arXiv subjects

Thomas J. Fauchez

Publications and source records attributed to Thomas J. Fauchez.

At least 37 records · Page 2Linked to original sources

arXiv2024

The CUISINES Framework for Conducting Exoplanet Model Intercomparison Projects, Version 1.0

As JWST begins to return observations, it is more important than ever that exoplanet climate models can consistently and correctly predict the observability of exoplanets, retrieval of their data, and interpretation of planetary environments from that data. Model intercomparisons play a crucial role in this context, especially now when few data are available to validate model predictions. The CUISINES Working Group of NASA's Nexus for Exoplanet System Science (NExSS) supports a systematic approach to evaluating the performance of exoplanet models, and provides here a framework for conducting community-organized exoplanet Model Intercomparison Projects (exoMIPs). The CUISINES framework adapts Earth climate community practices specifically for the needs of exoplanet researchers, encompassing a range of model types, planetary targets, and parameter space studies. It is intended to help researchers to work collectively, equitably, and openly toward common goals. The CUISINES framework rests on five principles: 1) Define in advance what research question(s) the exoMIP is intended to address. 2) Create an experimental design that maximizes community participation, and advertise it widely. 3) Plan a project timeline that allows all exoMIP members to participate fully. 4) Generate data products from model output for direct comparison to observations. 5) Create a data management plan that is workable in the present and scalable for the future. Within the first years of its existence, CUISINES is already providing logistical support to 10 exoMIPs, and will continue to host annual workshops for further community feedback and presentation of new exoMIP ideas.

astro-ph.EP↗

arXiv2024

Interpolation and synthesis of sparse samples in exoplanet atmospheric modeling

This paper highlights methods from geostatistics that are relevant to the interpretation, intercomparison, and synthesis of atmospheric model data, with a specific application to exoplanet atmospheric modeling. Climate models are increasingly used to study theoretical and observational properties of exoplanets, which include a hierarchy of models ranging from fast and idealized models to those that are slower but more comprehensive. Exploring large parameter spaces with computationally-expensive models can be accomplished with sparse sampling techniques, but analyzing such sparse samples can pose challenges for conventional interpolation functions. Ordinary kriging is a statistical method for describing the spatial distribution of a data set in terms of the variogram function, which can be used to interpolate sparse samples across any number of dimensions. Variograms themselves may also be useful diagnostic tools for describing the spatial distribution of model data in exoplanet atmospheric model intercomparison projects. Universal kriging is another method that can synthesize data calculated by models of different complexity, which can be used to combine sparse samples of data from slow models with larger samples of data from fast models. Ordinary and universal kriging can also provide a way to synthesize model predictions with sparse samples of exoplanet observations and may have other applications in exoplanet science.

astro-ph.EP↗

arXiv2024

Modeling Atmospheric Lines By the Exoplanet Community (MALBEC) version 1.0: A CUISINES radiative transfer intercomparison project

Radiative transfer (RT) models are critical in the interpretation of exoplanetary spectra, in simulating exoplanet climates and when designing the specifications of future flagship observatories. However, most models differ in methodologies and input data, which can lead to significantly different spectra. In this paper, we present the experimental protocol of the MALBEC (Modeling Atmospheric Lines By the Exoplanet Community) project. MALBEC is an exoplanet model intercomparison project (exoMIP) that belongs to the CUISINES (Climates Using Interactive Suites of Intercomparisons Nested for Exoplanet Studies) framework which aims to provide the exoplanet community with a large and diverse set of comparison and validation of models. The proposed protocol tests include a large set of initial participating RT models, a broad range of atmospheres (from Hot Jupiters to temperate terrestrials) and several observation geometries, which would allow us to quantify and compare the differences between different RT models used by the exoplanetary community. Two types of tests are proposed: transit spectroscopy and direct imaging modeling, with results from the proposed tests to be published in dedicated follow-up papers. To encourage the community to join this comparison effort and as an example, we present simulation results for one specific transit case (GJ-1214 b), in which we find notable differences in how the various codes handle the discretization of the atmospheres (e.g., sub-layering), the treatment of molecular opacities (e.g., correlated-k, line-by-line) and the default spectroscopic repositories generally used by each model (e.g., HITRAN, HITEMP, ExoMol).

astro-ph.EP↗

arXiv2023

New Mass and Radius Constraints on the LHS 1140 Planets -- LHS 1140 b is Either a Temperate Mini-Neptune or a Water World

