How does one acquire star dust? One option, as the Perry Como song suggests, is to catch a falling star and put it in your pocket, so to speak: thousands of tonnes of cosmic dust bombard the Earth each year, mostly vaporising in the atmosphere.
The asteroid and comet fragments that don’t burn up – known as meteorites and micrometeorites if they hit Earth – provide scientists with valuable clues about the cosmos. It’s why planetary scientists in the UK, kitted in ghostbusters-like vacuum backpacks, have scoured cathedral roofs for microscopic specks of the space stuff.
Another option is to recreate a bit of the universe in a bottle.
Linda Losurdo, a PhD candidate in materials and plasma physics at the University of Sydney, has done exactly that, producing cosmic dust in the lab from scratch. It’s a feat she hopes will help shed new light on how life began on Earth.
Cosmic dust is thought to originate from dying stars. A star at the end of its life gets “very hot and heavy around the outer part”, Losurdo said. Breaking apart under its own pressure, it “start[s] to belch out … huge waves of carbon”.
“What is found around the envelopes of giant, dying stars [is] quite similar to what is found in meteorites,” Losurdo said.
Cosmic dust contains organic compounds of carbon, hydrogen, oxygen and nitrogen – known collectively as CHON molecules, which form the chemical building blocks of life.
Astrophysicist Dr Sara Webb described Losurdo’s work as ‘a really beautiful method’ to produce something similar to ‘what we think interstellar dust is like’. Photograph: University of Sydney
Scientists still debate whether the earliest CHON molecules formed locally on Earth, arrived later as particles from comets and asteroids, or were delivered during the early stages of our solar system forming – or some combination of the three.
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Recreating cosmic dust in the lab may help answer questions about how meteorites hitting Earth came to contain the organic matter that they do, Losurdo said. “We’re really interested in how we can better predict where the types of dust that we find in meteorite samples came from.”
Cosmic dust emits a distinctive infrared fingerprint, a unique pattern of light that reveals its chemical structure.
In the lab, Losurdo used such patterns to reverse-engineer the dust, first using a vacuum to recreate the near-empty conditions of space in a glass tube.
To the tube, she and her supervisor, Prof David McKenzie of the University of Sydney, introduced a mixture of nitrogen, carbon dioxide and acetylene gas – “the types of gases that you would find around giant dying stars”.
“We’re then able to apply a very high voltage – around 10,000 volts – and … it energises the gas,” Losurdo said – creating a type of plasma, the fourth state of matter. “That is our dust analogue.”
Dr Sara Webb, an astrophysicist at Swinburne University who was not involved in the research, said: “All of these types of dust particles were the building blocks for our life here on Earth. We wouldn’t be here without them.”
“We know that they exist out there in the universe, all scattered throughout the place, but we obviously can’t go and grab a bit of the dust from the interstellar medium, even though we would love to.”
Webb described Losurdo’s work as “a really beautiful method” to produce something similar to “what we think interstellar dust is like”.
“One very exciting possibility, which is probably further down the track is … to use this kind of simulated cosmic dust in other organic chemistry experiments, to simulate early life formation on different types of planets,” Webb said.
Losurdo emphasised that “what we’re making is not representative of every single environment in the universe”.
“What we’re trying to do is to take a snapshot of something that is physically plausible and see if what we make compares to the real thing.”
The research was published in the Astrophysical Journal of the American Astronomical Society.
