. We constrain the planetary atmospheric mass fraction at the time of the dispersal of the protoplanetary disk and the evolution of the stellar rotation rate for a dozen multi-planet systems that host sub-Neptunes and/or super-Earths. Methods. We employ a custom-developed PYTHON code that we have dubbed PASTA (Planetary Atmospheres and Stellar RoTation RAtes), which runs within a Bayesian framework to model the atmospheric evolution of exoplanets. The code combines MESA stellar evolutionary tracks, a model describing planetary structures, a model relating stellar rotation and activity level, and a model predicting planetary atmospheric mass-loss rates based on the results of hydrodynamic simulations. Results. Through a Markov chain Monte Carlo scheme, we retrieved the posterior probability density functions of all considered parameters. For ages older than about 2 Gyr, we find a median spin-down (i.e. P(t)∝ty) of ȳ = 0.38−0.27+0.38, indicating a rotation decay slightly slower than classical literature values (≈0.5), though still within 1σ. At younger ages, we find a median spin-down (i.e. P(t)∝tx) of x̄ = 0.26−0.19+0.42, which is below what is observed in young open clusters, though within 1σ. Furthermore, we find that the x probability distribution we derived is skewed towards lower spin-down rates. However, these two results are likely due to a selection bias as the systems suitable to be analysed by PASTA contain at least one planet with a hydrogen-dominated atmosphere, implying that the host star has more likely evolved as a slow rotator. We further look for correlations between the initial atmospheric mass fraction of the considered planets and system parameters (i.e. semi-major axis, stellar mass, and planetary mass) that would constrain planetary atmospheric accretion models, but without finding any. Conclusions. PASTA has the potential to provide constraints to planetary atmospheric accretion models, particularly when considering warm sub-Neptunes that are less susceptible to mass loss compared to hotter and/or lower-mass planets. The TESS, CHEOPS, and PLATO missions are going to be instrumental in identifying and precisely measuring systems amenable to PASTA’s analysis and can thus potentially constrain planet formation and stellar evolution.
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Cuartas-Restrepo, Pablo. „Planetary Magnetic Fields and Habitability in Super Earths“. Open Astronomy 27, Nr. 1 (01.09.2018): 183–231. http://dx.doi.org/10.1515/astro-2018-0026.
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Abstract This work seeks to summarize some special aspects of a type of exoplanets known as super-Earths (SE), and the direct influence of these aspects in their habitability. Physical processes like the internal thermal evolution and the generation of a protective Planetary Magnetic Field (PMF) are directly related with habitability. Other aspects such as rotation and the formation of a solid core are fundamental when analyzing the possibilities that a SE would have to be habitable. This work analyzes the fundamental theoretical aspects on which the models of thermal evolution and the scaling laws of the planetary dynamos are based. These theoretical aspects allow to develop models of the magnetic evolution of the planets and the role played by the PMF in the protection of the atmosphere and the habitability of the planet.
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Lambrechts, Michiel, Alessandro Morbidelli, Seth A. Jacobson, Anders Johansen, Bertram Bitsch, Andre Izidoro und Sean N. Raymond. „Formation of planetary systems by pebble accretion and migration“. Astronomy & Astrophysics 627 (Juli 2019): A83. http://dx.doi.org/10.1051/0004-6361/201834229.
