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According to the study authors, "the cenotectic plays a central role in the 'endgame' of planetary oceans. As large water-rich planetary bodies cool over geologic timescales or with loss of internal heating such as tidal dissipation or radiogenic heating, their oceans will gradually freeze from top to bottom, until complete solidification is achieved. This effect is particularly interesting in the case of large icy moons like Ganymede, Callisto, and Titan, but also for cold ocean exoplanets like Trappist 1e-g and water-rich rogue exoplanets."

“A lot of rocks that are in Australia can produce hydrogen. We have a lot of old granites that are now close to the subsurface and can generate hydrogen through radiogenic processes.”

Collisions between tectonic plates buried these sedimentary rocks deep in the Earth's crust where radiogenic heat released by the shale triggered melting of the lower crust.

The researchers analyzed uranium, thorium and potassium concentrations from hundreds of samples of rocks from the Archean period, when the cratons formed, to assess the radiogenic heat productivity based on actual rock compositions.

"Previously people have looked at and considered the effects of changing radiogenic heat production through time," Smye said.