Exoplanet interiors and habitability

Hoolst, Tim Van; Noack, Lena; Rivoldini, Attilio

doi:10.1080/23746149.2019.1630316

Cited by 19 publications

(15 citation statements)

References 180 publications

(189 reference statements)

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“…Although we consider this approach sufficient for our purposes and required precision, we stress that in recent years, significant advances have been made in the field of interior structure modeling (see Hirose et al 2013;Van Hoolst et al 2019;Taubner et al 2020, for recent reviews): these include calculations of the pressure and temperature dependent mineralogy (Dorn et al 2015) or hydration of the core and the mantle (Shah et al 2021). Furthermore, recent updates (Bouchet et al 2013;Hakim et al 2018;Mazevet et al 2019) and collections (Zeng et al 2019;Haldemann et al 2020) of equations of state were presented.…”

Section: Formation Modelsmentioning

confidence: 99%

The New Generation Planetary Population Synthesis (NGPPS)

Burn

Schlecker

Mordasini

et al. 2021

A&A

137

119

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Context. Previous theoretical works on planet formation around low-mass stars have often been limited to large planets and individual systems. As current surveys routinely detect planets down to terrestrial size in these systems, models have shifted toward a more holistic approach that reflects their diverse architectures. Aims. Here, we investigate planet formation around low-mass stars and identify differences in the statistical distribution of modeled planets. We compare the synthetic planet populations to observed exoplanets and we discuss the identified trends. Methods. We used the Generation III Bern global model of planet formation and evolution to calculate synthetic populations, while varying the central star from Solar-like stars to ultra-late M dwarfs. This model includes planetary migration, N-body interactions between embryos, accretion of planetesimals and gas, and the long-term contraction and loss of the gaseous atmospheres. Results. We find that temperate, Earth-sized planets are most frequent around early M dwarfs (0.3 M⊙–0.5 M⊙) and that they are more rare for Solar-type stars and late M dwarfs. The planetary mass distribution does not linearly scale with the disk mass. The reason behind this is attributed to the emergence of giant planets for M⋆ ≥ 0.5 M⊙, which leads to the ejection of smaller planets. Given a linear scaling of the disk mass with stellar mass, the formation of Earth-like planets is limited by the available amount of solids for ultra-late M dwarfs. For M⋆ ≥ 0.3 M⊙, however, there is sufficient mass in the majority of systems, leading to a similar amount of Exo-Earths going from M to G dwarfs. In contrast, the number of super-Earths and larger planets increases monotonically with stellar mass. We further identify a regime of disk parameters that reproduces observed M-dwarf systems such as TRAPPIST-1. However, giant planets around late M dwarfs, such as GJ 3512b, only form when type I migration is substantially reduced. Conclusions. We are able to quantify the stellar mass dependence of multi-planet systems using global simulations of planet formation and evolution. The results fare well in comparison to current observational data and predict trends that can be tested with future observations.

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Section: Formation Modelsmentioning

confidence: 99%

The New Generation Planetary Population Synthesis (NGPPS)

Burn

Schlecker

Mordasini

et al. 2021

A&A

137

119

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“…Today, scientists know many large Earth-like planets (known as super-Earths) outside the solar system. An Earth-like exoplanet with 3 Earth masses is predicted to have a core-boundary pressure of 500 GPa, while a Mercury-like exoplanet with 5 Earth masses has a similar coreboundary pressure [33], such as Luyten b [34] and Gliese 625 b [35]. For these exoplanets, Mg2SiO5H2 should exist as a water reservoir, not only before the core-mantle separation but also throughout their entire history.…”

mentioning

confidence: 99%

Ultrahigh-Pressure Magnesium Hydrosilicates as Reservoirs of Water in Early Earth

Oganov

Cui

et al. 2022

Phys. Rev. Lett.

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The origin of water on the Earth is a long-standing mystery, requiring a comprehensive search for hydrous compounds, stable at conditions of the deep Earth and made of Earthabundant elements. Previous studies usually focused on the current geothermal situation in the Earth's mantle and ignored a possible difference in the past, such as the stage of the core-mantle separation. Here, using ab initio evolutionary structure prediction, we find that only two magnesium hydrosilicate phases are stable at megabar pressures, α-Mg2SiO5H2 and β-Mg2SiO5H2, stable at 262-338 GPa and >338 GPa, respectively (all these pressures now lie within the Earth's iron core). Both are superionic conductors with quasi-one-dimensional proton diffusion at relevant conditions. In the first 50-100 million years of Earth's history, before the Earth's core was formed, these must have existed in the Earth, hosting much of Earth's water. As dense iron alloys segregated to form the Earth's core, Mg2SiO5H2 phases decomposed and released water. Thus, now-extinct Mg2SiO5H2 phases have likely contributed in a major way to the evolution of our planet.

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“…A large number of exoplanets have been discovered in recent years, including many planets whose mean densities indicate that they have rocky interiors that may be up to 10 times more massive than the Earth ( 1 ). There is interest in understanding the mineralogy of the deep interiors of such bodies where the pressure at the core–mantle boundary is predicted to reach up to 1 TPa ( 2 – 4 ).…”

mentioning

confidence: 99%

“…These pressures are expected to be reached within the mantles of rocky exoplanets of ∼4 Earth masses or greater ( 3 , 4 ). Phase changes with accompanying changes in cation coordination number may strongly affect the structure, dynamics, and heat flow in exoplanet interiors ( 1 , 5 ).…”

mentioning

confidence: 99%

Ultrahigh-pressure disordered eight-coordinated phase of Mg ₂ GeO ₄ : Analogue for super-Earth mantles

Dutta

Tracy

Yang

et al. 2022

Proc. Natl. Acad. Sci. U.S.A.

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Mg2GeO4 is important as an analog for the ultrahigh-pressure behavior of Mg2SiO4, a major component of planetary interiors. In this study, we have investigated magnesium germanate to 275 GPa and over 2,000 K using a laser-heated diamond anvil cell combined with in situ synchrotron X-ray diffraction and density functional theory (DFT) computations. The experimental results are consistent with the formation of a phase with disordered Mg and Ge, in which germanium adopts eightfold coordination with oxygen: the cubic, Th3P4-type structure. DFT computations suggest partial Mg-Ge order, resulting in a tetragonal I4¯2d structure indistinguishable from I4¯3d Th3P4 in our experiments. If applicable to silicates, the formation of this highly coordinated and intrinsically disordered phase may have important implications for the interior mineralogy of large, rocky extrasolar planets.

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Exoplanet interiors and habitability

Cited by 19 publications

References 180 publications

The New Generation Planetary Population Synthesis (NGPPS)

The New Generation Planetary Population Synthesis (NGPPS)

Ultrahigh-Pressure Magnesium Hydrosilicates as Reservoirs of Water in Early Earth

Ultrahigh-pressure disordered eight-coordinated phase of Mg ₂ GeO ₄ : Analogue for super-Earth mantles

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Exoplanet interiors and habitability

Cited by 19 publications

References 180 publications

The New Generation Planetary Population Synthesis (NGPPS)

The New Generation Planetary Population Synthesis (NGPPS)

Ultrahigh-Pressure Magnesium Hydrosilicates as Reservoirs of Water in Early Earth

Ultrahigh-pressure disordered eight-coordinated phase of Mg 2 GeO 4 : Analogue for super-Earth mantles

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Ultrahigh-pressure disordered eight-coordinated phase of Mg ₂ GeO ₄ : Analogue for super-Earth mantles