Researchers Discover Spatial Iron in Antarctic Snow

Wednesday, August 21, 2019 - 11:51

Researchers of Australian National University in Canberra have discovered significant amounts of a form of iron that is not naturally produced on Earth in Antarctic Snow.

According to the, researchers from Australian National University in Canberra hauled 500 kilograms of fresh snow back from Antarctica, melted it, and sifted through the particles that remained and discovered significant amounts of a form of iron that is not naturally produced on Earth.

Other scientists had previously spotted the same rare isotope of iron in deep-ocean crusts. Called iron-60, it has four more neutrons than Earth's most common form of the element. But the iron-60 in the crust likely settled on the Earth's surface millions of years ago, as opposed to what was found in fresh snow in Antarctica that had accumulated over the past two decades.

The team published their findings this week in the journal Physical Review Letters. Researchers believed that outer space objects ranging from dust to meteors regularly fall to Earth, but they are generally made of the same materials as our planet, since everything in the solar system, including the sun itself, assembled from the same building blocks billions of years ago. Because iron-60 is not among those common materials, it must have arrived from somewhere beyond the solar system.

But at the South Pole, researchers need to account for possible Earthly sources of the isotopes, such as from nuclear power plants and nuclear weapons tests. By studying additional isotopes like manganese-53, they also ruled out any significant contributions from cosmic rays, which generate iron-60 when they interact with dust and meteorites.

Dominik Koll, a physicist at Australian National University in Canberra and lead author of the study and his colleagues focused on iron-60 because it is rare, but not too rare, and it has a long lifetime, with a half-life of 2.6 million years. Many other isotopes that could have arrived from interstellar falling rocks are so unstable, with such short half-lives, that there is no way scientists could find them before they decayed away and disappeared.

Koll hopes that more data, like ice cores that reach deeper and older dust, could add more to the story. Such research would probe further into the past and could reveal more precisely when this alien dust started peppering our planet.


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