The "dust" of a star that exploded millions of years ago was found in the Antarctic snow

Australian scientists have discovered a significant amount of a rare isotope that is not found on Earth.

Experts say that there is no chance that the iron isotope 60 was made by humans, which suggests that it was delivered to Earth by an impact with a space stone.

Iron 60 has four more neutrons than iron and is found in the Earth's crust, but not normally in our atmosphere.

Scientists suggest that a rock containing material, coming from a star that exploded millions of years ago, must have had an impact on the Earth's atmosphere.

This would have scattered the star dust, which then fell to the ground when it was captured in snowflakes.

Scroll for the video

"Making these measurements is very difficult," said Bernhard Peucker-Ehrenbrink, a geochemist at the Woods Hole Oceanographic Institution, in a press release. "You are essentially counting individual atoms."

The researchers melted about 100 pounds of snow from Antarctica, examining what had been left behind.

They ruled out the creation of 60 iron from nuclear power plants and weapons testing, estimating that only a small amount could reach the South Pole.

They also studied other isotopes to remove the iron 60 generated by cosmic rays after interacting with dust or meteorites.

Interstellar meteorites are rare, according to Avi Loeb, an astronomer at Harvard, but "the smaller the object, the more abundant it is".

The researchers therefore claim that the source of iron 60 must be a supernova.

"Not so close as killing us, but not too far to be diluted in space," said lead researcher Dominik Koll, a physicist at the Australian National University.

Mr. Koll explained that, in this case, the particles could have been collected during the passage of the Earth in the local interstellar medium (ISM), a region of the space of 30 light-years traversed by our solar system.

Spectacular displays of this interstellar medium can be found in star forming regions where new stars are being created.

Planetary nebulae and supernova remnants where ancient stars return much of their mass in space also

In the region located just around the sun, in a hundred parsecs, which houses the local interstellar medium.

Here we find a series of warm clouds of modest density, partially ionized. More research is needed to understand where and when Iron 60 arrived on Earth.

It has a half-life of 2.6 million years – according to Dr. Koll, it will take more data and ice cores that penetrate deeper into the planet, reaching older dusts.

The complete results of the study were published in the journal Physical Review Letters.