The two-planet transiting system LHS 1140 has been extensively observed since its discovery in 2017, notably with $Spitzer$, HST, TESS, and ESPRESSO, placing strong constraints on the parameters of the M4.5 host star and its small temperate exoplanets, LHS 1140 b and c. Here, we reanalyse the ESPRESSO observations of LHS 1140 with the novel line-by-line framework designed to fully exploit the radial velocity content of a stellar spectrum while being resilient to outlier measurements. The improved radial velocities, combined with updated stellar parameters, consolidate our knowledge on the mass of LHS 1140 b (5.60$\pm$0.19 M$_{\oplus}$) and LHS 1140 c (1.91$\pm$0.06 M$_{\oplus}$) with unprecedented precision of 3%. Transits from $Spitzer$, HST, and TESS are jointly analysed for the first time, allowing us to refine the planetary radii of b (1.730$\pm$0.025 R$_{\oplus}$) and c (1.272$\pm$0.026 R$_{\oplus}$). Stellar abundance measurements of refractory elements (Fe, Mg and Si) obtained with NIRPS are used to constrain the internal structure of LHS 1140 b. This planet is unlikely to be a rocky super-Earth as previously reported, but rather a mini-Neptune with a $\sim$0.1% H/He envelope by mass or a water world with a water-mass fraction between 9 and 19% depending on the atmospheric composition and relative abundance of Fe and Mg. While the mini-Neptune case would not be habitable, a water-abundant LHS 1140 b potentially has habitable surface conditions according to 3D global climate models, suggesting liquid water at the substellar point for atmospheres with relatively low CO$_2$ concentration, from Earth-like to a few bars.

astro-ph.EP↗

arXiv2023

3D Global climate model of an exo-Venus: a modern Venus-like atmosphere for the nearby super-Earth LP 890-9 c

The recently discovered super-Earth LP 890-9 c is an intriguing target for atmospheric studies as it transits a nearby, low-activity late-type M-dwarf star at the inner edge of the Habitable Zone. Its position at the runaway greenhouse limit makes it a natural laboratory to study the climate evolution of hot rocky planets. We present the first 3D-GCM exo-Venus model for a modern Venus-like atmosphere (92 bar surface pressure, realistic composition, H$_2$SO$_4$ radiatively-active clouds), applied to the tidally-locked LP 890-9c to inform observations by JWST and future instruments. If LP 890-9 c has developed into a modern exo-Venus, then the modelled temperatures suggest that H$_2$SO$_4$ clouds are possible even in the substellar region. Like on modern Venus, clouds on LP 890-9 c would create a flat spectrum. The strongest CO$_2$ bands in transmission predicted by our model for LP 890-9 c are about 10 ppm, challenging detection, given JWST estimated noise floor. Estimated phase curve amplitudes are 0.9 and 2.4 ppm for continuum and CO$_2$ bands, respectively. While pointing out the challenge to characterise modern exo-Venus analogues, these results provide new insights for JWST proposals and highlight the influence of clouds in the spectrum of hot rocky exoplanet spectra.

astro-ph.EP↗

arXiv2023

The Prospect of Detecting Volcanic Signatures on an ExoEarth Using Direct Imaging

The James Webb Space Telescope (JWST) has provided the first opportunity to study the atmospheres of terrestrial exoplanets and estimate their surface conditions. Earth-sized planets around Sun-like stars are currently inaccessible with JWST however, and will have to be observed using the next generation of telescopes with direct imaging capabilities. Detecting active volcanism on an Earth-like planet would be particularly valuable as it would provide insight into its interior, and provide context for the commonality of the interior states of Earth and Venus. In this work we used a climate model to simulate four exoEarths over eight years with ongoing large igneous province eruptions with outputs ranging from 1.8-60 Gt of sulfur dioxide. The atmospheric data from the simulations were used to model direct imaging observations between 0.2-2.0 $μ$m, producing reflectance spectra for every month of each exoEarth simulation. We calculated the amount of observation time required to detect each of the major absorption features in the spectra, and identified the most prominent effects that volcanism had on the reflectance spectra. These effects include changes in the size of the O$_3$, O$_2$, and H$_2$O absorption features, and changes in the slope of the spectrum. Of these changes, we conclude that the most detectable and least ambiguous evidence of volcanism are changes in both O$_3$ absorption and the slope of the spectrum.

