This dust stood out because it contains an iron isotope called iron-60, which is commonly released by supernovas but very rare on Earth.
When the scientists examined the incinerated dust using an accelerator mass spectrometer, they detected the rare iron-60 isotope — a relic of an ancient supernova.
Our solar system is currently passing through a large cloud of space dust known as the Local Interstellar Cloud (LIC), and grains from this cloud found on Earth could reveal much about how our sun and its planets interact with cosmic dust.
Irradiated dust shed by planets and other bodies can hold iron-60, but exposure to cosmic radiation also creates another isotope: manganese-53.
The researchers compared ratios of iron-60 and manganese-53 in the Antarctic grains, finding that the quantity of manganese was much lower than it would have been if the dust were local.
There may have been iron-60 on our planet during its infancy, but all of this rare isotope has long since decayed on Earth, the researchers wrote in the study.
Nuclear bomb tests could have created and dispersed iron-60 across the planet, but calculations showed that the quantity of the isotope produced by such tests would have been much lower than the amount of iron-60 found in Antarctica's snow.