Radioactive dust from a supernova landed in Antarctica from a star that exploded into a supernova millions of years ago, where it was eventually buried under untold thousands of pounds of snow.
An international team of scientists has analyzed recent snow deposits in Antarctica and discovered the presence of a material that comes from outside our Solar System. They discovered samples of a particular isotope of iron, iron-60, in freshly fallen snow and they are confident that it could only have come from outside our planetary system.
The researchers suspect this rare element arrived in Antarctica in the form of interstellar dust, and it arrived in the last 20 years.
The group found far more radioactive isotopes than they would have if the dust had just passed through everyday cosmic rays en route to Earth. Rather, the team cited their past work, which showed that a supernova had deposited iron into our solar system sometime within the last 1.5 to 3 million years, Gizmodo reports. It’s likely, then, that the Earth is currently traveling the remnants of that explosion, a hunch that could help scientists better map the composition of the Milky Way.
The most abundant type of iron found is iron-56, which has 26 protons and 30 neutrons in its nucleus, and makes up almost 92 percent of all iron there is. It is one of the four stable isotopes of iron. Iron-60, which they found, has an extra four neutrons and is slightly radioactive, decaying with a half-life of 2.6 million years.
This particular radioactive element can be produced in certain nuclear processes and in supernovae. Astronomers have found it in interstellar space, but it has also been found on Earth at the bottom of the sea (dating back 2–2.5 million years) and on the Moon, suggesting that over the past few million years Earth has been showered with material from nearby supernovae, which should show up in geological formations.
One has to wonder how did the dust get there? Well, this team of researchers has previously shown that a nearby supernova deposited iron-60 in the solar system in the past 1.5 million to 3 million years, explained the study author Thomas Faestermann from TU Munich. If this iron-60-rich dust is still raining down onto Earth, then we could be passing through a dust cloud left over from this supernova.
This shows the importance of studies like these which can better paint a picture of the interstellar environment through which the Sun is traveling. Astronomers have gathered that the Sun is in the midst of a “Local Bubble,” an area where the interstellar medium is much less dense than average, perhaps because of a relatively recent supernova. Inside the bubble is the Local Interstellar Cloud, a region that’s a little denser than the Bubble. Radioactive nuclei from Antarctic snow could be an important way to probe the origins of the Bubble and Cloud.
The more we know about the timing and location of supernova explosions in our cosmic neighborhood, the better we can understand the Universe around us – and the footprints it leaves down here on Earth.
While this find is important, there is plenty more work to be done – Koll hopes to one day explore older material to see how the deposition of this dust changed over time.
The find proves that Antarctica is more than just an icy desert. It could be concealing a secret history of ancient supernovae.
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