Plutonium-244 discovered in the Earth's crust deep under the ocean

A rare elemental called plutonium-244 has been discovered in the Earth's crust deep beneath the ocean. The discovery of the radioactive element is giving scientists clues about how heavy metals form inside stars. Scientists have researched the isotope and determined that it may have arrived on Earth in tandem with iron-60.

Iron-60 is a lighter metal that forms in supernova explosions, which is how particularly massive stars end their lives. Scientists believe finding the two metals together suggests that supernovas may create both of the heavy metals. However, they admit that it's possible that other events, like the merger of neutron stars, may responsible for some plutonium-244.

Learning how heavy metals form is particularly important for scientists and is one of the three most outstanding questions in physics. Half of the elements heavier than iron are built in the heart of stars through fusion. The other half of metals requires a higher density of free neutrons to form, meaning it must form in a more explosive environment than a star core, such as a supernova, neutron star merger, or when a black hole and a neutron star collide.

Researchers begin searching for evidence of these heavy metals on Earth to gain insight into the processes that create them. Some radioactive versions of heavy metals don't naturally occur on Earth, and scientists were specifically hunting for plutonium-244, a variation of plutonium that has a half-life of 80.6 million years.

With its long half-life, any plutonium-244 that was originally present during Earth's formation has long ago decayed, so any atoms researchers discovered would have an extraterrestrial origin. Plutonium-244 was found around 5000 feet below the Pacific Ocean in rocks that formed extremely slowly at a pace of a millimeter over 400,000 years. The sample discovered covered 10 million years.