Rare interstellar radioactive material found in Antarctic snow

Interstellar radioactive material has been found in recently fallen Antarctic snow. The stunning discovery has thrilled scientists who say the rare substance fell to Earth in the form of space dust less than 20 years ago.

The discovery of the rare isotope of iron, iron-60, backs up previous research which found that the substance was generated by supernovae, strong stellar explosions, within the last few million years and should be present in geological formations on Earth. 

Researchers from Germany wanted to see if iron-60 created in stellar explosions continues to reach Earth from space. They thought there could be some in dust particles in the Local Interstellar Cloud, an area of interstellar space through which the Solar System is currently traveling, and theorized that these particles should land on Earth as it speeds past them.  

The scientists took about half a tonne of snow from near the Kohnen polar research station in the Antarctic, an uncontaminated site. They melted it in Munich and successfully used a particle accelerator to extract single iron-60 atoms from the atoms of iron found in the sample. 

The team then ruled out other possible explanations for how the iron-60 could have ended up in the snow, including the possibility it came from inside our Solar System or from nuclear testing. “By ruling out terrestrial and cosmogenic sources, we conclude that we have found, for the first time, recent iron-60 with interstellar origin in Antarctica,” the scientists wrote in Physical Review Letters.

The interstellar radioactive snow gives scientists strong evidence that some of the Local Interstellar Cloud was generated by supernovae, powerful stellar explosions. The research team will now analyze old Antarctic ice to look for an increase in iron-60 in ice from about 40,000-50,000 years ago, as that is when the Solar System is thought to have entered the Local Interstellar Cloud.

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