Y: Don, have you ever wondered what’s in Antarctic snow besides frozen water?
D: I can’t say I have, Yaël.
Y: Antarctica’s snows trap cosmic dust, raining down from space. Some comes from beyond our solar system.
D: So, if scientists gathered lots of Antarctic snow and melted and filtered it, they’d have a sample of cosmic dust?
Y: Yes, that’s right. In a study reported in 2019 a team of German scientists gathered snow at an Antarctic base that was far from the coast, at a high altitude, to minimize Earthly contamination. They analyzed the material they extracted from eleven hundred pounds of snow with one of the world’s most sensitive mass spectrometers and discovered traces of a rare isotope of iron, called iron-60. They think this isotope was produced in the nuclear reactions of a supernova explosion.
D: But Yaël, how can the scientists be sure that the iron-60 really comes from a supernova?
Y: Scientists only know of one other way iron-60 can be made. Dust particles in deep space are exposed to cosmic radiation, and bombardment with this radiation can also make iron-60. But, this process produces a rare isotope of manganese along with the iron-60. So, the scientists compared the amount of iron-60 in their samples with the amount of the manganese isotope. They found the ratio of iron-60 was way too high for all of it to have been produced by cosmic rays, and concluded the rest came from a supernova.
D: That means that a supernova in our region of the galaxy produced some of the dust now raining down on Earth.