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Super-Earths – planets with sizes between the Earth and Neptune – are found in tighter orbits than that of the Earth around more than one third of main sequence stars. It has been proposed that super-Earths are scaled-up terrestrial planets that also formed similarly, through mutual accretion of planetary embryos, but in discs much denser than the solar protoplanetary disc. We argue instead that terrestrial planets and super-Earths have two clearly distinct formation pathways that are regulated by the pebble reservoir of the disc. Through numerical integrations, which combine pebble accretion and N-body gravity between embryos, we show that a difference of a factor of two in the pebble mass flux is enough to change the evolution from the terrestrial to the super-Earth growth mode. If the pebble mass flux is small, then the initial embryos within the ice line grow slowly and do not migrate substantially, resulting in a widely spaced population of approximately Mars-mass embryos when the gas disc dissipates. Subsequently, without gas being present, the embryos become unstable due to mutual gravitational interactions and a small number of terrestrial planets are formed by mutual collisions. The final terrestrial planets are at most five Earth masses. Instead, if the pebble mass flux is high, then the initial embryos within the ice line rapidly become sufficiently massive to migrate through the gas disc. Embryos concentrate at the inner edge of the disc and growth accelerates through mutual merging. This leads to the formation of a system of closely spaced super-Earths in the five to twenty Earth-mass range, bounded by the pebble isolation mass. Generally, instabilities of these super-Earth systems after the disappearance of the gas disc trigger additional merging events and dislodge the system from resonant chains. Therefore, the key difference between the two growth modes is whether embryos grow fast enough to undergo significant migration. The terrestrial growth mode produces small rocky planets on wider orbits like those in the solar system whereas the super-Earth growth mode produces planets in short-period orbits inside 1 AU, with masses larger than the Earth that should be surrounded by a primordial H/He atmosphere, unless subsequently lost by stellar irradiation. The pebble flux – which controls the transition between the two growth modes – may be regulated by the initial reservoir of solids in the disc or the presence of more distant giant planets that can halt the radial flow of pebbles.
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Tikoo, Sonia M., und Linda T. Elkins-Tanton. „The fate of water within Earth and super-Earths and implications for plate tectonics“. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 375, Nr. 2094 (17.04.2017): 20150394. http://dx.doi.org/10.1098/rsta.2015.0394.
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The Earth is likely to have acquired most of its water during accretion. Internal heat of planetesimals by short-lived radioisotopes would have caused some water loss, but impacts into planetesimals were insufficiently energetic to produce further drying. Water is thought to be critical for the development of plate tectonics, because it lowers viscosities in the asthenosphere, enabling subduction. The following issue persists: if water is necessary for plate tectonics, but subduction itself hydrates the upper mantle, how is the upper mantle initially hydrated? The giant impacts of late accretion created magma lakes and oceans, which degassed during solidification to produce a heavy atmosphere. However, some water would have remained in the mantle, trapped within crystallographic defects in nominally anhydrous minerals. In this paper, we present models demonstrating that processes associated with magma ocean solidification and overturn may segregate sufficient quantities of water within the upper mantle to induce partial melting and produce a damp asthenosphere, thereby facilitating plate tectonics and, in turn, the habitability of Earth-like extrasolar planets. This article is part of the themed issue ‘The origin, history and role of water in the evolution of the inner Solar System’.
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Wakeford, H. R., und P. A. Dalba. „The exoplanet perspective on future ice giant exploration“. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 378, Nr. 2187 (09.11.2020): 20200054. http://dx.doi.org/10.1098/rsta.2020.0054.
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Exoplanets number in their thousands, and the number is ever increasing with the advent of new surveys and improved instrumentation. One of the most surprising things we have learnt from these discoveries is not that small-rocky planets in their stars habitable zones are likely to be common, but that the most typical size of exoplanets is that not seen in our solar system—radii between that of Neptune and the Earth dubbed mini-Neptunes and super-Earths. In fact, a transiting exoplanet is four times as likely to be in this size regime than that of any giant planet in our solar system. Investigations into the atmospheres of giant hydrogen/helium dominated exoplanets has pushed down to Neptune and mini-Neptune-sized worlds revealing molecular absorption from water, scattering and opacity from clouds, and measurements of atmospheric abundances. However, unlike measurements of Jupiter, or even Saturn sized worlds, the smaller giants lack a ground truth on what to expect or interpret from their measurements. How did these sized worlds form and evolve and was it different from their larger counterparts? What is their internal composition and how does that impact their atmosphere? What informs the energy budget of these distant worlds? In this we discuss what characteristics we can measure for exoplanets, and why a mission to the ice giants in our solar system is the logical next step for understanding exoplanets. This article is part of a discussion meeting issue ‘Future exploration of ice giant systems’.
