The cosmic dust found in the Antarctic snow was probably born in a supernova millions of years ago. The interstellar journey of the dust eventually brought the material to Earth, where scientists discovered ancient grains.
This powder stood out because it contains an iron isotope called iron-60, which is commonly released from supernovas but very rare on Earth. (Isotopes are versions of elements that differ in the number of neutrons in their atoms.)
In the search for elusive space dust, the scientists analyzed over 1,100 pounds. (500 kilograms) of surface snow that they collected from a high-altitude region of Antarctica near the German Kohnen station. In that position, the snow would be mostly free of ground dust contamination, the researchers reported in a new study.
Investigators then sent the frozen snow to a laboratory in Munich, where it was melted and filtered to isolate dust particles that could contain traces of material from space. When the scientists examined the incinerated powder using an accelerator mass spectrometer, they discovered the rare iron-60 isotope, a relic of an ancient supernova.
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Space is a dusty place, rich in particles expelled by supernova and scattered by planets, asteroids and comets. Our solar system is currently going through a big cloud of space dust known as Local Interstellar Cloud (LIC), and the grains of this cloud found on Earth could reveal a lot about how our sun and its planets interact with cosmic dust.
To find out if the space dust came from a distant supernova, scientists had to first rule out if it came from our solar system. The irradiated powder released by the planets and other bodies may contain iron-60, but exposure to cosmic radiation also creates another isotope: manganese-53. The researchers compared the ratios of iron-60 and manganese-53 in Antarctic grains, discovering that the amount of manganese was much lower than it would have been if the powder were local.
How did scientists know that 60-iron in Antarctic snow did not originate on Earth? There may have been 60 iron on our planet during his childhood, but all this rare isotope has long since fallen on Earth, the researchers wrote in the study. Nuclear bomb tests he could have created and dispersed 60-iron all over the planet, but the calculations showed that the amount of isotope produced by such tests would have been much lower than the amount of iron-60 found in the snow of the Antarctica.
Iron-60 is also produced in nuclear reactors; however, the amount of isotope that the reactors generate is "insignificant" and is limited to the reactors in which it is produced, the scientists said. To date, even serious nuclear accidents, such as the Fukushima Daiichi nuclear power plant disaster in 2011, it did not introduce iron-60 in the environment in measurable quantities, according to the study.
Previously, 60 iron on Earth had been found only in ancient deep-water deposits or in rocks originating in space, "like meteorites or on the moon," the scientists reported online on August 12 in the journal Letters of physical revision.
"Excluding terrestrial and cosmogenic sources (modeled by cosmic rays), we conclude that we have found, for the first time, the recent 60-iron with interstellar origin in Antarctica," the researchers wrote.
Originally published on Live science.