Abstract
Ariel will mark the dawn of a new era as the first large-scale survey characterising exoplanetary atmospheres with science objectives to address fundamental questions about planetary composition, evolution and formation. In this study, we explore the detectability of atmospheres vaporised from magma oceans on dry, rocky Super-Earths orbiting very close to their host stars. The detection of such atmospheres would provide a definitive piece of evidence for rocky planets but are challenging measurements with currently available instruments due to their small spectral signatures. However, some of the hottest planets are believed to have atmospheres composed of vaporised rock, such as Na and SiO, with spectral signatures bright enough to be detected through eclipse observations with planned space-based telescopes. In this study, we find that rocky super-Earths with a irradiation temperature of 3000 K and a distance from Earth of up to 20 pc, as well as planets hotter than 3500 K and closer than 50 pc, have SiO features which are potentially detectable in eclipse spectra observed with Ariel.
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References
Al-Refaie, A. F., Changeat, Q., Waldmann, I. P., Tinetti, G.: TauREx III: A fast, dynamic and extendable framework for retrievals. arXiv e-prints arXiv:1912.07759 (2019)
Asimow, P.D., Ghiorso, M.S.: Algorithmic modifications extending MELTS to calculate subsolidus phase relations. Am. Mineral. 83, 1127–1132 (1998)
Barclay, T., Pepper, J., Quintana, E. V.: A revised exoplanet yield from the Transiting Exoplanet Survey Satellite (TESS). Astrophys. J. Suppl. Ser. 239, 2 (2018)
Barragán, O., Gandolfi, D., Dai, F., et al.: K2-141 b. A 5-M⊕ super-Earth transiting a K7 V star every 6.7 h. Astron. Astrophys. 612, A95 (2018)
Bourrier, V., Dumusque, X., Dorn, C., et al.: The 55 Cnc system reassessed. Astron. Astrophys. 619, A1 (2018)
Changeat, Q., Edwards, B., Waldmann, I.P., Tinetti, G., et al.: Towards a more complex description of chemical profiles in exoplanets retrievals: A 2-layer parameterisation. The Astron. J. 886, 39 (2019)
Changeat, Q., Keyte, L., Waldmann, I.P., Tinetti, G., et al.: Impact of planetary mass uncertainties on exoplanet atmospheric retrievals. Astrophys. J. 896 (2020)
Changeat, Q., Al-Refaie, A., Mugnai, L.V., et al.: Alfnoor: A retrieval simulation of the Ariel target list. The Astron. J. 160, 80 (2020)
Demory, B.-O., Gillon, M., de Wit, J., et al.: A map of the large day-night temperature gradient of a super-Earth exoplanet. Nature 532, 207–209 (2016)
Dragomir, D., Matthews, J. M., Winn, J. N., Rowe, J. F.: New MOST photometry of the 55 Cnc system. Formation, detection, and characterization of extrasolar habitable planets 52 (2014)
Edwards, B., Mugnai, L., Tinetti, G., Pascale, E., Sarkar, S.: An updated study of potential targets for Ariel. The Astron. J. 157, 242 (2019)
Ehrenreich, D., Bourrier, V., Bonfils, X., et al.: Hint of a transiting extended atmosphere on 55 Cnc b. Astron. Astrophys. 547, A18 (2012)
Elkins-Tanton, L. T., Seager, S.: Coreless terrestrial exoplanets. Astrophysical Journal 688, 628 (2008)
Essack, Z., Seager, S., Pajusalu, M.: Low-albedo surfaces of lava worlds. Astrophys. J. 898 (2020)
Espinoza, N., Brahm, R., Henning, T., et al.: HD 213885b: a transiting 1-d-period super-Earth with an Earth-like composition around a bright (V = 7.9) star unveiled by TESS. Mon. Not. R. Astron. Soc. 491, 2982 (2020)
