A formation pathway for terrestrial planets with moderate water content involving atmospheric-volatile recycling

Abstract

Of the many recently discovered terrestrial exoplanets, some are expected to harbor moderate water mass fractions of a few percent. The formation pathways that can produce planets with these water mass fractions are not fully understood. Here, we use the code chemcomp, which consists of a semi-analytical 1D protoplanetary disk model harboring a migrating and accreting planet, to model the growth and composition of planets with moderate water mass fractions by pebble accretion in a protoplanetary disk around a TRAPPIST-1 analog star. This star is accompanied by seven terrestrial planets, of which the outer four planets likely contain water mass fractions of between 1\% and 10\%. We adopt a published model that considers the evaporation of pebbles in the planetary envelope, from where recycling flows can transport the volatile vapor back into the disk. We find that with this model, the planetary water content depends on the influx rate of pebbles onto the planet. A decreasing pebble influx with time reduces the envelope temperature and consequently allows the formation of planets with moderate water mass fractions as inferred for the outer TRAPPIST-1 planets for a number of different simulation configurations. This is further evidence that the recycling of vapor is an important component of planet formation needed to explain the vast and diverse population of exoplanets.

arXiv commentAccepted by A&A, 19 pages, 8 figures

References in corpus (63)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• The chemical composition of the Sun
• Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1
• New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit
• The origins and concentrations of water, carbon, nitrogen and noble gases on Earth
• Using FU Orionis Outbursts to Constrain Self-Regulated Protostellar Disk Models
• A simple model for the evolution of the dust population in protoplanetary disks
• Mass-Radius Relationships for Solid Exoplanets
• Coagulation, fragmentation and radial motion of solid particles in protoplanetary disks
• Temperate Earth-sized planets transiting a nearby ultracool dwarf star
• Growth Model Interpretation of Planet Size Distribution
• A Steeper than Linear Disk Mass-Stellar Mass Scaling Relation
• Protoplanetary Disk Structures in Ophiuchus II: Extension to Fainter Sources
• Breaking the Chains: Hot Super-Earth systems from migration and disruption of compact resonant chains
• How to Constrain Your M dwarf II: the mass-luminosity-metallicity relation from 0.075 to 0.70$M_{\odot }$
• Can we constrain interior structure of rocky exoplanets from mass and radius measurements?
• An ALMA Survey of Protoplanetary Disks in the $\sigma$ Orionis Cluster
• Pebble isolation mass --- scaling law and implications for the formation of super-Earths and gas giants
• Water Vapor and Clouds on the Habitable-Zone Sub-Neptune Exoplanet K2-18b
• Planetesimal formation starts at the snow line
• Water vapour in the atmosphere of the habitable-zone eight Earth-mass planet K2-18 b
• Dust size distributions in coagulation/fragmentation equilibrium: Numerical solutions and analytical fits
• Planetesimal formation near the snowline: in or out?
• Fossilized condensation lines in the Solar System protoplanetary disk
• On the Minimum Core Mass for Giant Planet Formation at Wide Separations
• Hydrodynamics of Embedded Planets' First Atmospheres. II. A Rapid Recycling of Atmospheric Gas
• Planet heating prevents inward migration of planetary cores
• How drifting and evaporating pebbles shape giant planets I: Heavy element content and atmospheric C/O
• Formation of TRAPPIST-1 and other compact systems
• Reduced gas accretion on super-Earths and ice giants
• Super-Earth masses sculpted by pebble isolation around stars of different masses
• Hydrodynamics of embedded planets' first atmospheres - III. The role of radiation transport for super-Earth planets
• Coorbital thermal torques on low-mass protoplanets
• Grain opacity and the bulk composition of extrasolar planets. II. An analytical model for the grain opacity in protoplanetary atmospheres
• The opacity of grains in protoplanetary atmospheres
• The New Generation Planetary Population Synthesis (NGPPS). III. Warm super-Earths and cold Jupiters: A weak occurrence correlation, but with a strong architecture-composition link
• Rocky super-Earths or waterworlds: the interplay of planet migration, pebble accretion and disc evolution
• Pebble-driven planet formation for TRAPPIST-1 and other compact systems
• The Exoplanet Radius Valley from Gas-driven Planet Migration and Breaking of Resonant Chains
• Suppression of atmospheric recycling of planets embedded in a protoplanetary disc by buoyancy barrier
• Capture and Evolution of Planetesimals in Circumjovian Disks
• The TRAPPIST-1 system: Orbital evolution, tidal dissipation, formation and habitability
• Dusty tails of evaporating exoplanets. I. Constraints on the dust composition
• Effect of nucleation on icy pebble growth in protoplanetary discs
• How planets grow by pebble accretion II: Analytical calculations on the evolution of polluted envelopes
• Global 3D radiation-hydrodynamic simulations of gas accretion: The opacity dependent growth of Saturn-mass planets
• Thermal torque effects on the migration of growing low-mass planets
• An upper limit on late accretion and water delivery in the Trappist-1 exoplanet system
• Eccentricity excitation and merging of planetary embryos heated by pebble accretion
• Steady State by Recycling prevents Premature Collapse of Protoplanetary Atmospheres
• Eyes on K2-3: A system of three likely sub-Neptunes characterized with HARPS-N and HARPS
• On water delivery in the inner solar nebula: Monte Carlo simulations of forsterite hydration
• Recycling of the first atmospheres of embedded planets: Dependence on core mass and optical depth
• Atmospheric Recyling of Volatiles by Pebble-Accreting Planets
• The physics of protoplanetesimal dust agglomerates. X. High-velocity collisions between small and large dust agglomerates as growth barrier
• Forming super-Mercuries: The role of stellar abundances
• How planets grow by pebble accretion IV: Envelope opacity trends from sedimenting dust and pebbles
• The water-ice line as a birthplace of planets: Implications of a species-dependent dust fragmentation threshold
• Dynamical Evolution of the Earth-Moon Progenitors - Whence Theia?
• Influence of migration models and thermal torque on planetary growth in the pebble accretion scenario
• TRAPPIST-1: Dynamical analysis of the transit-timing variations and origin of the resonant chain
• Influence of grain sizes and composition on the contraction rates of planetary envelopes and on planetary migration
• Accretion, winds and outflows in young stars

Cited by in corpus (6)

• Linking the primordial composition of planet building disks to the present-day composition of rocky exoplanets
• Diversity of disc viscosities can explain the period ratios of resonant and non-resonant systems of hot super-Earths and mini-Neptunes
• Born Dry or Born Wet? A Palette of Water Growth Histories in TRAPPIST-1 Analogs and Compact Planetary Systems
• From CO${}_2$- to H${}_2$O-dominated atmospheres and back -- How mixed outgassing changes the volatile distribution in magma oceans around M dwarf stars
• Long-term evolution of the temperature structure in magnetized protoplanetary disks and its implication for the dichotomy of planetary composition
• An Evolving Cosmic Shoreline and Sandbar Bounding the Rocky Airless Valley