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Nakayama, Akifumi, Masahiro Ikoma und Naoki Terada. „Survival of Terrestrial N2–O2 Atmospheres in Violent XUV Environments through Efficient Atomic Line Radiative Cooling“. Astrophysical Journal 937, Nr. 2 (29.09.2022): 72. http://dx.doi.org/10.3847/1538-4357/ac86ca.
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Abstract Atmospheres play a crucial role in planetary habitability. Around M dwarfs and young Sun-like stars, planets receiving the same insolation as the present-day Earth are exposed to intense stellar X-rays and extreme-ultraviolet (XUV) radiation. This study explores the fundamental question of whether the atmosphere of present-day Earth could survive in such harsh XUV environments. Previous theoretical studies suggest that stellar XUV irradiation is sufficiently intense to remove such atmospheres completely on short timescales. In this study, we develop a new upper-atmospheric model and re-examine the thermal and hydrodynamic responses of the thermospheric structure of an Earth-like N2–O2 atmosphere, on an Earth-mass planet, to an increase in the XUV irradiation. Our model includes the effects of radiative cooling via electronic transitions of atoms and ions, known as atomic line cooling, in addition to the processes accounted for by previous models. We demonstrate that atomic line cooling dominates over the hydrodynamic effect at XUV irradiation levels greater than several times the present level of the Earth. Consequentially, the atmosphere’s structure is kept almost hydrostatic, and its escape remains sluggish even at XUV irradiation levels up to a thousand times that of the Earth at present. Our estimates for the Jeans escape rates of N2–O2 atmospheres suggest that these 1 bar atmospheres survive in early active phases of Sun-like stars. Even around active late M dwarfs, N2–O2 atmospheres could escape significant thermal loss on timescales of gigayears. These results give new insights into the habitability of terrestrial exoplanets and the Earth’s climate history.
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Mishra, R. K., und S. C. Dubey. „Solar Activity Cause and Effect of Climate Variability and Their Various Impacts“. British Journal of Multidisciplinary and Advanced Studies 4, Nr. 2 (17.03.2023): 21–38. http://dx.doi.org/10.37745/bjmas.2022.0133.
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This paper addresses the Solar Activity cause and effect of climate change and their various impacts. Earth’s climate is determined by complex interactions among the Sun, oceans, atmosphere, cryosphere, land surface and biosphere. The Sun is the principal driving force for Earth’s weather and climate. The Sun’s energy is distributed unevenly on Earth’s surface due to the tilt of Earth’s axis of rotation. Over the course of a year, the angle of rotation results in equatorial areas receiving more solar energy than those near the poles. As a result, the tropical oceans and land masses absorb a great deal more heat than the other regions of Earth. The atmosphere and oceans act together to redistribute this heat. As the equatorial waters warm air near the ocean surface, it expands, rises and drifts towards the poles; cooler denser air from the subtropics and the poles moves toward the equator to take its place. This continual redistribution of heat is modified by the planet’s west to east rotation and the Coriolis force associated with the planet’s spherical shape, giving rise to the high jet streams and the prevailing westerly trade winds. The winds, in turn, along with Earth’s rotation, drive large ocean currents such as the Gulf Stream in the North Atlantic, the Humboldt Current in the South Pacific, and the North and South Equatorial Currents. Ocean currents redistribute warmers waters away from the tropics towards the poles. The ocean and atmosphere exchange heat and water, carbon dioxide and other gases. By its mass and high heat capacity, the ocean moderates climate change from season to season and year to year. These complex, changing atmospheric and oceanic patterns help determine Earth’s weather and climate. Scientists all over the world are making predictions about the ill effects of Global warming and connecting events. The effect of global warming is increasing the average temperature of the Earth. A rise in Earth’s temperatures can in turn root to other alterations in the ecology, including an increasing sea level and modifying the quantity and pattern of rainfall. These modifications may boost the occurrence and concentration of severe climate events, such as floods, famines, heat waves, tornados, and twisters. Other consequences may