Esteves, L. J., de Mooij, E. J. W., Jayawardhana, R., et al.: A search for water in a super-earth atmosphere: high-resolution optical spectroscopy of 55Cancri e. Astron. J. 153, 268 (2017)
Feroz, F., Hobson, M.P., Bridges, M., et al.: MultiNest: an efficient and robust Bayesian inference tool for cosmology and particle physics. Nonthly Notices of the RAS 398, 1601–1614 (2009)
Fulton, B.J., Petigura, E.A., Howard, A.W., et al.: The California-Kepler survey. III. A gap in the radius distribution of small planets. The Astron. J. 154, 109 (2017)
Gardner, J.P., Mather, J.C., Clampin, M., et al.: The James Webb space telescope. Space Sci. Rev. 123, 485 (2006)
Gillon, M., Demory, B.-O., Benneke, B., et al.: Improved precision on the radius of the nearby super-Earth 55 Cnc e. Astron. Astrophys. 539, A28 (2012)
Ghiorso, M. S., Sack, R. O.: Chemical mass transfer in magmatic processes IV. A revised and internally consistent thermodynamic model for the interpolation and extrapolation of liquid-solid equilibria in magmatic systems at elevated temperatures and pressures. Contrib. Mineral. Petrol. 119, 197–212 (1995)
Gordon, S., McBride, B. J.: Computer program for calculation of complex chemical equilibrium compositions and applications NASA reference publication 1311 (1996)
Hammond, M., Pierrehumbert, R. T.: Linking the climate and thermal phase curve of 55 Cancri e. Astrophys. J. 849 (2017)
Hu, R., Seager, S.: Photochemistry in terrestrial exoplanet atmospheres. III. Photochemistry and thermochemistry in thick atmospheres on super Earths and mini Neptunes. Astrophys. J. 784, 63 (2014)
Ito, Y., Ikoma, M., et al.: Theoretical emission spectra of atmospheres of hot rocky super-Earths. Astrophys. J. 801, 144 (2015)
Jin, S., Mordasini, C.: Compositional imprints in density-distance-time: A rocky composition for close-in low-mass exoplanets from the location of the valley of evaporation. Astrophys. J. 853, 163 (2018)
Kendrew, S., Scheithauer, S., Bouchet, P., et al.: The mid-infrared instrument for the James Webb space telescope, IV: The low-resolution spectrometer. Publ. Astron. Soc. Pac. 127, 623 (2015)
Kurosaki, K., Ikoma, M., Hori, Y.: Impact of photo-evaporative mass loss on masses and radii of water-rich sub/super-Earths. Astronomy & Astrophysics 562, A80 (2014)
Kunimoto, M., Matthews, J. M.: Searching the entirety of Kepler data. II. Occurrence Rate estimates for FGK stars. The Astron. J. 159, 248 (2020)
Lopez, E. D.: Born dry in the photoevaporation desert: Kepler’s ultra-short-period planets formed water-poor. Monthly Notices 472, 245 (2017)
Lupu, RE, et al.: The atmospheres of Earthlike planets after giant impact events. Astrophys. J. 784, 27 (2014)
Lothringer, J. D., Barman, T., Koskinen, T.: Extremely irradiated hot Jupiters: Non-oxide inversions, H− opacity, and thermal dissociation of molecules. Astrophys. J. 866 (2018)
Madhusudhan, N., Lee, K. K. M., Mousis, O.: A possible carbon-rich interior in super-Earth 55 Cancri e. Astrophys. J. Lett. 759, L40 (2012)
Mayo, A.W., Vanderburg, A., Latham, D.W., et al.: 275 Candidates and 149 validated planets orbiting bright stars in K2 campaigns 0-10. The Astron. J. 155, 136 (2018)
Miguel, Y., Kaltenegger, L., Fegley, B., Schaefer, L.: Compositions of hot super-Earth atmospheres: Exploring Kepler candidates. The Astrophys. J. 742, L19 (2011)
Miguel, Y.: Observability of molecular species in a nitrogen dominated atmosphere for 55 Cancri e. Mon. Not. R. Astron. Soc. 482, 2893–2901 (2019)
