Radiogenic power and geoneutrino luminosity of the Earth and other terrestrial bodies through time
2019
We report the Earth's rate of radiogenic heat production and (anti)neutrino luminosity from geologically relevant short-lived radionuclides (SLR) and long-lived radionuclides (LLR) using decay constants from the geological community, updated nuclear physics parameters, and calculations of the $\beta$ spectra. We carefully account for all branches in $^{40}$K decay using the updated $\beta^-$ energy spectrum from physics and an updated branching ratio from geological studies. We track the time evolution of the radiogenic power and luminosity of the Earth over the last 4.57 billion years, assuming an absolute abundance for the refractory elements in the silicate Earth and key volatile/refractory element ratios (e.g., Fe/Al, K/U, and Rb/Sr) to set the abundance levels for the moderately volatile elements. The relevant decays for the present-day heat production in the Earth ($19.9\pm3.0$ TW) are from $^{40}$K, $^{87}$Rb, $^{147}$Sm, $^{232}$Th, $^{235}$U, and $^{238}$U. A simple formula for evaluation at arbitrary planetary composition is offered. The radiogenic heating rate of earth-like material at Solar System formation was some 10$^3$ to 10$^4$ times greater than present-day values, largely due to decay of $^{26}$Al in the silicate fraction, which was the dominant radiogenic heat source for the first $\sim10$\,My. Decay of $^{60}$Fe contributed a non-negligible amount of heating during the first $\sim15$\,My after CAI (Calcium Aluminum Inclusion) formation, interestingly within the time frame of core--mantle segregation. Using factors and equations presented here, one can calculate the first-order thermal and (anti)neutrino luminosity history of various size bodies in the solar system and exoplanets.
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