A compositional link between rocky exoplanets and their host stars

Adibekyan, V.; Dorn, Caroline; Sousa, S. G.; Santos, N. C.; Bitsch, Bertram; Israelian, G.; Mordasini, Christoph; Barros, S. C. C.; Delgado-Mena, E.; Demangeon, O.; Faria, J. P.; Figueira, P.; Hakobyan, A. A.; Oshagh, M.; Soares, B. M. T. B.; Kunitomo, Masanobu; Takeda, Yoichi; Jofré, E.; Petrucci, R.; Martioli, Eder

doi:10.1126/science.abg8794

Cited by 112 publications

(143 citation statements)

References 89 publications

(91 reference statements)

Supporting

Mentioning

140

Contrasting

Order By: Relevance

“…In this work we extended the sample of Adibekyan et al (2021) by adding six recently discovered rocky exoplanets and studied the compositional link between rocky exoplanets and their host stars. The main results which confirm the recent findings of A21 are summarized below:…”

Section: Discussionmentioning

confidence: 99%

Composition of super-Earths, super-Mercuries, and their host stars

Adibekyan

Santos

Dorn

et al. 2021

ComBAO

View full text Add to dashboard Cite

Because of their common origin, it was assumed that the composition of planet building blocks should, to a first order, correlate with stellar atmospheric composition, especially for refractory elements. In fact, information on the relative abundance of refractory and major rock-forming elements such as Fe, Mg, Si has been commonly used to improve interior estimates for terrestrial planets. Recently Adibekyan et al. (2021) presented evidence of a tight chemical link between rocky planets and their host stars. In this study we add six recently discovered exoplanets to the sample of Adibekyan et al and re-evaluate their findings in light of these new data. We confirm that i) iron-mass fraction of rocky exoplanets correlates (but not a 1:1 relationship) with the composition of their host stars, ii) on average the iron-mass fraction of planets is higher than that of the primordial f star iron , iii) super-Mercuries are formed in disks with high iron content. Based on these results we conclude that disk-chemistry and planet formation processes play an important role in the composition, formation, and evolution of super-Earths and super-Mercuries.

show abstract

Section: Discussionmentioning

confidence: 99%

Composition of super-Earths, super-Mercuries, and their host stars

Adibekyan

Santos

Dorn

et al. 2021

ComBAO

View full text Add to dashboard Cite

show abstract

“…Further, for the refractory elements U and Th, we multiply the summand by a common factor χ rad to reflect potentially extraterrestrial variations in the abundances of these r-process elements. As surveyed in Nimmo et al (2020), U and Th abundances are conservatively expected to vary across Sun-like stars from between 30% to 300% of the solar value, which-assuming that relative mantle concentrations directly reflect relative stellar abundances (Thiabaud et al 2015;Hinkel & Unterborn 2018;Putirka & Rarick 2019;Adibekyan et al 2021)-translates to a range in q rad of 2.22-14.34 pW kg −1 at 4.5 Gyr, with the baseline value equivalent to 5.36 × 10 −12 W kg −1 . (We ignore the unconstrained variations in 40 K, a volatile isotope that in any case contributes less heating with age than refractory U and Th.)…”

Section: Heat Fluxesmentioning

confidence: 99%

“…Namely, mantle viscosities, radiogenic heating rates, and core mass fractions all relate to planetary ratios of certain major elements: viscosities decrease with Mg/Si, radiogenic heating rates increase with U/Si and Th/Si, and core mass fractions increase with Fe/O. Exoplanet compositional parameters are not completely inaccessible because refractory element ratios are expected to generally preserve themselves between a star and its planets (Thiabaud et al 2015;Hinkel & Unterborn 2018;Putirka & Rarick 2019;Adibekyan et al 2021). Although pilot work is surely needed, this useful fact means that element abundances from stellar spectra offer a promising constraint on planetary interior dynamics.…”

Section: Constraints From Astrophysical Datamentioning

confidence: 99%

Blue Marble, Stagnant Lid: Could Dynamic Topography Avert a Waterworld?