Miyagoshi, T., Kameyama, M., Ogawa, M.: Effects of adiabatic compression on thermal convection in super-Earths of various sizes. Earth, Planets, and Space 70, 200 (2018)
Morbidelli, A., Raymond, S. N.: Challenges in planet formation. J Geophys Res (Planets) 121, 1962 (2016)
Miozzi, F., Morard, G., Antonangeli, D., et al.: Equation of state of SiC at extreme conditions: new insight into the interior of carbon-rich exoplanets. J Geophys Res (Planets) 123, 2295 (2018)
Modirrousta-Galian, D., Ito, Y., Micela, G: Exploring super-earth surfaces: Albedo of near-airless magma ocean planets and topography. arXiv e-prints (2020)
Modirrousta-Galian, D., Locci, D., Tinetti, G., Micela, G.: Hot super-Earths with hydrogen atmospheres: A model explaining their paradoxical existence. Astrophys. J. 888 (2020)
Mugnai, L.V., Pascale, E., Edwards, B., et al.: ArielRad: the Ariel radiometric model. Exp. Astron. 50, 303–328 (2020)
Nelson, B.E., Ford, E.B., Wright, J.T., et al.: The 55 Cnc planetary system: fully self-consistent N-body constraints and a dynamical analysis. Mon. Not. R. Astron. Soc. 441, 442 (2014)
Owen, J. E., Wu, Y.: The evaporation valley in the Kepler planets. Astrophys. J. 847, 29 (2017)
Rogers, L. A., Seager, S.: . Astrophysical Journal 712, 974 (2010)
Sanchis-Ojeda, R., Rappaport, S., Winn, J. N., Kotson, M. C., Levine, A., El Mellah, I.: A study of the shortest-period planets found with Kepler. Astrophys. J. 787, 47 (2014)
Schaefer, L., Fegley, B.: Chemistry of silicate atmospheres of evaporating super-Earths. Astrophys. J. 703, L113 (2009)
Schaefer, L., Lodders, K., Fegley, B.: Vaporization of the Earth: Application to exoplanet atmospheres. Astrophys. J. 755, 41 (2012)
Seager, S., Mallén-Ornelas, G.: A unique solution of planet and star parameters from an extrasolar planet transit light curve. Astrophys. J. 585, 1038 (2003)
Tackley, P. J., Ammann, M., Brodholt, J. P., et al.: Mantle dynamics in super-Earths: post-perovskite rheology and self-regulation of viscosity. Icarus 225, 50 (2013)
Tinetti, G., Tinetti, G., Drossart, P., Eccleston, P., et al.: A chemical survey of exoplanets with Ariel. Exp. Astron. 46, 135 (2018)
Toon, O. B., McKay, C. P., Ackerman, T. P., Santhanam, K.: Rapid calculation of radiative heating rates and photodissociation rates in inhomogeneous multiple scattering atmospheres. J. Geophys. Res. 94, 16287–16301 (1989)
Tsiaras, A., Rocchetto, M., Waldmann, I. P., et al.: Detection of an Atmosphere around the Super-Earth 55 Cancri e. Astrophys. J. 820, 99 (2016)
Traub, W. A., Oppenheimer, B. R.: Direct imaging of exoplanets. Exoplanets 111 (2010)
Valencia, D., Ikoma, M., Guillot, T., Nettlemann, N.: Composition and fate of short-period super-Earths: The case of CoRoT-7b. Lunar and planetary science conference 1872 (2010)
Zhang, X., Showman, A. P.: Effects of bulk composition on the atmospheric dynamics on close-in exoplanets. Astrophys. J. 836 (2017)
Zilinskas, M., Miguel, Y., Mollière, P., Tsai, S.-M.: Atmospheric compositions and observability of nitrogen-dominated ultra-short-period super-Earths. Mon. Not. R. Astron. Soc. 494, 1490–1506 (2020)
Acknowledgments
We appreciate Dr. Renyu Hu for providing us with the calculation data of emission spectra of the hydrogen-rich and water-rich atmospheres that are used in Fig. 7. This project has received funding from the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 776403, ExoplANETS A). Furthermore, we acknowledge funding by the Science and Technology Funding Council (STFC) grants: ST/K502406/1, ST/P000282/1, ST/P002153/1, and ST/S002634/1.
