[en] Full text: Computing the chemical composition of planet is a growing need for planetary formation models and for the search of habitable planets as they are probably related. Previous works have been investigating the chemical composition of planet, combining dynamical process of planetary formation and chemistry. However, either these studies have only focused on the volatile content of the planets (CO,H₂O,CO₂,CH₄,...) either the composition of the planets have been determined in a non self-consistent manner. we also investigate the production of refractory organic compounds that previous work ignored. We present here results of calculations of chemical compositions of planets with the combination of the planetary formation model of Alibert et al. 2005, 2013, Mordasini et al. 2009, Fortier et al. 2013 and the condensation sequence theory for a nebula of solar composition. Combination has been carried with self-consistency with the planetary formation model. We show that the results are consistent with C/O and Mg/Si ratios in the Sun and that organics can represent up to 30% of the composition of a planet. The self-consistency is also of most importance to form a wide variety of planets. (author)

[en] Full text: We present results of the effect of pollution due to planetesimals' disruption in the envelope of protoplanets. We show that taking into account the change of composition due to the addition of elements heavier that H and He in the equation of state and in the opacities, affects dramatically the critical core mass. Furthermore, we compute the timescale for gas accretion onto super critical planets. Comparing this timescale to the one of solid accretion, we discuss the implications on the formation of giant planets. (author)

[en] Full text: Planet formation models have been developed during the last years in order to try to reproduce and predict observations of the solar system and extra solar planets. Using a modular planetary system formation model combining an extended core-accretion model including migration, disc evolution and gap formation with an N-Body part for the dynamical interactions we perform population synthesis calculations in order to investigate the effect of the formation of more than one planet in the same protoplanetary disc. We show the modifications of masses and semi-major axis through competition and gravitational interactions varying the number of forming planets. (author)

[en] Common features of all carbonaceous chondrite groups are invariant refractory element ratios, depletions of moderately volatile elements as a function of their condensation temperature (T _C), and strongly depleted highly volatile element concentrations independent of T _C. The depletion of volatile elements with respect to the bulk solar system composition requires a separation of gas from solids in the solar nebula. Several models have been proposed to explain the decoupling of gas and solids, but not all are compatible with astrophysical, chemical, and petrologic constraints. Here existing physical models are integrated with measured element concentrations, measured and modeled physical properties of protoplanetary disks, and planetary-scale nucleosynthetic and stable isotope variations to establish a conceptual model for the condensation and accretion of elements into planetesimals. In this model, the chemical composition of chondrites is established by element condensation in a cooling solar nebula that changed its surface density as a function of time and temperature. The model predicts peak temperatures at the condensation sites of about 1400 K that consequently decreased due to a diminishing heat source originating from viscous heating and radiation, accompanied by continuous removal of gas from the nebula surface by photoevaporation. The coupled evolution of condensing solids from a nebula of diminishing surface density resulted in a pattern of decreasing moderately volatile abundances with decreasing T _C. The reduction of nebula opacity due to the chondrule-forming process significantly increased nebula cooling rates and led to the near-chondritic relative abundances of highly volatile elements observed in carbonaceous chondrites.

[en] The search for small planets orbiting late M dwarfs holds the promise of detecting Earth-size planets for which their atmospheres could be characterized within the next decade. The recent discovery of TRAPPIST-1 entertains hope that these systems are common around hosts located at the bottom of the main sequence. In this Letter, we investigate the ability of the repurposed Kepler mission ( K2 ) to probe planetary systems similar to TRAPPIST-1. We perform a consistent data analysis of 189 spectroscopically confirmed M5.5 to M9 late M dwarfs from Campaigns 1–6 to search for planet candidates and inject transit signals with properties matching TRAPPIST-1b and c. We find no transiting planet candidates across our K2 sample. Our injection tests show that K2 is able to recover both TRAPPIST-1 planets for 10% of the sample only, mainly because of the inefficient throughput at red wavelengths resulting in Poisson-limited performance for these targets. Increasing injected planetary radii to match GJ 1214b’s size yields a recovery rate of 70%. The strength of K2 is its ability to probe a large number of cool hosts across the different campaigns, out of which the recovery rate of 10% may turn into bona fide detections of TRAPPIST-1-like systems within the next two years.

