[en] The TRAPPIST-1 system contains seven roughly Earth-sized planets locked in a multiresonant orbital configuration[SUP]1,2[/SUP], which has enabled precise measurements of the planets' masses and constrained their compositions[SUP]3[/SUP]. Here we use the system's fragile orbital structure to place robust upper limits on the planets' bombardment histories. We use N-body simulations to show how perturbations from additional objects can break the multiresonant configuration by either triggering dynamical instability or simply removing the planets from resonance. The planets cannot have interacted with more than ~5% of one Earth mass (M[SUB]⊕[/SUB]) in planetesimals—or a single rogue planet more massive than Earth's Moon—without disrupting their resonant orbital structure. This implies an upper limit of 10[SUP]−4[/SUP]M[SUB]⊕[/SUB] to 10[SUP]−2[/SUP] M[SUB]⊕[/SUB] of late accretion on each planet since the dispersal of the system's gaseous disk. This is comparable to (or less than) the late accretion on Earth after the Moon-forming impact[SUP]4,5[/SUP], and demonstrates that the growth of the TRAPPIST-1 planets was complete in just a few million years, roughly an order of magnitude faster than that of the Earth[SUP]6,7[/SUP]. Our results imply that any large water reservoirs on the TRAPPIST-1 planets must have been incorporated during their formation in the gaseous disk.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Raymond, Sean N.; Laboratoire d'Astrophysique de Bordeaux, Université de Bordeaux, CNRS, Pessac, France
Izidoro, Andre; Department of Earth, Environmental and Planetary Sciences, Rice University, Houston, TX, USA
Bolmont, Emeline; Observatoire de Genève, Université de Genève, Sauverny, Switzerland
Dorn, Caroline; University of Zurich, Institute of Computational Sciences, Zurich, Switzerland
Selsis, Franck; Laboratoire d'Astrophysique de Bordeaux, Université de Bordeaux, CNRS, Pessac, France
Turbet, Martin; Observatoire de Genève, Université de Genève, Sauverny, Switzerland
Agol, Eric; Department of Astronomy, University of Washington, Seattle, WA, USA
Barth, Patrick; Centre for Exoplanet Science, University of St Andrews, St Andrews, UK ; SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, UK ; School of Earth and Environmental Sciences, University of St Andrews, St Andrews, UK
Carone, Ludmila; Max Planck Institute for Astronomy, Heidelberg, Germany
Dasgupta, Rajdeep; Department of Earth, Environmental and Planetary Sciences, Rice University, Houston, TX, USA
Gillon, Michaël ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Exotic
Grimm, Simon L.; Center for Space and Habitability, University of Bern, Bern, Switzerland)
Language :
English
Title :
An upper limit on late accretion and water delivery in the TRAPPIST-1 exoplanet system
Gillon, M. et al. Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1. Nature 542, 456–460 (2017).
Luger, R. et al. A seven-planet resonant chain in TRAPPIST-1. Nat. Astron. 1, 0129 (2017).
Agol, E. et al. Refining the transit-timing and photometric analysis of TRAPPIST-1: masses, radii, densities, dynamics, and ephemerides. Planet. Sci. J. 2, 1 (2021).
Day, J. M. D., Pearson, D. G. & Taylor, L. A. Highly siderophile element constraints on accretion and differentiation of the Earth-Moon system. Science 315, 217–219 (2007).
Walker, R. J. Highly siderophile elements in the Earth, Moon and Mars: update and implications for planetary accretion and differentiation. Geochemistry 69, 101–125 (2009).
Wood, B. J. & Halliday, A. N. Cooling of the Earth and core formation after the giant impact. Nature 437, 1345–1348 (2005).
Kleine, T. et al. Hf-W chronology of the accretion and early evolution of asteroids and terrestrial planets. Geochim. Cosmochim. Acta 73, 5150–5188 (2009).
Fernandez, J. A. & Ip, W. Some dynamical aspects of the accretion of Uranus and Neptune: the exchange of orbital angular momentum with planetesimals. Icarus 58, 109–120 (1984).
Izidoro, A. et al. Formation of planetary systems by pebble accretion and migration. Hot super-Earth systems from breaking compact resonant chains. Astron. Astrophys. 650, A152 (2021).
Kral, Q. et al. Cometary impactors on the TRAPPIST-1 planets can destroy all planetary atmospheres and rebuild secondary atmospheres on planets f, g, and h. Mon. Not. R. Astron. Soc. 479, 2649–2672 (2018).
Došović, V., Novaković, B., Vukotić, B. & Ćirković, M. M. Water transport throughout the TRAPPIST-1 system: the role of planetesimals. Mon. Not. R. Astron. Soc. 499, 4626–4637 (2020).