comprise of higher or lower agricultural outputs, glacier melting, lesser summer stream flows, genus extinctions and rise in the ranges of disease vectors. As an effect of global warming species like golden toad, harlequin frog of Costa Rica has already become extinct. There are number of species that have a threat of disappearing soon as an effect of global warming. As an effect of global warming various new diseases have emerged lately. These diseases are occurring frequently due to the increase in Earths average temperature since the bacteria can survive better in elevated temperatures and even multiply faster when the conditions are favorable. The global warming is extending the distribution of mosquitoes due to the increase in humidity levels and their frequent growth in warmer atmosphere. Various diseases due to ebola, hanta and machupo virus are expected due to warmer climates. The marine life is also very sensitive to the increase in temperatures. The effect of global warming will definitely be seen on some species in the water. A survey was made in which the marine life reacted significantly to the changes in water temperatures. It is expected that many species will die off or become extinct due to the increase in the temperatures of the water, whereas various other species, which prefer warmer waters, will increase tremendously. Perhaps the most disturbing changes are expected in the coral reefs that are expected to die off as an effect of global warming. The global warming is expected to cause irreversible changes in the ecosystem and the behavior of animals
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Chen, Howard, und Seth A. Jacobson. „Impact induced atmosphere-mantle exchange sets the volatile elemental ratios on primitive Earths“. Earth and Planetary Science Letters 594 (September 2022): 117741. http://dx.doi.org/10.1016/j.epsl.2022.117741.
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Chilingar, G. V., O. G. Sorokhtin, L. F. Khilyuk, M. Haroun und A. Albannay. „Absorption of the Solar Ultraviolet Radiation by the Earths Atmosphere and Ozone Formation“. Journal of Sustainable Energy Engineering 1, Nr. 2 (01.04.2013): 161–68. http://dx.doi.org/10.7569/jsee.2012.629509.
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Cridland, Alexander J., Christian Eistrup und Ewine F. van Dishoeck. „Connecting planet formation and astrochemistry“. Astronomy & Astrophysics 627 (Juli 2019): A127. http://dx.doi.org/10.1051/0004-6361/201834378.
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Combining a time-dependent astrochemical model with a model of planet formation and migration, we compute the carbon-to-oxygen ratio (C/O) of a range of planetary embryos starting their formation in the inner solar system (1–3 AU). Most of the embryos result in hot Jupiters (M ≥ MJ, orbital radius <0.1 AU) while the others result in super-Earths at wider orbital radii. The volatile and ice abundance of relevant carbon and oxygen bearing molecular species are determined through a complex chemical kinetic code that includes both gas and grain surface chemistry. This is combined with a model for the abundance of the refractory dust grains to compute the total carbon and oxygen abundance in the protoplanetary disk available for incorporation into a planetary atmosphere. We include the effects of the refractory carbon depletion that has been observed in our solar system, and posit two models that would put this missing carbon back into the gas phase. This excess gaseous carbon then becomes important in determining the final planetary C/O because the gas disk now becomes more carbon rich relative to oxygen (high gaseous C/O). One model, where the carbon excess is maintained throughout the lifetime of the disk results in hot Jupiters that have super-stellar C/O. The other model deposits the excess carbon early in the disk life and allows it to advect with the bulk gas. In this model the excess carbon disappears into the host star within 0.8 Myr, returning the gas disk to its original (substellar) C/O, so the hot Jupiters all exclusively have substellar C/O. This shows that while the solids tend to be oxygen rich, hot Jupiters can have super-stellar C/O if a carbon excess can be maintained by some chemical processing of the dust grains. The atmospheric C/O of the super-Earths at larger radii are determined by the chemical interactions between the gas and ice phases of volatile species rather than the refractory carbon model. Whether the carbon and oxygen content of the atmosphere was accreted primarily by gas or solid accretion is heavily dependent on the mass of the atmosphere and where in the disk the growing planet accreted.
