8
May 2003
Earth's core: Special K
The nature of the heat sources in the Earth's core has long been debated. Potassium-40 decay was suggested as one candidate on theoretical grounds over 30 years ago, but data on potassium solubility in iron have proved inconclusive. Experiments performed at high temperatures (up to 1,800 °C) and pressures (30 kilobars) now show that 40K could be a substantial heat source in the cores of Earth and Mars. Potassium is significantly soluble in iron sulphide melts at these temperatures, suggesting that it can readily enter the sulphur-bearing cores of planets. An explanation of some of the conflicting data is also proposed — polishing iron/sulphide samples for microprobe analysis using oil lubricants can result in substantial potassium loss.
Experimental evidence that potassium is a substantial
radioactive heat source in planetary cores
V. RAMA
MURTHY, WIM VAN WESTRENEN & YINGWEI FEI
Nature 423, 163–165
(2003); doi:10.1038/nature01560
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