Helium isotopes reveal hidden stores of geothermal energy.

Most geothermal power plants exploit the relatively rare but easy to spot hot water associated with volcanoes, limiting geothermal energy to a niche role in meeting global energy demand. It works well in Iceland and a few other places, but geothermal energy is a largely untapped resource in much of the world, in part because, in the absence of a volcano or hot springs, it’s hard to find the right spot to tap into the resource. Last week, a pair of geochemists published a report in Science showing that the ultrasensitive detection of traces of helium at the surface using mass spectrometers may hold the key to sniffing out the best sites of this hidden heat.