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Hintz, Dominik, Sarah Peacock, Travis Barman, Birgit Fuhrmeister, Evangelos Nagel, Andreas Schweitzer, Sandra V. Jeffers et al. „Modeling the Chromosphere and Transition Region of Planet-hosting Star GJ 436“. Astrophysical Journal 954, Nr. 1 (23.08.2023): 73. http://dx.doi.org/10.3847/1538-4357/ace103.
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Abstract Ahead of upcoming space missions intending to conduct observations of low-mass stars in the ultraviolet (UV) spectral region it becomes imperative to simultaneously conduct atmospheric modeling from the UV to the visible (VIS) and near-infrared (NIR). Investigations on extended spectral regions will help to improve the overall understanding of the diversity of spectral lines arising from very different atmospheric temperature regions. Here we investigate atmosphere models with a chromosphere and transition region for the M2.5V star GJ 436, which hosts a close-in Hot Neptune. The atmosphere models are guided by observed spectral features from the UV to the VIS/NIR originating in the chromosphere and transition region of GJ 436. High-resolution observations from the Hubble Space Telescope and Calar Alto high-Resolution search for M dwarfs with Exo-earths with Near-infrared and optical Echelle Spectrographs (CARMENES) are used to obtain an appropriate model spectrum for the investigated M dwarf. We use a large set of atomic species considered in nonlocal thermodynamic equilibrium conditions within our PHOENIX model computations to approximate the physics within the low-density atmospheric regions. In order to obtain an overall match for the nonsimultaneous observations, it is necessary to apply a linear combination of two model spectra, where one of them better reproduces the UV lines while the other better represents the lines from the VIS/NIR range. This is needed to adequately handle different activity states across the observations.
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КУЗЬМИН, Ю. Д., und В. Г. САХНО. „Water origin and its role in the Earth’s evolution“. Вестник ДВО РАН, Nr. 210(2) (27.04.2020): 115–29. http://dx.doi.org/10.37102/08697698.2020.210.2.015.
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По одной из гипотез, вода на Земле имеет метеорное (поверхностное), а не ювенильное (земное) происхождение. Она не может образовываться в конденсированных средах, т.е. в недрах планеты, как считали и считают многие геологи и геофизики. Данный вывод требует других подходов, отличных от устоявшихся взглядов на происхождение воды, эволюцию гидросферы, атмосферы и содержания воды в горных породах на разных геофизических уровнях Земли и других планетах Солнечной системы. Согласно нашей гипотезе, вода на Земле образовалась в результате синтеза водорода и кислорода из космического газопылевого вещества на горячей поверхности твердой планеты с последующим формированием атмосферы, гидросферы Земли и их активным участием в эволюции Земли, во всех геофизических и геохимических процессах. There is one hypothesis that the Earths water is of meteoric rather than endogenous origin. It cannot emerge in condensed environments, namely in the planets interior, as it was believed by many geologists and geophysics. This inference requires other approaches differing from the fixed views on the water origin, evolvement of hydrosphere and atmosphere, water content of rocks in various geophysical layers of the Earth and on other planets of the Solar System. According to our hypothesis, water is a result of synthesis of hydrogen and oxygen from interstellar medium on a hot surface of terrestrial planet followed by the birth of atmosphere and hydrosphere which played a great part in the evolution and all geophysical and geochemical processes of the Earth.
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Finchenko, V. S., und A. A. Ivankov. „Numerical study of thermal destruction of the "Chelyabinsk" meteorite when entering the Earths atmosphere“. Computer Research and Modeling 5, Nr. 6 (Dezember 2013): 941–56. http://dx.doi.org/10.20537/2076-7633-2013-5-6-941-956.
