This episode was supported  by Music for Scientists.

Click the link in the description to listen to the album now. {♫Intro♫} . You’re likely familiar with the fact that the Earth is surrounded by a gigantic magnetic field.

It keeps us safe from solar radiation and produces beautiful auroras at the poles as a sweet bonus. But scientists have also detected a second magnetic field surrounding the Earth, generated by its surface waters. And understanding this second field can not only help us learn more about Earth’s oceans -- it may be the key to finding new ones farther afield.

People have known about our planet’s primary magnetic field for a pretty long time. It’s generated by molten metal in the Earth’s outer core. Because the electrons in a metal are relatively free to move, that means a bunch of electric charge moving around beneath the surface of the planet.

And flowing charge creates a magnetic field. Since there’s such a huge amount of molten metal in the 2300-kilometer-thick outer core of the Earth, the magnetic field it creates is... also huge. But it turns out, superheated liquid metal isn’t the only source of magnetism on the planet.

Any flow of charge in a single direction can create a current and a corresponding magnetic field. Where there’s current, there should be a field. And it just so happens that our oceans contain a heck of a lot of charge, in the form of ions.

Ocean water is salty because it contains minerals, like sodium chloride. But those minerals dissolve in the water. The sodium and the chlorine separate from one another, into a positively charged sodium ion and a negatively charged chlorine one.

And other minerals behave in similar ways. The charge from a single ion is minuscule, but the oceans contain a lot of salt. And when that salty, ionic water flows through the Earth’s magnetic field, it creates weak electric currents, which produce their own weak magnetic field.

This had actually been predicted as far back as the 1830s, but we didn’t have the technology to spot the oceanic magnetic field until the 21st century. It was in 2018 that the European Space Agency’s SWARM satellites detected it for the first time. These three satellites orbit the Earth and make extremely precise measurements of the magnetic and electric fields surrounding the planet.

The high level of detail made it possible to distinguish the small oceanic magnetic field from the much larger geomagnetic field. This second magnetic field fluctuates with the tides -- a sure sign that it’s coming from the oceans. But it’s 20,000 times weaker than the main magnetic field, so its role in protecting our planet is minimal.

Even so, researchers hope that studying the field in the future will help us map ocean currents across the globe. That will help us to better understand how heat moves around the world. Ninety percent of all of the excess heat generated by humans is absorbed by the oceans, so being able to track where that heat is going will help predict the effects of climate change.

But being able to detect oceanic magnetic fields could also be useful beyond Earth. Faint magnetic signals coming from icy planets and moons could hint at hidden underground oceans. Researchers have already seen perturbations in Jupiter’s magnetic field around its moons.

Ganymede and Io, which could mean those moons have internal magnetic fields generated by underground oceans. So this little sibling of a magnetic field is way more than just a curiosity -- it can help us better understand our own planet and others to boot. Sometimes, people want to  express that understanding  in new ways.

Which is how Music for Scientists came to be! Created by Patrick Olson, this premiere album explores the nature of truth, consciousness, idea formation, and entropy. It's an homage   to scientists and science communicators — like us! — and an exploration into the mind-bending realities that science has unveiled.

Science and music have a lot in common, after all -- they’re both about making our world and ourselves more knowable. If that sounds like your jam, you can stream Music for Scientists on all major services or click the link below to catch the music video “For Your Love”. {♫Outro♫}.