Chambers, J. E. A hybrid symplectic integrator that permits close encounters between massive bodies. Mon. Not. R. Astron. Soc. 304, 793–799 (1999).
Gonzales, E. C. et al. A reanalysis of the fundamental parameters and age of TRAPPIST-1. Astrophys. J. 886, 131 (2019).
Tamayo, D., Rein, H., Petrovich, C. & Murray, N. Convergent migration renders TRAPPIST-1 long-lived. Astrophys. J. Lett. 840, L19 (2017).
Morbidelli, A., Lunine, J. I., O’Brien, D. P., Raymond, S. N. & Walsh, K. J. Building terrestrial planets. Annu. Rev. Earth Planet. Sci. 40, 251–275 (2012).
Dauphas, N. & Pourmand, A. Hf–W–Th evidence for rapid growth of Mars and its status as a planetary embryo. Nature 473, 489–492 (2011).
Marchi, S., Canup, R. M. & Walker, R. J. Heterogeneous delivery of silicate and metal to the Earth by large planetesimals. Nat. Geosci. 11, 77–81 (2018).
Ormel, C. W., Liu, B. & Schoonenberg, D. Formation of TRAPPIST-1 and other compact systems. Astron. Astrophys. 604, A1 (2017).
Papaloizou, J. C. B., Szuszkiewicz, E. & Terquem, C. The TRAPPIST-1 system: orbital evolution, tidal dissipation, formation and habitability. Mon. Not. R. Astron. Soc. 476, 5032–5056 (2018).
Coleman, G. A. L., Leleu, A., Alibert, Y. & Benz, W. Pebbles versus planetesimals: the case of Trappist-1. Astron. Astrophys. 631, A7 (2019).
Miguel, Y., Cridland, A., Ormel, C. W., Fortney, J. J. & Ida, S. Diverse outcomes of planet formation and composition around low-mass stars and brown dwarfs. Mon. Not. R. Astron. Soc. 491, 1998–2009 (2020).
Terquem, C. & Papaloizou, J. C. B. Migration and the formation of systems of hot super-Earths and Neptunes. Astrophys. J. 654, 1110–1120 (2007).
Dorn, C. et al. A generalized Bayesian inference method for constraining the interiors of super Earths and sub-Neptunes. Astron. Astrophys. 597, A37 (2017).
Turbet, M. et al. Revised mass-radius relationships for water-rich rocky planets more irradiated than the runaway greenhouse limit. Astron. Astrophys. 638, A41 (2020).
Dorn, C., Mosegaard, K., Grimm, S. L. & Alibert, Y. Interior characterization in multiplanetary systems: TRAPPIST-1. Astrophys. J. 865, 20 (2018).
Unterborn, C. T., Desch, S. J., Hinkel, N. R. & Lorenzo, A. Inward migration of the TRAPPIST-1 planets as inferred from their water-rich compositions. Nat. Astron. 2, 297–302 (2018).
Barth, P. et al. Magma ocean evolution of the TRAPPIST-1 planets. Astrobiology 10.1089/ast.2020.2277 (2021).
Acuña, L. et al. Characterisation of the hydrospheres of TRAPPIST-1 planets. Astron. Astrophys. 647, A53 (2021).
Alexander, C. M. O., McKeegan, K. D. & Altwegg, K. Water reservoirs in small planetary bodies: meteorites, asteroids, and comets. Space Sci. Rev. 214, 36 (2018).
Schlichting, H. E., Sari, R. & Yalinewich, A. Atmospheric mass loss during planet formation: the importance of planetesimal impacts. Icarus 247, 81–94 (2015).
Marty, B. The origins and concentrations of water, carbon, nitrogen and noble gases on Earth. Earth Planet. Sci. Lett. 313, 56–66 (2012).
Mulders, G. D., Ciesla, F. J., Min, M. & Pascucci, I. The snow line in viscous disks around low-mass stars: implications for water delivery to terrestrial planets in the habitable zone. Astrophys. J. 807, 9 (2015).
Ramirez, R. M. & Kaltenegger, L. The habitable zones of pre-main-sequence stars. Astrophys. J. 797, L25 (2014).
Tian, F. & Ida, S. Water contents of Earth-mass planets around M dwarfs. Nat. Geosci. 8, 177–180 (2015).
Luger, R. & Barnes, R. Extreme water loss and abiotic O2 buildup on planets throughout the habitable zones of M dwarfs. Astrobiology 15, 119–143 (2015).