[en] We analyze the emission spectrum of the hot Jupiter WASP-12b using our HELIOS-R retrieval code and HELIOS-K opacity calculator. When interpreting Hubble and Spitzer data, the retrieval outcomes are found to be prior-dominated. When the prior distributions of the molecular abundances are assumed to be log-uniform, the volume mixing ratio of HCN is found to be implausibly high. A VULCAN chemical kinetics model of WASP-12b suggests that chemical equilibrium is a reasonable assumption even when atmospheric mixing is implausibly rigorous. Guided by (exo)planet formation theory, we set Gaussian priors on the elemental abundances of carbon, oxygen, and nitrogen with the Gaussian peaks being centered on the measured C/H, O/H, and N/H values of the star. By enforcing chemical equilibrium, we find substellar O/H and stellar to slightly superstellar C/H for the dayside atmosphere of WASP-12b. The superstellar carbon-to-oxygen ratio is just above unity, regardless of whether clouds are included in the retrieval analysis, consistent with Madhusudhan et al. Furthermore, whether a temperature inversion exists in the atmosphere depends on one’s assumption for the Gaussian width of the priors. Our retrieved posterior distributions are consistent with the formation of WASP-12b in a solar-composition protoplanetary disk, beyond the water iceline, via gravitational instability or pebble accretion (without core erosion) and migration inward to its present orbital location via a disk-free mechanism, and are inconsistent with both in situ formation and core accretion with disk migration, as predicted by Madhusudhan et al. We predict that the interpretation of James Webb Space Telescope WASP-12b data will not be prior-dominated.

[en] We calculate the minimum mass of heavy elements required in the envelopes of Jupiter and Saturn to match the observed oversolar abundances of volatiles. Because the clathration efficiency remains unknown in the solar nebula, we have considered a set of sequences of ice formation in which the fraction of water available for clathration is varied between 0 and 100%. In all the cases considered, we assume that the water abundance remains homogeneous whatever the heliocentric distance in the nebula and directly derives from a gas phase of solar composition. Planetesimals then form in the feeding zones of Jupiter and Saturn from the agglomeration of clathrates and pure condensates in proportions fixed by the clathration efficiency. A fraction of Kr and Xe may have been sequestrated by the H⁺₃ ion in the form of stable XeH⁺₃ and KrH⁺₃ complexes in the solar nebula gas phase, thus implying the formation of at least partly Xe- and Kr-impoverished planetesimals in the feeding zones of Jupiter and Saturn. These planetesimals were subsequently accreted and vaporized into the hydrogen envelopes of Jupiter and Saturn, thus engendering volatiles enrichments in their atmospheres, with respect to hydrogen. Taking into account both refractory and volatile components, and assuming plausible molecular mixing ratios in the gas phase of the outer solar nebula, we show that it is possible to match the observed enrichments in Jupiter and Saturn, whatever the clathration efficiency. Our calculations predict that the O/H enrichment decreases from ∼ 5.5 to 5.1 times (O/H)_sun in the envelope of Jupiter and from 15.2 to 14.1 times (O/H)_sun in the envelope of Saturn with the growing clathration efficiency in the solar nebula. As a result, the minimum mass of ices needed to be injected in the envelope of Jupiter decreases from ∼ 20.0 to 18.6 M ₊, including a mass of water diminishing from 10.4 to 9.3 M ₊. In the same conditions, the minimum mass of ices needed in the envelope of Saturn decreases from ∼ 16.7 to 15.6 M ₊, including a mass of water diminishing from 8.6 to 7.7 M ₊. The accretion of planetesimals with ices to rocks ratios ∼ 1 in the envelope of Jupiter, namely a value derived from the bulk densities of Ganymede and Callisto, remains compatible with the mass of heavy elements predicted by interior models. On the other hand, the accretion of planetesimals with similar ice-to-rock in the envelope of Saturn implies a mass of heavy elements greater than the one predicted by interior models, unless a substantial fraction of the accreted rock and water sedimented onto the core of the planet during its evolution.

[en] We describe a scenario of Titan's formation matching the constraints imposed by its current atmospheric composition. Assuming that the abundances of all elements, including oxygen, are solar in the outer nebula, we show that the icy planetesimals were agglomerated in the feeding zone of Saturn from a mixture of clathrates with multiple guest species, so-called stochiometric hydrates such as ammonia hydrate, and pure condensates. We also use a statistical thermodynamic approach to constrain the composition of multiple guest clathrates formed in the solar nebula. We then infer that krypton and xenon, that are expected to condense in the 20-30 K temperature range in the solar nebula, are trapped in clathrates at higher temperatures than 50 K. Once formed, these ices either were accreted by Saturn or remained embedded in its surrounding subnebula until they found their way into the regular satellites growing around Saturn. In order to explain the carbon monoxide and primordial argon deficiencies of Titan's atmosphere, we suggest that the satellite was formed from icy planetesimals initially produced in the solar nebula and that were partially devolatilized at a temperature not exceeding ∼50 K during their migration within Saturn's subnebula. The observed deficiencies of Titan's atmosphere in krypton and xenon could result from other processes that may have occurred both prior to or after the completion of Titan. Thus, krypton and xenon may have been sequestrated in the form of XH⁺₃ complexes in the solar nebula gas phase, causing the formation of noble gas-poor planetesimals ultimately accreted by Titan. Alternatively, krypton and xenon may have also been trapped efficiently in clathrates located on the satellite's surface or in its atmospheric haze. We finally discuss the subsequent observations that would allow us to determine which of these processes is the most likely.