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Maillard, Julien, Nathalie Carrasco, Christopher P. Rüger, Audrey Chatain, Isabelle Schmitz-Afonso, Chad R. Weisbrod, Laetitia Bailly et al. „Humid Evolution of Haze in the Atmosphere of Super-Earths in the Habitable Zone“. Astrobiology 23, Nr. 6 (01.06.2023): 723–32. http://dx.doi.org/10.1089/ast.2022.0021.
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Yan, F., R. A. E. Fosbury, M. G. Petr-Gotzens, G. Zhao, W. Wang, L. Wang, Y. Liu und E. Pallé. „High-resolution transmission spectrum of the Earth's atmosphere-seeing Earth as an exoplanet using a lunar eclipse“. International Journal of Astrobiology 14, Nr. 2 (12.09.2014): 255–66. http://dx.doi.org/10.1017/s1473550414000172.
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AbstractWith the rapid developments in the exoplanet field, more and more terrestrial exoplanets are being detected. Characterizing their atmospheres using transit observations will become a key datum in the quest for detecting an Earth-like exoplanet. The atmospheric transmission spectrum of our Earth will be an ideal template for comparison with future exo-Earth candidates. By observing a lunar eclipse, which offers a similar configuration to that of an exoplanet transit, we have obtained a high-resolution and high signal-to-noise ratio (SNR) transmission spectrum of the Earth's atmosphere. This observation was performed with the High Resolution Spectrograph at Xinglong Station, China during the total lunar eclipse in December 2011. We compare the observed transmission spectrum with our atmospheric model, and determine the characteristics of the various atmospheric species in detail. In the transmission spectrum, O2, O3, O2 · O2, NO2 and H2O are detected, and their column densities are measured and compared with the satellites data. The visible Chappuis band of ozone produces the most prominent absorption feature, which suggests that ozone is a promising molecule for the future exo-Earth characterization. Due to the high resolution and high SNR of our spectrum, several novel details of the Earth atmosphere's transmission spectrum are presented. The individual O2 lines are resolved and O2 isotopes are clearly detected. Our new observations do not confirm the absorption features of Ca II or Na I which have been reported in previous lunar eclipse observations. However, features in these and some other strong Fraunhofer line positions do occur in the observed spectrum. We propose that these are due to a Raman-scattered component in the forward-scattered sunlight appearing in the lunar umbral spectrum. Water vapour absorption is found to be rather weak in our spectrum because the atmosphere we probed is relatively dry, which prompts us to discuss the detectability of water vapour in Earth-like exoplanet atmospheres.
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Essack, Zahra, Avi Shporer, Jennifer A. Burt, Sara Seager, Saverio Cambioni, Zifan Lin, Karen A. Collins et al. „TOI-1075 b: A Dense, Massive, Ultra-short-period Hot Super-Earth Straddling the Radius Gap“. Astronomical Journal 165, Nr. 2 (10.01.2023): 47. http://dx.doi.org/10.3847/1538-3881/ac9c5b.
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Abstract Populating the exoplanet mass–radius diagram in order to identify the underlying relationship that governs planet composition is driving an interdisciplinary effort within the exoplanet community. The discovery of hot super-Earths—a high-temperature, short-period subset of the super-Earth planet population—has presented many unresolved questions concerning the formation, evolution, and composition of rocky planets. We report the discovery of a transiting, ultra-short-period hot super-Earth orbiting TOI-1075 (TIC351601843), a nearby (d = 61.4 pc) late-K/early-M-dwarf star, using data from the Transiting Exoplanet Survey Satellite. The newly discovered planet has a radius of 1.791 − 0.081 + 0.116 R ⊕ and an orbital period of 0.605 day (14.5 hr). We precisely measure the planet mass to be 9.95 − 1.30 + 1.36 M ⊕ using radial velocity measurements obtained with the Planet Finder Spectrograph mounted on the Magellan II telescope. Our radial velocity data also show a long-term trend, suggesting an additional planet in the system. While TOI-1075 b is expected to have a substantial H/He atmosphere given its size relative to the radius gap, its high density ( 9.32 − 1.85 + 2.05 g cm−3) is likely inconsistent with this possibility. We explore TOI-1075 b’s location relative to the M-dwarf radius valley, evaluate the planet’s prospects for atmospheric characterization, and discuss potential planet formation mechanisms. Studying the TOI-1075 system in the broader context of ultra-short-period planetary systems is necessary for testing planet formation and evolution theories and density-enhancing mechanisms and for future atmospheric and surface characterization studies via emission spectroscopy with the JWST.