Bolmont, E. et al. Water loss from terrestrial planets orbiting ultracool dwarfs: implications for the planets of TRAPPIST-1. Mon. Not. R. Astron. Soc. 464, 3728–3741 (2017).
Kislyakova, K. G. et al. Magma oceans and enhanced volcanism on TRAPPIST-1 planets due to induction heating. Nat. Astron. 1, 878–885 (2017).
Leleu, A. et al. Six transiting planets and a chain of Laplace resonances in TOI-178. Astron. Astrophys. 649, A26 (2021).
Mills, S. M. et al. A resonant chain of four transiting, sub-Neptune planets. Nature 533, 509–512 (2016).
IAU Resolution B5: Definition of a Planet in the Solar System (IAU, 2006).
Gillon, M. et al. Temperate Earth-sized planets transiting a nearby ultracool dwarf star. Nature 533, 221–224 (2016).
Burgasser, A. J. & Mamajek, E. E. On the age of the TRAPPIST-1 system. Astrophys. J. 845, 110 (2017).
Mann, A. W. et al. How to constrain your M dwarf. II. The mass-luminosity-metallicity relation from 0.075 to 0.70 solar masses. Astrophys. J. 871, 63 (2019).
Ducrot, E. et al. TRAPPIST-1: global results of the Spitzer Exploration Science Program Red Worlds. Astron. Astrophys. 640, A112 (2020).
Lee, M. H. & Peale, S. J. Dynamics and origin of the 2:1 orbital resonances of the GJ 876 planets. Astrophys. J. 567, 596–609 (2002).
Cresswell, P., Dirksen, G., Kley, W. & Nelson, R. P. On the evolution of eccentric and inclined protoplanets embedded in protoplanetary disks. Astron. Astrophys. 473, 329–342 (2007).
Izidoro, A. et al. Breaking the chains: hot super-Earth systems from migration and disruption of compact resonant chains. Mon. Not. R. Astron. Soc. 470, 1750–1770 (2017).
Bottke, W. F., Walker, R. J., Day, J. M. D., Nesvorny, D. & Elkins-Tanton, L. Stochastic late accretion to Earth, the Moon, and Mars. Science 330, 1527–1530 (2010).
Raymond, S. N., Schlichting, H. E., Hersant, F. & Selsis, F. Dynamical and collisional constraints on a stochastic late veneer on the terrestrial planets. Icarus 226, 671–681 (2013).
Morbidelli, A. & Wood, B. J. in The Early Earth: Accretion and Differentiation (eds Badro, J. & Walter, M.) 71–82 (Geophysical Monograph Series, Vol. 212, John Wiley & Sons, 2015).
Levison, H. F. & Duncan, M. J. The long-term dynamical behavior of short-period comets. Icarus 108, 18–36 (1994).
Boss, A. P. et al. Astrometric constraints on the masses of long-period gas giant planets in the TRAPPIST-1 planetary system. Astron. J. 154, 103 (2017).
Jontof-Hutter, D., Truong, V. H., Ford, E. B., Robertson, P. & Terrien, R. C. Dynamical constraints on nontransiting planets orbiting TRAPPIST-1. Astron. J. 155, 239 (2018).
Ogihara, M. & Ida, S. N-body simulations of planetary accretion around M dwarf stars. Astrophys. J. 699, 824–838 (2009).
McNeil, D. S. & Nelson, R. P. On the formation of hot Neptunes and super-Earths. Mon. Not. R. Astron. Soc. 401, 1691–1708 (2010).
Ida, S. & Lin, D. N. C. Toward a deterministic model of planetary formation. VI. Dynamical interaction and coagulation of multiple rocky embryos and super-Earth systems around solar-type stars. Astrophys. J. 719, 810–830 (2010).
Cossou, C., Raymond, S. N., Hersant, F. & Pierens, A. Hot super-Earths and giant planet cores from different migration histories. Astron. Astrophys. 569, A56 (2014).
Schoonenberg, D., Liu, B., Ormel, C. W. & Dorn, C. Pebble-driven planet formation for TRAPPIST-1 and other compact systems. Astron. Astrophys. 627, A149 (2019).
Lin, Y.-C., Matsumoto, Y. & Gu, P.-G. Formation of multiple-planet systems in resonant chains around M dwarfs. Astrophys. J. 907, 81 (2021).
Murray, C. D. & Dermott, S. F. Solar System Dynamics (Cambridge Univ. Press, 1999).
Hadden, S. & Lithwick, Y. A criterion for the onset of chaos in systems of two eccentric planets. Astron. J. 156, 95 (2018).