astro-ph.EP↗

arXiv2023

Water Condensation Zones around Main Sequence Stars

Understanding the set of conditions that allow rocky planets to have liquid water on their surface -- in the form of lakes, seas or oceans -- is a major scientific step to determine the fraction of planets potentially suitable for the emergence and development of life as we know it on Earth. This effort is also necessary to define and refine the so-called "Habitable Zone" (HZ) in order to guide the search for exoplanets likely to harbor remotely detectable life forms. Until now, most numerical climate studies on this topic have focused on the conditions necessary to maintain oceans, but not to form them in the first place. Here we use the three-dimensional Generic Planetary Climate Model (PCM), historically known as the LMD Generic Global Climate Model (GCM), to simulate water-dominated planetary atmospheres around different types of Main-Sequence stars. The simulations are designed to reproduce the conditions of early ocean formation on rocky planets due to the condensation of the primordial water reservoir at the end of the magma ocean phase. We show that the incoming stellar radiation (ISR) required to form oceans by condensation is always drastically lower than that required to vaporize oceans. We introduce a Water Condensation Limit, which lies at significantly lower ISR than the inner edge of the HZ calculated with three-dimensional numerical climate simulations. This difference is due to a behavior change of water clouds, from low-altitude dayside convective clouds to high-altitude nightside stratospheric clouds. Finally, we calculated transit spectra, emission spectra and thermal phase curves of TRAPPIST-1b, c and d with H2O-rich atmospheres, and compared them to CO2 atmospheres and bare rock simulations. We show using these observables that JWST has the capability to probe steam atmospheres on low-mass planets, and could possibly test the existence of nightside water clouds.

astro-ph.EP↗

arXiv2023

Functionality of Ice Line Latitudinal EBM Tenacity (FILLET). Protocol Version 1.0. A CUISINES intercomparison project

Energy balance models (EBMs) are one- or two-dimensional climate models that can provide insight into planetary atmospheres, particularly with regard to habitability. Because EBMs are far less computationally intensive than three-dimensional general circulation models (GCMs), they can be run over large, uncertain parameter spaces and can be used to explore long-period phenomena like carbon and Milankovitch cycles. Because horizontal dimensions are incorporated in EBMs, they can explore processes that are beyond the reach of one-dimensional radiative-convective models (RCMs). EBMs are, however, dependent on parameterizations and tunings to account for physical processes that are neglected. Thus, EBMs rely on observations and results from GCMs and RCMs. Different EBMs have included a wide range of parameterizations (for albedo, radiation, and heat diffusion) and additional physics, such as carbon cycling and ice sheets. This CUISINES exoplanet model intercomparison project (exoMIP) will compare various EBMs across a set of numerical experiments. The set of experiments will include Earth-like planets at different obliquities, parameter sweeps across obliquity, and variations in instellation and CO$_2$ abundance to produce hysteresis diagrams. We expect a range of different results due to the choices made in the various codes, highlighting which results are robust across models and which are dependent on parameterizations or other modeling choices. Additionally, it will allow developers to identify model defects and determine which parameterizations are most useful or relevant to the problem of interest. Ultimately, this exoMIP will allow us to improve the consistency between EBMs and accelerate the process of discovering habitable exoplanets.

astro-ph.EP↗

arXiv2022

GCM Constraints on the Detectability of the CO$_2$-CH$_4$ Biosignature Pair on TRAPPIST-1e with JWST

Terrestrial exoplanets such as TRAPPIST-1e will be observed in a new capacity with JWST/NIRSpec, which is expected to be able to detect CO$_2$, CH$_4$, and O$_2$ signals, if present, with multiple co-added transit observations. The CO$_2$-CH$_4$ pair in particular is theorized to be a potential biosignature when inferred to be in chemical disequilibrium. Here, we simulate TRAPPIST-1e's atmosphere using the ExoCAM General Circulation Model (GCM), assuming an optimistic haze-free, tidally locked planet with an aquaplanet surface, with varying atmospheric compositions from $10^{-4}$ bar to 1 bar of partial CO$_2$ pressure with 1 bar of background N$_2$. We investigate cases both with and without a modern Earth-like CH$_4$ mixing ratio to examine the effect of CO$_2$ and CH$_4$ on the transmission spectrum and climate state of the planet. We demonstrate that in the optimistic haze-free cloudy case, H$_2$O, CO$_2$, and CH$_4$ could all be detectable in less than 50 transits within an atmosphere of 1 bar N$_2$ and 10 mbar CO$_2$ during JWST's lifespan with NIRSpec as long as the noise floor is $\lesssim$ 10 ppm. We find that in these optimistic cases, JWST may be able to detect potential biosignature pairs such as CO$_2$-CH$_4$ in TRAPPIST-1e's atmosphere across a variety of atmospheric CO$_2$ content, and that temporal climate variability does not significantly affect spectral feature variability for NIRSpec PRISM.

