Radiogenic Power and Geoneutrino Luminosity of the Earth and Other Terrestrial Bodies Through Time

Abstract

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 β spectra. 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 ± 3.0 TW) are from 40K, 87Rb, 147Sm, 232Th, 235U, and 238U. Given element concentrations in kg‐element/kg‐rock and density ρ in kg/m3, a simplified equation to calculate the present‐day heat production in a rock is h[μW m−3]=ρ3.387×10−3K+0.01139Rb+0.04595Sm+26.18Th+98.29U The radiogenic heating rate of Earth‐like material at solar system formation was some 103 to 104 times greater than present‐day values, largely due to decay of 26Al in the silicate fraction, which was the dominant radiogenic heat source for the first ∼10 Ma. Assuming instantaneous Earth formation, the upper bound on radiogenic energy supplied by the most powerful short‐lived radionuclide 26Al (t1/2 = 0.7 Ma) is 5.5×1031 J, which is comparable (within a factor of a few) to the planet's gravitational binding energy.

Geoneutrinos and geoscience: an intriguing joint-venture

“…Production rates ν and ν for 40 K are higher than previous reports because of the recently updated 40 K's half-life T 1/2 estimation [14], which is, respectively, 2.6%, 2.3% and 1.1% lower than what reported in [15][16][17] *The 238 U decay chain contains β − decays (e.g., 210 Tl) producing geoneutrinos with energies > 3.26 MeV. Historically, these are not considered for geoneutrino analyses because of their low intensities, impossible to observe through current experiments…”

“…The radiogenic heat production inside the Earth is due to the energy released by the decays of radioactive nuclides which indeed play a starring role in the comprehension of geodynamical processes. Neglecting a fractional contribution coming from rare radionuclides ( 87 Rb, 138 La, 147 Sm, 176 Lu, 187 Re and 190 Pt), the 99.5% of the present Earth's radiogenic heat production is due to the decay (or the decay chains) of 40 K, 232 Th, 235 U and 238 U, long-lived radionuclides (T 1/2 > 10 8 years) created at the time of the Solar System formation and still extant now [121]. Due to their different halflives, the relative amounts of heat-producing nuclides, and in turn their contribution to radiogenic budget, changed with time.…”

“…In Fig. 21a, the Earth radiogenic power is plotted with respect to the time for the last 3.7 Gyr adopting a BSE composition of the medium-H model reported in [38] following the updated a(K)/a(U) from [123] (Sect. 7.3).…”

Terrestrial planet compositions controlled by accretion disk magnetic field

“…g Desch et al (2018). h Heat production in the bulk silicate planets are calculated from chondritic (Al/Th) mass = 2.81×10 5 and (Th/U) mass = 3.7, planetary (K/Th) mass = 7000, 3700, and 5300 for Mercury, Earth, and Mars, respectively (Peplowski et al 2011;Arevalo Jr. et al 2009;Taylor et al 2006), and an equation from McDonough et al (2020). pW = 10 −12 W; TW = 10 12 W.…”

“…Based on the compositional estimates given in Table 1, chondritic ratios of refractory elements, and planetary K/Th values, we have calculated the present-day radiogenic heating rate (pW kg −1 ) and total planetary radiogenic power (TW) according to the method outlined in McDonough et al (2020). The estimated bulk uranium contents of Mercury, Earth, and Mars are 7, 13, and 15 ppb (10 −9 kg/kg).…”