研究人员发现，在地球传送到大气的热流中，地球内部放射性同位素衰变所产生的热量占了其中一半。新发现表明，地球形成之后的残余原始热的供应还未消耗殆尽。
作为 KamLAND合作研究组的一部分，Itaru Shimizu和同事利用日本的一个探测器测量了反微中子流。反微中子流是同位素放射性衰变过程中产生出的带电中性粒子，以不产生影响的方式穿越地球。研究人员发现在地球释放的热流中，铀-238和钍-232的放射性衰变总共产生了其中20兆兆瓦的热量。这个数值是地球释放热量的一半，表明还有另一半的热量源于自地球诞生后持续冷却所产生的热流残余。(生物谷 Bioon.com)
doi:1038/ngeo1205
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Partial radiogenic heat model for Earth revealed by geoneutrino measurements
The KamLAND
The Earth has cooled since its formation, yet the decay of radiogenic isotopes, and in particular uranium, thorium and potassium, in the planet’s interior provides a continuing heat source. The current total heat flux from the Earth to space is 44.2±1.0?TW, but the relative contributions from residual primordial heat and radiogenic decay remain uncertain. However, radiogenic decay can be estimated from the flux of geoneutrinos, electrically neutral particles that are emitted during radioactive decay and can pass through the Earth virtually unaffected. Here we combine precise measurements of the geoneutrino flux from the Kamioka Liquid-Scintillator Antineutrino Detector, Japan, with existing measurements from the Borexino detector, Italy. We find that decay of uranium-238 and thorium-232 together contribute TW to Earth’s heat flux. The neutrinos emitted from the decay of potassium-40 are below the limits of detection in our experiments, but are known to contribute 4?TW. Taken together, our observations indicate that heat from radioactive decay contributes about half of Earth’s total heat flux. We therefore conclude that Earth’s primordial heat supply has not yet been exhausted.
