The precise characterization of terrestrial atmospheres with the James Webb Space Telescope (JWST) is one of the utmost goals of exoplanet astronomy in the next decade. With JWST's impending launch, it is crucial we are well prepared to understand the subtleties of terrestrial atmospheres - particularly ones we may have not needed to consider before due to instrumentation limitations. In this work we show that patchy ice cloud variability is present in the upper atmospheres of M-dwarf terrestrial planets, particularly along the limbs. Here we test whether these variable clouds will introduce unexpected biases in the multi-epoch observations necessary to constrain atmospheric abundances. Using 3D ExoCAM general circulation models (GCMs) of TRAPPIST-1e, we simulate five different climates with varying pCO$_2$ to explore the strength of this variability. These models are post-processed using NASA Goddard's Planetary Spectrum Generator (PSG) and PandExo to generate simulated observations with JWST's NIRSpec PRISM mode at 365 different temporal outputs from each climate. Assuming the need for 10 transits of TRAPPIST-1e to detect molecular features at great confidence, we then use CHIMERA to retrieve on several randomly selected weighted averages of our simulated observations to explore the effect of multi-epoch observations with variable cloud cover along the limb on retrieved abundances. We find that the variable spectra do not affect retrieved abundances at detectable levels for our sample of TRAPPIST-1e models.
Context. New estimates of the masses and radii of the seven planets orbiting the ultracool M-dwarf TRAPPIST-1 star permit improved modelling of their compositions, heating by tidal dissipation, and removal of tidal heat by solid-state convection. Aims. Here, we compute the heat flux due to insolation and tidal heating for the inner four planets. Methods. We apply a Maxwell viscoelastic rheology to compute the tidal response of the planets using the volume-weighted average of the viscosities and rigidities of the metal, rock, high-pressure ice and liquid water/ice I layers. Results. We show tha…
TRAPPIST-1 planets are invaluable for the study of comparative planetary science outside our Solar System and possibly habitability. First, we derive from N-body simulations possible planetary evolution scenarios, and show that each of the planets are likely to be in synchronous rotation. We then use a 3-D Global Climate Model to explore the possible climates of cool planets of the TRAPPIST-1 system. In particular, we look at the conditions required for cool planets to prevent possible volatile species to be lost by permanent condensation, irreversible burying or photochemical destruction. We …
The seven approximately Earth-sized transiting planets in the \object{TRAPPIST-1} system provide a unique opportunity to explore habitable zone and non-habitable zone small planets within the same system. Its habitable zone exoplanets -- due to their favorable transit depths -- are also worlds for which atmospheric transmission spectroscopy is within reach with the Hubble Space Telescope (HST) and with the James Webb Space Telescope (JWST). We present here an independent reduction and analysis of two \textit{HST} Wide Field Camera 3 (WFC3) near-infrared transit spectroscopy datasets for six pl…
Context. Planetary mass and radius data are showing a wide variety in densities of low-mass exoplanets. This includes sub-Neptunes, whose low densities can be explained with the presence of a volatile-rich layer. Water is one of the most abundant volatiles, which can be in the form of different phases depending on the planetary surface conditions. To constrain their composition and interior structure, it is required to develop models that calculate accurately the properties of water at its different phases. Aims. We present an interior structure model that includes a multiphase water layer wit…
Multiple planet systems provide an ideal laboratory for probing exoplanet composition, formation history and potential habitability. For the TRAPPIST-1 planets, the planetary radii are well established from transits (Gillon et al., 2016, Gillon et al., 2017), with reasonable mass estimates coming from transit timing variations (Gillon et al., 2017, Wang et al., 2017) and dynamical modeling (Quarles et al., 2017). The low bulk densities of the TRAPPIST-1 planets demand significant volatile content. Here we show using mass-radius-composition models, that TRAPPIST-1f and g likely contain substant…
