Super-Earths and sub-Neptunes have been found simultaneously in multiplanetary systems, suggesting that they are appropriate to study composition and formation within the same environment. We perform a homogeneous interior structure analysis of five multiplanetary systems to explore the compositional trends and its relation with planet formation. For K2-138, we present revised masses and stellar host chemical abundances to improve the constraints on the planetary interior. We conduct a line-by-line differential spectroscopic analysis on the stellar spectra to obtain its chemical abundances and the planetary parameters. We select multiplanetary systems with five or more low-mass planets that have both mass and radius data available. We carry out a homogeneous interior structure analysis on the systems K2-138, TOI-178, Kepler-11, Kepler-102 and Kepler-80 and estimate the volatile mass fraction of their planets assuming a volatile layer constituted of water in steam and supercritical phases. Our interior-atmosphere model takes into account the effects of irradiation on the surface conditions. K2-138 inner planets present an increasing volatile mass fraction with distance from its host star, while the outer planets present an approximately constant water content. This is similar to the trend observed in TRAPPIST-1 in a previous analysis with the same interior-atmosphere model. The Kepler-102 system could potentially present this trend. In all multiplanetary systems, the low volatile mass fraction of the inner planets could be due to atmospheric escape while the higher volatile mass fraction of the outer planets can be the result of accretion of ice-rich material in the vicinity of the ice line with later inward migration. Kepler-102 and Kepler-80 present inner planets with high core mass fractions which could be due to mantle evaporation, impacts or formation in the vicinity of rocklines.
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…
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…
Planets similar to Earth - but slightly more irradiated - are expected to enter into a runaway greenhouse state, where all surface water rapidly evaporates, forming an optically thick H2O-dominated atmosphere. For Earth, this extreme climate transition is thought to occur for a ~6% increase only of the solar luminosity, though the exact limit at which the transition would occur is still a highly debated topic. In general, the runaway greenhouse is believed to be a fundamental process in the evolution of Earth-size, temperate planets. Using 1-D radiative-convective climate calculations accounti…
Mass-radius relationships for water-rich rocky planets are usually calculated assuming most water is present in condensed (either liquid or solid) form. Planet density estimates are then compared to these mass-radius relationships, even when these planets are more irradiated than the runaway greenhouse irradiation limit (around 1.1~times the insolation at Earth for planets orbiting a Sun-like star), for which water has been shown to be unstable in condensed form and would instead form a thick H2O-dominated atmosphere. Here we use the LMD Generic numerical climate model to derive new mass-radiu…
JWST-DECO: The Impact of Accretion on Mid-Infrared Observable Water in Planet-forming Disks
Center for Astrophysics | Harvard & Smithsonian（哈佛-史密森天体物理中心）；New York University Shanghai（纽约大学上海分校）；Texas State University（德克萨斯州立大学）；University of Virginia（弗吉尼亚大学）；Università degli Studi di Milano（米兰大学）；California Institute of Technology（加州理工学院）；University of Michigan（密歇根大学）；Universidad de Santiago de Chile（智利圣地亚哥大学）；Millennium Nucleus on Young Exoplanets and their Moons (YEMS)（年轻系外行星及其卫星千年核）；Center for Interdisciplinary Research in Astrophysics and Space Science (CIRAS), Universidad de Santiago, Chile（智利圣地亚哥大学跨学科天体物理学与空间科学研究中心）
We present the analysis of the atmospheres of 70 gaseous extrasolar planets via transit spectroscopy with Hubble's Wide Field Camera 3 (WFC3). For over half of these, we statistically detect spectral modulation which our retrievals attribute to molecular species. Among these, we use Bayesian Hierarchical Modelling to search for chemical trends with bulk parameters. We use the extracted water abundance to infer the atmospheric metallicity and compare it to the planet's mass. We also run chemical equilibrium retrievals, fitting for the atmospheric metallicity directly. However, although previous…
Detecting Atmospheric CO2 Trends as Population-Level Signatures for Long-Term Stable Water Oceans and Biotic Activity on Temperate Terrestrial Exoplanets
WASP-39b is a hot Saturn-mass exoplanet with a predicted clear atmosphere based on observations in the optical and infrared. Here we complete the transmission spectrum of the atmosphere with observations in the near-infrared (NIR) over three water absorption features with the Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) G102 (0.8-1.1 microns) and G141 (1.1-1.7 microns) spectroscopic grisms. We measure the predicted high amplitude H2O feature centered at 1.4 microns, and the smaller amplitude features at 0.95 and 1.2 microns, with a maximum water absorption amplitude of 2.4 planetary…
The emergent spectra of close-in, giant exoplanets ("hot Jupiters") are expected to be distinct from those of self-luminous objects with similar effective temperatures because hot Jupiters are primarily heated from above by their host stars rather than internally from the release of energy from their formation. Theoretical models predict a continuum of dayside spectra for hot Jupiters as a function of irradiation level, with the coolest planets having absorption features in their spectra, intermediate-temperature planets having emission features due to thermal inversions, and the hottest plane…
Regolith on Mars exchanges water with the atmosphere on a diurnal basis and this process causes significant variation in the abundance of water vapor at the surface. While previous studies of regolith-atmosphere exchange focus on the abundance, recent in-situ experiments and remote sensing observations measure the isotopic composition of the atmospheric water. We are therefore motivated to investigate isotopic water exchange between the atmosphere and the regolith and determine its effect on the deuterium to hydrogen ratio (D/H) of the atmosphere. We model transport of water in the regolith an…
Methanol is a potentially important impurity in subsurface oceans on Titan and Enceladus. We report measurements of the freezing of methanol-water samples at pressures up to 350~MPa using a volumetric cell with sapphire windows. For low concentrations of methanol, the liquidus temperature is typically a few degrees below the corresponding ice freezing point, while at high concentrations it follows the pure methanol trend. In the Ice-III regime, we observe several long-lived metastable states. The results suggest that methanol is a more effective antifreeze than previously estimated, and might …
[Abridged] Far-infrared observations with Herschel revealed a surprisingly low abundance of cold-water reservoirs in protoplanetary discs. On the other hand, a handful of discs show emission of hot water transitions excited at temperatures above a few hundred Kelvin. In particular, the protoplanetary discs around the Herbig Ae stars HD 100546 and HD 163296 show opposite trends in terms of cold versus hot water emission: in the first case, the ground-state transitions are detected and the high-J lines are undetected, while the trend is opposite in HD 163296. We performed a spectral analysis usi…
In contrast to the water-poor inner solar system planets, stochasticity during planetary formation and order of magnitude deviations in exoplanet volatile contents suggest that rocky worlds engulfed in thick volatile ice layers are the dominant family of terrestrial analogues among the extrasolar planet population. However, the distribution of compositionally Earth-like planets remains insufficiently constrained, and it is not clear whether the solar system is a statistical outlier or can be explained by more general planetary formation processes. Here we employ numerical models of planet form…
The search for water-rich Earth-sized exoplanets around low-mass stars is rapidly gaining attention because they represent the best opportunity to characterize habitable planets in the near future. Understanding the atmospheres of these planets and determining the optimal strategy for characterizing them through transmission spectroscopy with our upcoming instrumentation is essential in order to constrain their environments. For this study, we present simulated transmission spectra of tidally locked Earth-sized ocean-covered planets around late-M to mid-K stellar spectral types, utilizing GCM …