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Rogers, James G., und James E. Owen. „Unveiling the planet population at birth“. Monthly Notices of the Royal Astronomical Society 503, Nr. 1 (24.02.2021): 1526–42. http://dx.doi.org/10.1093/mnras/stab529.
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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.
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Godolt, Mareike, Nicola Tosi, Barbara Stracke, John Lee Grenfell, Thomas Ruedas, Tilman Spohn und Heike Rauer. „The habitability of stagnant-lid Earths around dwarf stars“. Astronomy & Astrophysics 625 (30.04.2019): A12. http://dx.doi.org/10.1051/0004-6361/201834658.
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Context. The habitability of a planet depends on various factors, such as the delivery of water during its formation, the co-evolution of the interior and the atmosphere, and the stellar irradiation which changes in time. Aims. Since an unknown number of rocky extrasolar planets may operate in a one-plate convective regime, i.e. without plate tectonics, our aim is to understand the conditions under which planets in such a stagnant-lid regime may support habitable surface conditions. Understanding the interaction of the planetary interior and outgassing of volatiles in combination with the evolution of the host star is crucial to determining the potential habitability. M-dwarf stars in particular possess a high-luminosity pre-main sequence phase that endangers the habitability of planets around them via water loss. We therefore explore the potential of secondary outgassing from the planetary interior to rebuild a water reservoir allowing for habitability at a later stage. Methods. We compute the boundaries of the habitable zone around M-, K-, G-, and F-dwarf stars using a 1D cloud-free radiative-convective climate model accounting for the outgassing history of CO2 and H2O from an interior evolution and outgassing model for different interior compositions and stellar luminosity evolutions. Results. The outer edge of the habitable zone strongly depends on the amount of CO2 outgassed from the interior, while the inner edge is mainly determined via the stellar irradiation, as soon as a sufficiently large water reservoir has been outgassed. A build-up of a secondary surface and atmospheric water reservoir for planets around M-dwarf stars is possible even after severe water loss during the high-luminosity pre-main sequence phase as long as some water has been retained within the mantle. For small mantle water reservoirs, between 62 and 125 ppm, a time delay in outgassing from the interior permits such a secondary water reservoir build-up especially for early and mid-M dwarfs because their pre-main sequence lifetimes are shorter than the outgassing timescale. Conclusions. We show that Earth-like stagnant-lid planets allow for habitable surface conditions within a continuous habitable zone that is dependent on interior composition. Secondary outgassing from the interior may allow for habitability of planets around M-dwarf stars after severe water loss during the high-luminosity pre-main sequence phase by rebuilding a surface water reservoir.
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Johnstone, C. P., M. Güdel, H. Lammer und K. G. Kislyakova. „Upper atmospheres of terrestrial planets: Carbon dioxide cooling and the Earth’s thermospheric evolution“. Astronomy & Astrophysics 617 (September 2018): A107. http://dx.doi.org/10.1051/0004-6361/201832776.