astro-ph.EP↗

arXiv2022

Community Report from the Biosignatures Standards of Evidence Workshop

The search for life beyond the Earth is the overarching goal of the NASA Astrobiology Program, and it underpins the science of missions that explore the environments of Solar System planets and exoplanets. However, the detection of extraterrestrial life, in our Solar System and beyond, is sufficiently challenging that it is likely that multiple measurements and approaches, spanning disciplines and missions, will be needed to make a convincing claim. Life detection will therefore not be an instantaneous process, and it is unlikely to be unambiguous-yet it is a high-stakes scientific achievement that will garner an enormous amount of public interest. Current and upcoming research efforts and missions aimed at detecting past and extant life could be supported by a consensus framework to plan for, assess and discuss life detection claims (c.f. Green et al., 2021). Such a framework could help increase the robustness of biosignature detection and interpretation, and improve communication with the scientific community and the public. In response to this need, and the call to the community to develop a confidence scale for standards of evidence for biosignature detection (Green et al., 2021), a community-organized workshop was held on July 19-22, 2021. The meeting was designed in a fully virtual (flipped) format. Preparatory materials including readings, instructional videos and activities were made available prior to the workshop, allowing the workshop schedule to be fully dedicated to active community discussion and prompted writing sessions. To maximize global interaction, the discussion components of the workshop were held during business hours in three different time zones, Asia/Pacific, European and US, with daily information hand-off between group organizers.

astro-ph.IM↗

arXiv2022

CAMEMBERT: A Mini-Neptunes GCM Intercomparison, Protocol Version 1.0. A CUISINES Model Intercomparison Project

With an increased focus on the observing and modelling of mini-Neptunes, there comes a need to better understand the tools we use to model their atmospheres. In this paper, we present the protocol for the CAMEMBERT (Comparing Atmospheric Models of Extrasolar Mini-neptunes Building and Envisioning Retrievals and Transits) project, an intercomparison of general circulation models (GCMs) used by the exoplanetary science community to simulate the atmospheres of mini-Neptunes. We focus on two targets well studied both observationally and theoretically with planned JWST Cycle 1 observations: the warm GJ~1214b and the cooler K2-18b. For each target, we consider a temperature-forced case, a clear sky dual-grey radiative transfer case, and a clear sky multi band radiative transfer case, covering a range of complexities and configurations where we know differences exist between GCMs in the literature. This paper presents all the details necessary to participate in the intercomparison, with the intention of presenting the results in future papers. Currently, there are eight GCMs participating (ExoCAM, Exo-FMS, FMS PCM, Generic PCM, MITgcm, RM-GCM, THOR, and the UM), and membership in the project remains open. Those interested in participating are invited to contact the authors.

astro-ph.EP↗

arXiv2022

A transmission spectrum of the sub-Earth planet L98-59~b in 1.1-1.7 $μ$m

With the increasing number of planets discovered by TESS, the atmospheric characterization of small exoplanets is accelerating. L98-59 is a M-dwarf hosting a multi-planet system, and so far, four small planets have been confirmed. The innermost planet b is $\sim15\%$ smaller and $\sim60\%$ lighter than Earth, and should thus have a predominantly rocky composition. The Hubble Space Telescope observed five primary transits of L98-59b in $1.1-1.7\ μ$m, and here we report the data analysis and the resulting transmission spectrum of the planet. We measure the transit depths for each of the five transits and, by combination, we obtain a transmission spectrum with an overall precision of $\sim20$ ppm in for each of the 18 spectrophotometric channels. With this level of precision, the transmission spectrum does not show significant modulation, and is thus consistent with a planet without any atmosphere or a planet having an atmosphere and high-altitude clouds or haze. The scenarios involving an aerosol-free, H$_2$-dominated atmosphere with H$_2$O or CH$_4$ are inconsistent with the data. The transmission spectrum also disfavors, but does not rules out, an H$_2$O-dominated atmosphere without clouds. A spectral retrieval process suggests that an H$_2$-dominated atmosphere with HCN and clouds or haze may be the preferred solution, but this indication is non-conclusive. Future James Webb Space Telescope observations may find out the nature of the planet among the remaining viable scenarios.

