UC-Santa Cruz’ Natalie Batalha is director of the university’s Astrobiology Initiative, whose multidisciplinary work is designed to produce the kind of widespread collaboration found in this paper.
The authors find that Earth “had just enough radiogenic heating to maintain a persistent dynamo.” And that has implications for the atmosphere. Within the Earth, there are enough radioactive elements to generate a persistent ‘geodynamo,’ in which molten iron and nickel in motion in the planet’s outer core produce electric currents, forming a magnetic field as the Earth rotates. That quote is from the paper, whose lead author is Francis Nimmo, and it points to the key role of radiogenic heat in the mantle. Similarly, heat production will control the mantle temperature and thus the rate of silicate melting and volcanism. Since mantle radiogenic heat production controls how much heat is extracted from the core, it will also influence the presence or absence of a dynamo. In the rocky planets, magnetic fields are generated by convection in a metallic core, which in turn is driven by heat extracted into the mantle (Nimmo 2015 Labrosse 2015 Boujibar et al.
Let’s carry this line of thought further, though, as the authors of a new paper out of UC-Santa Cruz do, and point out that these heavy elements are necessary to create a magnetic field like Earth’s, which protects us from damaging radiation. And creating that dynamo seems to depend on the radioactive decay of thorium and uranium, generating internal heating and driving plate tectonics. A planetary dynamo may be a key factor in creating the conditions needed for life.
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