Wyatt, M. C., Bonsor, A., Jackson, A. P., Marino, S. & Shannon, A. How to design a planetary system for different scattering outcomes: giant impact sweet spot, maximizing exocomets, scattered discs. Mon. Not. R. Astron. Soc. 464, 3385–3407 (2017).
A’Hearn, M. F. Comets as building blocks. Annu. Rev. Astron. Astrophys. 49, 281–299 (2011).
Choukroun, M. et al. Dust-to-gas and refractory-to-ice mass ratios of comet 67P/Churyumov-Gerasimenko from Rosetta observations. Space Sci. Rev. 216, 44 (2020).
Bolmont, E., Raymond, S. N. & Leconte, J. Tidal evolution of planets around brown dwarfs. Astron. Astrophys. 535, A94 (2011).
Baraffe, I., Homeier, D., Allard, F. & Chabrier, G. New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit. Astron. Astrophys. 577, A42 (2015).
Hansen, B. M. S. Calibration of equilibrium tide theory for extrasolar planet systems. Astrophys. J. 723, 285–299 (2010).
Bolmont, E., Raymond, S. N., Leconte, J. & Matt, S. P. Effect of the stellar spin history on the tidal evolution of close-in planets. Astron. Astrophys. 544, A124 (2012).
Bolmont, E. & Mathis, S. Effect of the rotation and tidal dissipation history of stars on the evolution of close-in planets. Celest. Mech. Dynam. Astron. 126, 275–296 (2016).
Blanco-Cuaresma, S. & Bolmont, E. Studying tidal effects in planetary systems with Posidonius. A N-body simulator written in Rust. Zenodo https://doi.org/10.5281/zenodo.1095095 (2017).
Bolmont, E. et al. Impact of tides on the transit-timing fits to the TRAPPIST-1 system. Astron. Astrophys. 635, A117 (2020).
Herbst, W., Eislöffel, J., Mundt, R. & Scholz, A. in Protostars and Planets V (eds Reipurth, B. et al.) 297–311 (Univ. Arizona Press, 2007).
Bolmont, E., Raymond, S. N., Leconte, J. & Matt, S. P. Effect of the stellar spin history on the tidal evolution of close-in planets. Astron. Astrophys. 544, A124 (2012).
Hay, H. C. F. C. & Matsuyama, I. Tides between the TRAPPIST-1 planets. Astrophys. J. 875, 22 (2019).
Grimm, S. L. et al. The nature of the TRAPPIST-1 exoplanets. Astron. Astrophys. 613, A68 (2018).
Dorn, C. et al. Can we constrain the interior structure of rocky exoplanets from mass and radius measurements? Astron. Astrophys. 577, A83 (2015).
Sotin, C., Grasset, O. & Mocquet, A. Mass–radius curve for extrasolar Earth-like planets and ocean planets. Icarus 191, 337–351 (2007).
Lodders, K., Palme, H. & Gail, H.-P. Abundances of the elements in the solar system. Preprint at https://arxiv.org/abs/0901.1149 (2009).
Doyle, A. E., Young, E. D., Klein, B., Zuckerman, B. & Schlichting, H. E. Oxygen fugacities of extrasolar rocks: evidence for an Earth-like geochemistry of exoplanets. Science 366, 356–359 (2019).
Hakim, K. et al. A new ab initio equation of state of hcp-Fe and its implication on the interior structure and mass-radius relations of rocky super-Earths. Icarus 313, 61–78 (2018).
Haldemann, J., Alibert, Y., Mordasini, C. & Benz, W. Aqua: a collection of H2O equations of state for planetary models. Astron. Astrophys. 643, A105 (2020).
Haar, L., Gallagher, J. & Kell, G. NBS/NRC Steam Tables Thermodynamic and Transport Properties and Computer Programs for Vapor and Liquid States of Water in SI Units (Hemisphere, 1984).
Turbet, M., Ehrenreich, D., Lovis, C., Bolmont, E. & Fauchez, T. The runaway greenhouse radius inflation effect. An observational diagnostic to probe water on Earth-sized planets and test the habitable zone concept. Astron. Astrophys. 628, A12 (2019).
Shah, O., Alibert, Y., Helled, R. & Mezger, K. Internal water storage capacity of terrestrial planets and the effect of hydration on the M-R relation. Preprint at https://arxiv.org/abs/2012.06455 (2020).
Mamajek, E. E. Initial conditions of planet formation: lifetimes of primordial disks. AIP Conf. Proc. 1158, 3–10 (2009).
Turbet, M. et al. Modeling climate diversity, tidal dynamics and the fate of volatiles on TRAPPIST-1 planets. Astron. Astrophys. 612, A86 (2018).
