Iron-60 falls,
sprinkling stardust on pure snow.
Is this Philip’s Dust?
Particles of extraterrestrial dust enter the Earth’s atmosphere all the time, coming from asteroids or comets. Yet some is thought to come from supernova explosions and could help us understand the history of our solar neighbourhood. How can researchers detect these particles?
The key lies in a rare isotope, iron-60, that has no natural sources on Earth. But measuring abundance of iron-60 is easier said than done. One previous study has found iron-60 in deep sea sediment deposits but new research by Koll et al (2019) suggests that pure, untouched Antarctic snow is another viable source.
The team collected pure snow that was less than 20 years old, melted it, filtered out the solids and incinerated the residues. They then used mass spectrometry to measure the presence of iron-60 and manganese-53. By comparing the relative abundances of these two isotopes the researchers were able to demonstrate that the source of the iron-60 was interstellar dust, ruling out other potential sources such as cosmic radiation, nuclear weapons tests or reactor accidents.
The process opens the way for researchers to measure iron-60 abundance in older snow samples to get an idea of where and when the supernova occurred and when our Solar System entered the local interstellar cloud.
The final line of this sciku is a reference to Philip Pullman’s His Dark Materials, in a scene near the very start of the trilogy where Lord Asriel shows images of Dust taken in the Arctic:
“And the streams of Dust…”
Chapter 2, The Northern Lights by Philip Pullman.
” – Come from the sky, and bathe him in what looks like light.”
Original research: http://dx.doi.org/10.1103/PhysRevLett.123.072701