Cosmic dust found in Antarctic snow was probably born in a distant supernova millions of years ago. The dust's interstellar journey eventually brought the material to Earth, where scientists discovered the ancient grains.
This pond stood out because it contains an iron isotope called iron-60, which is often released by supernovae but very rare on Earth. (Isotopes are versions of elements that differ in the number of neutrons in their atoms.)
In the search for difficult-to-capture space dust, researchers analyzed more than 1100 kg. (500 kg) of surface snow which they collected from an altar region in Antarctica near the German Kohnen Station. At that location, the snow would be mostly free of pollution from ground dust, the researchers reported in a new study.
The investigators then sent the still frozen snow to a laboratory in Munich, where it was melted and filtered to isolate dust particles that may contain traces of material from space. When researchers investigated the burnt dust using an accelerator mass spectrometer, they discovered the rare isotope Iron-60 ̵
Space is a dusty place, rich with particles expelled by supernovae and hidden from planets, asteroids and comets. Our solar system is currently passing through a large cloud of space dust called the Local Interstellar Cloud (LIC), and grains from this cloud found on Earth can reveal much about how our sun and its planets interact with cosmic dust.
to find out if the spacecraft came from a distant supernova, scientists must first rule out if it originated from our solar system. Irradiated dust thrown by planets and other bodies may hold iron-60, but exposure to cosmic radiation also creates another isotope: manganese-53. The researchers compared iron-60 to manganese-53 ratios in the Antarctic grains and found that the amount of manganese was much lower than it would have been if the dust were local.
How did the scientists know that iron-60 in Antarctica does not have snow on Earth? There may have been iron-60 on our planet during its infancy, but all of this rare isotope has long since expired on Earth, the researchers wrote in the study. Nuclear bomb tests could have created and spread iron-60 across the planet, but calculations showed that the amount of isotope produced by such tests would have been much lower than the amount of iron-60 found in Antarctic snow.
Iron 60 is also produced in nuclear reactors; however, the amount of isotope that reactors generate is "insignificant" and is limited to the reactors where it is manufactured, the researchers said. So far, even serious nuclear accidents, such as the Fukushima Daiichi nuclear power plant disaster in 2011, have not introduced iron-60 to the environment in measurable amounts, according to the study.
Earlier, iron-60 on earth has been found only in ancient deep-sea deposits or in rocks that originate in space, "like meteorites or on the moon," researchers reported online August 12 in the journal Physical Review Letters.
"By excluding terrestrial and cosmogenic sources [shaped by cosmic rays]we conclude that for the first time we have recently found iron-60s of interstellar origin in Antarctica," the researchers wrote.
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Originally published on Live Science .
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