2022

View full text Add to dashboard Cite

Topography on a wet rocky exoplanet could raise land above its sea level. Although land elevation is the product of many complex processes, the large-scale topographic features on any geodynamically active planet are the expression of the convecting mantle beneath the surface. This so-called “dynamic topography” exists regardless of a planet’s tectonic regime or volcanism; its amplitude, with a few assumptions, can be estimated via numerical simulations of convection as a function of the mantle Rayleigh number. We develop new scaling relationships for dynamic topography on stagnant lid planets using 2D convection models with temperature-dependent viscosity. These scalings are applied to 1D thermal history models to explore how dynamic topography varies with exoplanetary observables over a wide parameter space. Dynamic topography amplitudes are converted to an ocean basin capacity, the minimum water volume required to flood the entire surface. Basin capacity increases less steeply with planet mass than does the amount of water itself, assuming a water inventory that is a constant planetary mass fraction. We find that dynamically supported topography alone could be sufficient to maintain subaerial land on Earth-size stagnant lid planets with surface water inventories of up to approximately 10−4 times their mass, in the most favorable thermal states. By considering only dynamic topography, which has ∼1 km amplitudes on Earth, these results represent a lower limit to the true ocean basin capacity. Our work indicates that deterministic geophysical modeling could inform the variability of land propensity on low-mass planets.

show abstract

“…However, upon the application of our devolatilization approach, both carbon and oxygen are severely depleted in rocky planets relative to their host star and therefore, a planetary (not a stellar) C/O is no longer a valid indicator of rocky planets' dominant mineral types (silicates vs. carbides). Due to the refractory nature (and similar T c 50 ; Lodders 2003;Wood et al 2019) of Mg and Si, their ratio in a star is not significantly altered through the devolatilization process (Wang et al 2019a) and thus is still a good first-order proxy for Mg/Si in a rocky planet around the host star (Schulze et al 2021;Adibekyan et al 2021;Thiabaud et al 2014;Delgado Mena et al 2010;Bond et al 2010).…”

Section: Key Geochemical Ratiosmentioning

confidence: 99%

“…Observations of the chemical compositions of rocky bodies in the Solar System (Wang et al 2019a;Sossi & Fegley 2018;Carlson et al 2014;Grossman & Larimer 1974) and of polluted white dwarfs (Harrison et al 2021(Harrison et al , 2018Doyle et al 2019) lend support to the idea that the chemical composition of "terrestrial" (silicate+metal dominated) planets generally reflects that of their host stars for refractory elements, whereas this expression breaks down for volatile elements (Schulze et al 2021;Adibekyan et al 2021). This discrepancy can be explained by devolatilization processes (Wang et al 2019a;Sossi et al 2019;Norris & Wood 2017;Hin et al 2017) that occurred during the formation and early evolution of the terrestrial planets of our best star-planet sample, the Solar System.…”

Section: Introductionmentioning

confidence: 98%

A model Earth-sized planet in the habitable zone of $α$ Centauri A/B

Wang,

Lineweaver,

Quanz

et al. 2021

Preprint

View full text Add to dashboard Cite

The bulk chemical composition and interior structure of rocky exoplanets are of fundamental importance to understanding their long-term evolution and potential habitability. Observations of the chemical compositions of the solar system rocky bodies and of other planetary systems have increasingly shown a concordant picture that the chemical composition of rocky planets reflects that of their host stars for refractory elements, whereas this expression breaks down for volatiles. This behavior is explained by devolatilization during planetary formation and early evolution. Here, we apply a devolatilization model calibrated with the solar system bodies to the chemical composition of our nearest Sun-like stars -α Centauri A and B -to estimate the bulk composition of any habitable-zone rocky planet in this binary system ("α-Cen-Earth"). Through further modeling of likely planetary interiors and early atmospheres, we find that compared to Earth, such a planet is expected to have (i) a reduced (primitive) mantle that is similarly dominated by silicates albeit enriched in carbon-bearing species (graphite/diamond); (ii) a slightly larger iron core, with a core mass fraction of 38.4 +4.7 −5.1 wt% (cf. Earth's 32.5 ± 0.3 wt%); (iii) an equivalent water-storage capacity; and (iv) a CO 2 -CH 4 -H 2 O-dominated early atmosphere that resembles that of Archean Earth. Further taking into account its ∼ 25% lower intrinsic radiogenic heating from long-lived radionuclides, an ancient α-Cen-Earth (∼ 1.5-2.5 Gyr older than Earth) is expected

show abstract

A compositional link between rocky exoplanets and their host stars

Cited by 112 publications

References 89 publications

Composition of super-Earths, super-Mercuries, and their host stars

Composition of super-Earths, super-Mercuries, and their host stars

Blue Marble, Stagnant Lid: Could Dynamic Topography Avert a Waterworld?

A model Earth-sized planet in the habitable zone of $α$ Centauri A/B

Contact Info

Product

Resources

About