Interior characterization traditionally relies on individual planetary properties, ignoring correlations between different planets of the same system. For multi-planetary systems, planetary data are generally correlated. This is because, the differential masses and radii are better constrained than absolute planetary masses and radii. We explore such correlations and data specific to the multiplanetary-system of TRAPPIST-1 and study their value for our understanding of planet interiors. Furthermore, we demonstrate that the rocky interior of planets in a multi-planetary system can be preferenti…
We present a study on the formation of planetary systems around low mass stars similar to Trappist-1, through the accretion of either planetesimals or pebbles. The aim is to determine if the currently observed systems around low mass stars favour one scenario over the other. We ran numerous N-body simulations, coupled to a thermally evolving viscous disc model, including prescriptions for planet migration and photoevaporation. We examine the differences between the pebble and planetesimal accretion scenarios, but also look at the influences of disc mass, planetesimal size, and the percentage o…
We report the multi-epoch detections of the water ice in 2.8-4.2 micron spectra of two Herbig Ae stars, PDS 144N (A2 IVe) and PDS 453 (F2 Ve), which have an edge-on circumstellar disk. The detected water ice absorption is found to originate from their protoplanetary disks. The spectra show a relatively shallow absorption of water ice around 3.1 micron for both objects. The optical depths of the water ice absorption are ~0.1 and ~0.2 for PDS 144N and PDS 453, respectively. Compared to the water ice previously detected in low-mass young stellar objects with an edge-on disk with a similar inclina…
We obtained linear polarization photometry ($J$-band) and low-resolution spectroscopy ($ZJ$-bands) of Trappist-1, which is a planetary system formed by an M8-type low-mass star and seven temperate, Earth-sized planets. The photopolarimetric monitoring campaign covered 6.5 h of continuous observations including one full transit of planet Trappist-1d and partial transits of Trappist-1b and e. The spectrophotometric data and the photometric light curve obtained over epochs with no planetary transits indicate that the low-mass star has very low level of linear polarization compatible with a null v…
Detecting atmospheres in the presence of stellar contamination: an empirically calibrated framework applied to four JWST/NIRSpec PRISM transits of TRAPPIST-1c
DTU Space, Technical University of Denmark（丹麦技术大学空间研究所）
Tidally locked terrestrial planets around low-mass stars are the prime targets for future atmospheric characterizations of potentially habitable systems, especially the three nearby ones--Proxima b, TRAPPIST-1e, and LHS 1140b. Previous studies suggest that if these planets have surface ocean they would be in an eyeball-like climate state: ice-free in the vicinity of the substellar point and ice-covered in the rest regions. However, an important component of the climate system--sea ice dynamics has not been well studied in previous studies. A fundamental question is: would the open ocean be sta…
JWST Reveals Refractory-Rich Water Ice in Interstellar Comet 3I/ATLAS: Evidence for a Continuum of Grain Properties across Protoplanetary Disks
Southwest Research Institute（西南研究院）；University of Maryland, College Park（马里兰大学帕克分校）；NASA Goddard Space Flight Center（美国宇航局戈达德太空飞行中心）；Catholic University of America（美利坚天主教大学）；Auburn University（奥本大学）；Universität Bern（伯尔尼大学）
Ultraviolet-Driven Atmospheric Degeneracies Challenge Conventional Biosignature Frameworks for Terrestrial Planets with Ultracool M Dwarf Hosts: An Archean-Analog TRAPPIST-1 e Case Study
University of California, Riverside（加州大学河滨分校）；Blue Marble Space Institute of Science（蓝大理石太空科学研究所）；University of Maryland, Baltimore County（马里兰大学巴尔的摩县分校）；NASA Goddard Space Flight Center（NASA戈达德太空飞行中心）；SETI Institute（搜寻地外文明研究所）；NASA Ames Research Center（NASA艾姆斯研究中心）
Mars' polar layered deposits (PLD) are comprised of layers of varying dust-to-water ice volume mixing ratios (VMR) that may record astronomically-forced climatic variation over Mars' recent orbital history. Retracing the formation of these layers by quantifying the sensitivity of deposition rates of polar material to astronomical forcing is critical for the interpretation of this record. Using a Mars global climate model (GCM), we investigate the sensitivity of annual polar water ice and dust surface deposition to various obliquities and surface water ice distributions at zero eccentricity, pr…