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Context.The thermal and chemical structures of the upper atmospheres of planets crucially influence losses to space and must be understood to constrain the effects of losses on atmospheric evolution.Aims.We develop a 1D first-principles hydrodynamic atmosphere model that calculates atmospheric thermal and chemical structures for arbitrary planetary parameters, chemical compositions, and stellar inputs. We apply the model to study the reaction of the Earth’s upper atmosphere to large changes in the CO2abundance and to changes in the input solar XUV field due to the Sun’s activity evolution from 3 Gyr in the past to 2.5 Gyr in the future.Methods.For the thermal atmosphere structure, we considered heating from the absorption of stellar X-ray, UV, and IR radiation, heating from exothermic chemical reactions, electron heating from collisions with non-thermal photoelectrons, Joule heating, cooling from IR emission by several species, thermal conduction, and energy exchanges between the neutral, ion, and electron gases. For the chemical structure, we considered ~500 chemical reactions, including 56 photoreactions, eddy and molecular diffusion, and advection. In addition, we calculated the atmospheric structure by solving the hydrodynamic equations. To solve the equations in our model, we developed the Kompot code and have provided detailed descriptions of the numerical methods used in the appendices.Results.We verify our model by calculating the structures of the upper atmospheres of the modern Earth and Venus. By varying the CO2abundances at the lower boundary (65 km) of our Earth model, we show that the atmospheric thermal structure is significantly altered. Increasing the CO2abundances leads to massive reduction in thermospheric temperature, contraction of the atmosphere, and reductions in the ion densities indicating that CO2can significantly influence atmospheric erosion. Our models for the evolution of the Earth’s upper atmosphere indicate that the thermospheric structure has not changed significantly in the last 2 Gyr and is unlikely to change signficantly in the next few Gyr. The largest changes that we see take place between 3 and 2 Gyr ago, with even larger changes expected at even earlier times.
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Lapshin, V. B., M. S. Ivanov, N. G. Kotonaeva, V. A. Burov und A. Yu Repin. „Protons of radiation belts as a source of hydrogen in the Earth’s atmosphere“. Доклады Академии наук 489, Nr. 5 (20.12.2019): 502–5. http://dx.doi.org/10.31857/s0869-56524895502-505.
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A scenario is proposed for replenishing the Earths exosphere with atomic hydrogen of cosmic origin. An assessment was made and the coincidence of the total atomic hydrogen content in the exosphere with the number of protons (after thermolization converted into hydrogen ions) precipitated in the SAA zone during the year according to the data of the Meteor M and NOAA‑19 satellites was confirmed. The observed coincidence indicates that the rates of replenishment of hydrogen due to precipitation from radiation belts and dissipation into outer space coincide in order of magnitude. It is concluded that the exosphere hydrogen is mainly of cosmic origin and its main source is the thermalized protons of galactic cosmic rays, solar cosmic rays and partially solar wind.
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Wang, Houqing, Jinliang Wang, Xiang Lei, Xiaochun Wen, Dewei Li, Fupeng Liu, Wenyue Zhou und Shengming Xu. „Separation and Recovery of Rare Earths and Iron from NdFeB Magnet Scraps“. Processes 11, Nr. 10 (30.09.2023): 2895. http://dx.doi.org/10.3390/pr11102895.
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NdFeB magnet scraps contain large amounts of iron, which poses challenges in recycling and greatly hinders the recovery of rare earths through direct hydrometallurgical treatment. To address this issue, we conducted tests using a flash furnace to explore the low-temperature reduction behavior of NdFeB magnet scraps under an H2 atmosphere based on thermodynamic calculations comparing the reduction properties of rare earth oxides (REOs) and iron oxide (FeOx). The results demonstrated that the reduction rate of FeOx surpassed 95% under optimal conditions including a reduction temperature of 723 K, a particle size (D90) of 0.45 μm, and an H2 flow rate of 2 L/min. X-ray diffraction and electron probe microanalysis of the reduction product revealed that the flash reduction at 723 K facilitated the selective reduction of FeOx, owing to efficient mass and heat transfer. Consequently, a two-step magnetic separation process was employed to separate metallic Fe and REOs from the reduction product. Fe-rich phase, obtained with a remarkable Fe distribution ratio of 90.2%, can serve as an economical raw material for weathering steel. Additionally, the REOs are enriched in REO-rich phase, achieving a distribution ratio of 93.9% and significantly boosting the REO concentration from 30.2 to 82.8 wt%.