Radiogenic Heating and Its Influence on Rocky Planet Dynamos and Habitability
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Radiogenic Heating and Its Influence on Rocky Planet Dynamos and Habitability. / Nimmo, Francis; Primack, Joel; Faber, S. M.; Ramirez-Ruiz, Enrico; Safarzadeh, Mohammadtaher.
In: Astrophysical Journal Letters, Vol. 903, No. 2, L37, 11.2020.Research output: Contribution to journal › Letter › Research › peer-review
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TY - JOUR
T1 - Radiogenic Heating and Its Influence on Rocky Planet Dynamos and Habitability
AU - Nimmo, Francis
AU - Primack, Joel
AU - Faber, S. M.
AU - Ramirez-Ruiz, Enrico
AU - Safarzadeh, Mohammadtaher
PY - 2020/11
Y1 - 2020/11
N2 - The thermal evolution of rocky planets on geological timescales (Gyr) depends on the heat input from the long-lived radiogenic elements potassium, thorium, and uranium. Concentrations of the latter two in rocky planet mantles are likely to vary by up to an order of magnitude between different planetary systems because Th and U, like other heavy r-process elements, are produced by rare stellar processes. Here we discuss the effects of these variations on the thermal evolution of an Earth-size planet, using a 1D parameterized convection model. Assuming Th and U abundances consistent with geochemical models of the Bulk Silicate Earth based on chondritic meteorites, we find that Earth had just enough radiogenic heating to maintain a persistent dynamo. According to this model, Earth-like planets of stars with higher abundances of heavy r-process elements, indicated by the relative abundance of europium in their spectra, are likely to have lacked a dynamo for a significant fraction of their lifetimes, with potentially negative consequences for hosting a biosphere. Because the qualitative outcomes of our 1D model are strongly dependent on the treatment of viscosity, further investigations using fully 3D convection models are desirable.
AB - The thermal evolution of rocky planets on geological timescales (Gyr) depends on the heat input from the long-lived radiogenic elements potassium, thorium, and uranium. Concentrations of the latter two in rocky planet mantles are likely to vary by up to an order of magnitude between different planetary systems because Th and U, like other heavy r-process elements, are produced by rare stellar processes. Here we discuss the effects of these variations on the thermal evolution of an Earth-size planet, using a 1D parameterized convection model. Assuming Th and U abundances consistent with geochemical models of the Bulk Silicate Earth based on chondritic meteorites, we find that Earth had just enough radiogenic heating to maintain a persistent dynamo. According to this model, Earth-like planets of stars with higher abundances of heavy r-process elements, indicated by the relative abundance of europium in their spectra, are likely to have lacked a dynamo for a significant fraction of their lifetimes, with potentially negative consequences for hosting a biosphere. Because the qualitative outcomes of our 1D model are strongly dependent on the treatment of viscosity, further investigations using fully 3D convection models are desirable.
KW - Extrasolar rocky planets
KW - Earth (planet)
KW - Super Earths
KW - Magnetic fields
KW - Exoplanet evolution
KW - R-process
KW - Stellar nucleosynthesis
KW - Astrobiology
KW - EVOLUTION
KW - EARTH
KW - GEODYNAMO
KW - ELEMENTS
KW - CORE
KW - POTASSIUM
KW - TECTONICS
KW - MERGERS
U2 - 10.3847/2041-8213/abc251
DO - 10.3847/2041-8213/abc251
M3 - Letter
VL - 903
JO - The Astrophysical Journal Letters
JF - The Astrophysical Journal Letters
SN - 2041-8205
IS - 2
M1 - L37
ER -
ID: 252039437