We present IRTF/SpeX and NEOWISE observations of the dynamically new comet C/2013 US$_{10}$ (Catalina), hereafter US10, from 5.8 au inbound, to near perihelion at 1.3 au, and back to 5.0 au outbound. We detect water ice in the coma of US10, assess and monitor the physical properties of the ice as insolation varies with heliocentric distance, and investigate the relationship between water ice and CO$_{2}$. This set of measurements is unique in orbital coverage and can be used to infer the physical evolution of the ice and, potentially, the nucleus composition. We report (1) nearly identical nea…
Context: Transmission spectroscopy has proven to be a useful tool for the study of exoplanet atmospheres, and has lead to the detection of a small number of elements and molecules (Na, K, H$_2$O), but also revealed that many planets show flat transmission spectra consistent with the presence of opaque high-altitude hazes or clouds. Aims: We apply this technique to the $M_P=0.38 M_{jup}$, $R_p=1.12 R_{jup}$, $P=2.78d$ planet WASP-49b, aiming to characterize its transmission spectrum between 0.73 and 1 $\mathrmμ$m and search for the features of K and H$_2$O. Methods: Three transits of WASP-49b h…
Context: The dwarf planet (1) Ceres - next target of the NASA Dawn mission - is the largest body in the asteroid main belt; although several observations of this body have been performed so far, the presence of surface water ice is still questioned. Aims: Our goal is to better understand the surface composition of Ceres, and to constrain the presence of exposed water ice. Methods: We acquired new visible and near-infrared spectra at the Telescopio Nazionale Galileo (TNG, La Palma, Spain), and reanalyzed literature spectra in the 3-$μ$m region. Results: We obtained the first rotationally-resolv…
Models of planet formation have shown that giant planets have a large impact on the number, masses and orbits of terrestrial planets that form. In addition, they play an important role in delivering volatiles from material that formed exterior to the snow-line (the region in the disk beyond which water ice can condense) to the inner region of the disk where terrestrial planets can maintain liquid water on their surfaces. We present simulations of the late stages of terrestrial planet formation from a disk of protoplanets around a solar-type star, and we include a massive planet (from 1 Earth m…
By utilizing satellite-based estimations of the distribution of clouds, we have studied the Earth's large-scale cloudiness behavior according to latitude and surface types (ice, water, vegetation and desert). These empirical relationships are used here to reconstruct the possible cloud distribution of historical epochs of the Earth's history such as the Late Cretaceous (90 Ma ago), the Late Triassic (230 Ma ago), the Mississippian (340 Ma ago), and the Late Cambrian (500 Ma ago), when the landmass distributions were different from today's. With this information, we have been able to simulate t…
Combining stellar occultation observations probing Pluto's atmosphere from 1988 to 2013 and models of energy balance between Pluto's surface and atmosphere, we conclude that Pluto's atmosphere does not collapse at any point in its 248-year orbit. The occultation results show an increasing atmospheric pressure with time in the current epoch, a trend present only in models with a high thermal inertia and a permanent N2 ice cap at Pluto's north rotational pole.
Because WISE J085510.83$-$071442.5 (hereafter WISE 0855-0714) is the coldest known brown dwarf ($\sim250$ K) and one of the Sun's closest neighbors (2.2 pc), it offers a unique opportunity for studying a planet-like atmosphere in an unexplored regime of temperature. To detect and characterize inhomogeneities in its atmosphere (e.g., patchy clouds, hot spots), we have performed time-series photometric monitoring of WISE 0855-0714 at 3.6 and 4.5 micron with the Spitzer Space Telescope during two 23~hr periods that were separated by several months. For both bands, we have detected variability wit…
Analysing high resolution digital Mars images using machine learning
Luleå University of Technology（吕勒奥理工大学）；Wigner RCP（维格纳研究中心）；Konkoly Thege Miklos Astronomical Institute（科诺利·泰格·米克洛什天文研究所）；Research Centre for Astronomy and Earth Sciences（天文与地球科学研究中心）；ELTE Institute of Physics（厄特沃什·罗兰大学物理研究所）；CSFK, MTA Centre of Excellence（匈牙利科学院卓越中心CSFK）
The TRAPPIST-1 Habitable Atmosphere Intercomparison (THAI) project was initiated to compare 3D climate models that are commonly used for predicting theoretical climates of habitable zone extrasolar planets. One of the core models studied as part of THAI is ExoCAM, an independently curated exoplanet branch of the National Center for Atmospheric Research (NCAR) Community Earth System Model (CESM) version 1.2.1. ExoCAM has been used for studying atmospheres of terrestrial extrasolar planets around a variety of stars. To accompany the THAI project and provide a primary reference, here we describe …