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Appendix: 55-Cancri e retrieval simulations
Appendix: 55-Cancri e retrieval simulations
In order to investigate the feasibility to detect SiO with future telescopes, we simulate the atmosphere of a 55-Cancri e like planet using the model from [25] and estimating the Ariel noise with the Ariel Radiometric Model (ArielRad) from [42]. The observations are assumed at Tier-2 resolution [11][8] and we investigate the combined transits of 20, 40 and 80 visits. The corresponding SSiO signal strength for these visits can be found in Fig. 4 and we note that a value of 1σ is obtained between 20 and 40 combined transits. We then performed an atmospheric retrieval using TauREx3 on the 3 cases, assuming a plane parallel atmosphere with 100 layers up to 10− 5 Pa. The surface pressure was fixed to its true value. Since a surface pressure and the molar fraction of a gas have the same effect on its optical depth, only the partial pressure of the gas inducing a spectral signature can be retrieved from atmospheric spectra in principle. Note that, however, the surface pressures of mineral atmospheres can be determined from our atmospheric model using retrieved surface temperature.
Since the Ariel spectra obtained for a mineral atmosphere have a relatively low information content, we fit the simulated spectra using a simplified retrieval model. The planetary radius and mass were fixed [7] to the literature values as more accurate constraints can be obtain from Radial Velocity and Transit measurements. For the temperature structure, we retrieved a heuristic profile comprised of 3 freely moving temperature-pressure points located at the surface, at 1 Pa and 10− 5 Pa. The atmosphere was assumed to be composed of H2, He and SiO with the molecular ratio \(X_{He}/X_{H_{2}}\) fixed to solar values and the ratio \(X_{SiO}/X_{H_{2}}\) being the only free parameter of the chemistry.
To explore the parameter space we use the Nested Sampling algorithm MultiNest [17] with 1000 live points and an evidence tolerance of 0.5.
From those retrievals, we find that the SiO spectra feature at 4.5μm is difficult to capture with 20 combined Ariel observations. For this case, the posterior distribution shows hints of the SiO signal, but a large tail is observed towards the low abundances, which would not allow to definitively conclude for this case. In the 40 and 80 observations cases, however, the noise is greatly reduced and a clear lower limit on the molecular ratio is observed (log SiO/H2 = 0.4\(^{+1.5}_{-1.0}\)). While the precise abundances can’t be obtained, a retrieval analysis would give strong indications in favor of a mineral atmosphere. The retrieved temperature structure for this example follows the input profile, but large differences are noticeable due to the differences between the forward and retrieval models. This is known to lead to biases that could potentially be mitigated when interpreting the results using self-consistent models or replacing the retrieval model with a more realistic scenario [6, 8]. We note that for hotter planets, the detection of an SiO signal with Ariel would be much easier. This is because the 4-μm-SiO signals deviate from BBref at three or four Ariel wavelength-bins for hotter planets (Fig. 5), while it deviates from BBref at the two bins (\(\sim 4.0\mu \)m and \(\sim 4.3\mu \)m) for the 55 Cnc e case. On top of this, when comparing with other models for the magma and atmosphere composition (see Fig. 7), the mineral atmosphere case appears as the worst case scenario since bigger features are observed in the cases of Hydrogen rich or Water rich atmosphere. In practice, it is likely that much less than 20 visits would be need for 55-Cancri e like planet to rule out the Hydrogen and Water rich cases.
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Ito, Y., Changeat, Q., Edwards, B. et al. Detectability of Rocky-Vapour atmospheres on super-Earths with Ariel. Exp Astron 53, 357–374 (2022). https://doi.org/10.1007/s10686-020-09693-6
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DOI: https://doi.org/10.1007/s10686-020-09693-6