astro-ph.EP↗

arXiv2022

Galactic settlement of low-mass stars as a resolution to the Fermi paradox

An expanding civilization could rapidly spread through the galaxy, so the absence of extraterrestrial settlement in the solar system implies that such expansionist civilizations do not exist. This argument, often referred to as the Fermi paradox, typically assumes that expansion would proceed uniformly through the galaxy, but not all stellar types may be equally useful for a long-lived civilization. We suggest that low-mass stars, and K-dwarf stars in particular, would be ideal migration locations for civilizations that originate in a G-dwarf system. We use a modified form of the Drake Equation to show that expansion across all low-mass stars could be accomplished in 2 Gyr, which includes waiting time between expansion waves to allow for a close approach of a suitable destination star. This would require interstellar travel capabilities of no more than ~0.3 ly to settle all M-dwarfs and ~2 ly to settle all K-dwarfs. Even more rapid expansion could occur within 2 Myr, with travel requirements of ~10 ly to settle all M-dwarfs and ~50 ly to settle all K-dwarfs. The search for technosignatures in exoplanetary systems can help to place constraints on the presence of such a "low-mass Galactic Club" in the galaxy today.

physics.pop-ph↗

arXiv2022

Alternative Methylated Biosignatures I: Methyl Bromide, A Capstone Biosignature

The first potential exoplanet biosignature detections are likely to be ambiguous due to the potential for false positives: abiotic planetary processes that produce observables similar to those anticipated from a global biosphere. Here we propose a class of methylated gases as corroborative `capstone' biosignatures. Capstone biosignatures are metabolic products that may be less immediately detectable, but have substantially lower false positive potential, and can thus serve as confirmation for a primary biosignature such as O$_2$. CH$_3$Cl has previously been established as a biosignature candidate, and other halomethane gases such as CH$_3$Br and CH$_3$I have similar potential. These gases absorb in the mid infrared at wavelengths that are likely to be captured while observing primary biosignatures such as O$_3$ or CH$_4$. We quantitatively explore CH$_3$Br as a new capstone biosignature through photochemical and spectral modeling of Earth-like planets orbiting FGKM stellar hosts. We also re-examine the biosignature potential of CH$_3$Cl over the same set of parameters using our updated model. We show that CH$_3$Cl and CH$_3$Br can build up to relatively high levels in M dwarf environments and analyze synthetic spectra of TRAPPIST-1e. Our results suggest that there is a co-additive spectral effect from multiple CH$_3$X gases in an atmosphere, leading to increased signal-to-noise and greater ability to detect a methylated gas feature. These capstone biosignatures are plausibly detectable in exoplanetary atmospheres, have low false positive potential, and would provide strong evidence for life in conjunction with other well established biosignature candidates.

astro-ph.EP↗

arXiv2022

Evaluating the Plausible Range of N2O Biosignatures on Exo-Earths: An Integrated Biogeochemical, Photochemical, and Spectral Modeling Approach

Nitrous oxide (N2O) -- a product of microbial nitrogen metabolism -- is a compelling exoplanet biosignature gas with distinctive spectral features in the near- and mid-infrared, and only minor abiotic sources on Earth. Previous investigations of N2O as a biosignature have examined scenarios using Earthlike N2O mixing ratios or surface fluxes, or those inferred from Earth's geologic record. However, biological fluxes of N2O could be substantially higher, due to a lack of metal catalysts or if the last step of the denitrification metabolism that yields N2 from N2O had never evolved. Here, we use a global biogeochemical model coupled with photochemical and spectral models to systematically quantify the limits of plausible N2O abundances and spectral detectability for Earth analogs orbiting main-sequence (FGKM) stars. We examine N2O buildup over a range of oxygen conditions (1%-100% present atmospheric level) and N2O fluxes (0.01-100 teramole per year; Tmol = 10^12 mole) that are compatible with Earth's history. We find that N2O fluxes of 10 [100] Tmol yr$^{-1}$ would lead to maximum N2O abundances of ~5 [50] ppm for Earth-Sun analogs, 90 [1600] ppm for Earths around late K dwarfs, and 30 [300] ppm for an Earthlike TRAPPIST-1e. We simulate emission and transmission spectra for intermediate and maximum N2O concentrations that are relevant to current and future space-based telescopes. We calculate the detectability of N2O spectral features for high-flux scenarios for TRAPPIST-1e with JWST. We review potential false positives, including chemodenitrification and abiotic production via stellar activity, and identify key spectral and contextual discriminants to confirm or refute the biogenicity of the observed N2O.

