A team of scientists took 500 kilograms of Antarctic snow, melted it and sifted through the leftover particles. Their analysis yielded a surprise: Snow contains significant amounts of a form of iron not found on Earth.
Other scientists have previously discovered that rare iron isotope in deep ocean crust. Called iron-60 . But iron-60 in the crust likely settled on the Earth’s surface millions of years ago, in contrast to what is found in new Antarctic snow that has accumulated over the past two decades.
The Kohnen Research Station in Antarctica is close to the site of the snow samples in which iron-60 was found.
Outer space objects ranging from dust to meteors often fall to Earth, but they are usually made of the same materials as our planet, since everything in the solar system, including the Sun, is assembled. assembled from the same “building” billions of years ago. But iron-60 is not among those common materials, so it must have come from somewhere outside the solar system.
“A meteor is a very rare event. The smaller the size of the object, the more abundant it is. Dust particles will fall to the Earth’s surface more often, but taking them out from the myriad other particles around is a difficult task,” said Harvard astronomer Avi Loeb.
In Antarctica, researchers need to account for possible Earth-based isotope sources, such as from nuclear power plants and nuclear weapons testing. The amount of iron-60 can be produced by nuclear reactors, tests and accidents such as the 2011 disaster in Fukushima, and researchers have calculated only a very small amount.
Stars eject a bunch of tiny particles over their lifetime, in addition to all the light and heat. But as stars get younger, they often give off lighter metals. Iron-60 and its “cousin” , iron-56 is usually the last element a star can produce while still generating energy, and after the last steps of life, it explodes . However, only stars tens of times more massive than our Sun can produce iron isotopes. However, that means the iron-60 found in Antarctica is from outside the solar system.