Key takeaways

  • Scientists found plutonium-244, an alien radioactive isotope, in Earth’s ocean crust.
  • Plutonium-244 was discovered alongside iron-60, indicating intense cosmic events near Earth.
  • Heavier elements like gold and uranium might be formed by neutron star mergers, not just supernovae.
  • The discovery suggests that supernovae may produce plutonium-244, or it was pushed into our solar system by such explosions.
  • The study involved scientists from multiple countries and used advanced technology to detect these rare isotopes.

Scientists are revisiting the origins of our planet’s components after discovering the first alien radioactive isotope on Earth.

The small quantities of plutonium-244 were discovered in the ocean crust with radioactive iron-60. The two isotopes provide proof of intense cosmic events that occurred millions of years ago near Earth.

Many of the heavier elements in the periodic table are created by star explosions, or supernovae, including iron, potassium, and iodine, which are essential for human life.

It was assumed that even heavier elements, such as gold, uranium, and plutonium, would need a more violent event, such as the merger of two neutron stars.

However, a research conducted by Professor Anton Wallner of The Australian National University (ANU) paints a more nuanced picture.

“The story is complicated—possibly this plutonium-244 was produced in supernova explosions or it could be left over from a much older, but even more spectacular event such as a neutron star detonation,” the study’s principal researcher, Professor Wallner, stated.

Any plutonium-244 and iron-60 that existed when the Earth formed from interstellar gas and dust over four billion years ago have long since decayed, thus any remaining traces must be the result of recent cosmic events in space.

The date of the material shows that two or more supernova explosions happened near Earth.

“Our data could be the first evidence that supernovae do indeed produce plutonium-244,” Professor Wallner explained. “Or perhaps it was already in the interstellar medium before the supernova went off, and it was pushed across the solar system together with the supernova ejecta.”

Professor Wallner also has dual appointments at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and the Technical University Dresden in Germany, and collaborated on this project with researchers from Australia, Israel, Japan, Switzerland, and Germany.

The VEGA accelerator at the Australian Nuclear Science and Technology Organisation (ANSTO) in Sydney was used to detect small quantities of plutonium-244.

The study was published in Science.


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