astro-ph.EP↗

arXiv2022

Opportunities for Technosignature Science in the Planetary Science and Astrobiology Decadal Survey

Solar system exploration provides numerous possibilities for advancing technosignature science. The search for life in the solar system includes missions designed to search for evidence of biosignatures on other planetary bodies, but many missions could also attempt to search for and constrain the presence of technology within the solar system. Technosignatures and biosignatures represent complementary approaches toward searching for evidence of life in our solar neighborhood, and beyond. This report summarizes the potential technosignature opportunities within ongoing solar system exploration and the recommendations of the "Origins, Worlds, and Life" Planetary Science and Astrobiology Decadal Survey. We discuss opportunities for constraining the prevalence of technosignatures within the solar system using current or future missions at negligible additional cost, and we present a preliminary assessment of gaps that may exist in the search for technosignatures within the solar system.

astro-ph.IM↗

arXiv2022

The Sparse Atmospheric MOdel Sampling Analysis (SAMOSA) intercomparison: Motivations and protocol version 1.0. A CUISINES model intercomparison project

Planets in synchronous rotation around low-mass stars are the most salient targets for current ground- and space-based missions to observe and characterize. Such model calculations can help to prioritize targets for observation with current and future missions; however, intrinsic differences in the complexity and physical parameterizations of various models can lead to different predictions of a planet's climate state. Understanding such model differences is necessary if such models are to guide target selection and aid in the analysis of observations. This paper presents a protocol to intercompare models of a hypothetical planet with a 15 day synchronous rotation period around a 3000 K blackbody star across a parameter space of surface pressure and incident instellation. We conduct a sparse sample of 16 cases from a previously published exploration of this parameter space with the ExoPlaSim model. By selecting particular cases across this broad parameter space, the SAMOSA intercomparison will identify areas where simpler models are sufficient as well as areas where more complex GCMs are required. Our preliminary comparison using ExoCAM shows general consistency between the climate state predicted by ExoCAM and ExoPlaSim except in regions of the parameter space most likely to be in a steam atmosphere or incipient runaway greenhouse state. We use this preliminary analysis to define several options for participation in the intercomparison by models of all levels of complexity. The participation of other GCMs is crucial to understand how the atmospheric states across this parameter space differ with model capabilities.

astro-ph.EP↗

arXiv2022

The TRAPPIST-1 Habitable Atmosphere Intercomparison (THAI). Part I: Dry Cases -- The fellowship of the GCMs

With the commissioning of powerful, new-generation telescopes such as the James Webb Space Telescope (JWST) and the ground-based Extremely Large Telescopes, the first characterization of a high molecular weight atmosphere around a temperate rocky exoplanet is imminent. Atmospheric simulations and synthetic observables of target exoplanets are essential to prepare and interpret these observations. Here we report the results of the first part of the TRAPPIST-1 Habitable Atmosphere Intercomparison (THAI) project, which compares 3D numerical simulations performed with four state-of-the-art global climate models (ExoCAM, LMD-Generic, ROCKE-3D, Unified Model) for the potentially habitable target TRAPPIST-1e. In this first part, we present the results of dry atmospheric simulations. These simulations serve as a benchmark to test how radiative transfer, subgrid-scale mixing (dry turbulence and convection), and large-scale dynamics impact the climate of TRAPPIST-1e and consequently the transit spectroscopy signature as seen by JWST. To first order, the four models give results in good agreement. The intermodel spread in the global mean surface temperature amounts to 7K (6K) for the N2-dominated (CO2-dominated) atmosphere. The radiative fluxes are also remarkably similar (intermodel variations less than 5%), from the surface (1 bar) up to atmospheric pressures around 5 mbar. Moderate differences between the models appear in the atmospheric circulation pattern (winds) and the (stratospheric) thermal structure. These differences arise between the models from (1) large-scale dynamics, because TRAPPIST-1e lies at the tipping point between two different circulation regimes (fast and Rhines rotators) in which the models can be alternatively trapped, and (2) parameterizations used in the upper atmosphere such as numerical damping.

astro-ph.EP↗