Our Solar System is currently passing through the Local Interstellar Cloud, a region of highly diluted gas and dust between the stars. On its path, Earth continuously accumulates iron-60, a rare radioactive isotope of iron produced in stellar explosions. This has now been confirmed by an international research team led by the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) through the analysis of Antarctic ice tens of thousands of years old. From the steady but time-varying influx, the researchers conclude that the radioactive isotope has been stored within the cloud since a long-past stellar explosion.

Researchers studying Antarctic ice cores have discovered traces of the rare iron isotope iron-60, which provides insights into Earth's movement through the cosmos. Iron-60 is produced in extreme events like supernova explosions and cannot form naturally on Earth in significant amounts. The team, led by nuclear astrophysicist Dominik Koll, found iron-60 in ice cores dating from 40,000 to 81,000 years ago, as well as in recent snowfall, indicating the Solar System has been passing through a cloud of supernova debris. By analyzing 295 kilograms of Antarctic ice, the researchers identified variations in iron-60 concentrations, suggesting that the Local Interstellar Cloud through which the Solar System moves has regions of differing density. This ice core record effectively serves as a 'flight log' of Earth's journey through this cloud over the past 80,000 years. The study supports the idea that the Local Interstellar Cloud may be composed of material from supernova events and highlights the potential for using isotopes in ice to map interstellar environments. The findings were published in Physical Review Letters, providing a new method to study the structure and history of cosmic dust clouds from material available on Earth.