Using simple gases and electricity in a lab setup that mimicked a stellar neighborhood, Linda Losurdo, a doctoral student in materials and plasma physics at the University of Sydney, created a tiny amount of cosmic dust. It is the same substance that clumps to form stars, and acts as a catalyst for organic compounds that could have been the simplest predecessors of molecules that built life.
Cosmic dust is abundant in the vast space between stars, known as interstellar space, and is even embedded in comets and asteroids. Despite being bombarded by particles and rocks, very little of the cosmic dust remains. Most of it burns up due to friction in the atmosphere, and the negligible amount that remains in the meteorites is impossible to locate and collect.
“When we’re looking at big questions like the origins of life, we have to look at where the building blocks started from,” Losurdo said. “Where did all the carbon on Earth begin its life, and what type of journey did it have to go through in order to then be able to build into things like amino acids?”
Amino acids were one of the first molecules to appear on Earth, and are the building blocks of proteins, which themselves are part of almost every life process. Using lab-made cosmic dust, scientists can understand whether amino acids originated on Earth or in space.
Cosmic dust analogues can help scientists study the vital chemistry that led to life on Earth without requiring samples from space. Even a small amount of this substance can give a lot more information than anything collected from meteorites, since there’s very little that they have to offer. Collecting dust from a giant, dying old star is a pipe dream.
To produce cosmic dust, Losurdo evacuated a glass tube and introduced nitrogen, carbon dioxide, and acetylene—a colorless, odorless gas used in a welding torch —into it. Acetylene consists of carbon and hydrogen. With coauthor David McKenzie, a professor of materials physics at the University of Sydney, she applied 10,000V of electricity to the gases for an hour, making a type of plasma, or electrically charged gas, known as “glow discharge”.
Since the electricity travels inside the gas, a circuit forms and electrons fly off from the excited gas molecules. In these conditions, the materials want to bind and coalesce to form clumps. It’s one of the most common and natural processes that takes place around stars.
Losurdo produced about a gram of cosmic dust in total. Since cosmic dust is difficult to collect and analyze, she deposited it on a silicon wafer. This artificial dust is analogous to cosmic dust in its original form, not affected by chemical processes that occur after it becomes embedded in meteorites and comets, or by processes that catalyze the formation of organic molecules.
Losurdo cannot mimic the exact conditions in space; she can only do so much to re-create the complexity of the natural process. She aims to move closer to the range of conditions observed in a new nebula, a supernova remnant, or the envelope of a giant star.
The next step is to create a database of cosmic dust prepared under different conditions and observe the changes in its composition. Losurdo plans to bring the cosmic dust closer to the real thing, so that it can be ‘matched’ to objects like meteorites. Since the dust obtained is in a pristine state, scientists can study its evolution.
Chemical complexity had simple beginnings when hydrogen, carbon monoxide, water, and other small molecules were deposited on dust grains, a process that will be exciting to investigate in laboratories. Recreating an analogue in controlled conditions can be applied to understand the natural world. The results support the hypothesis that raw materials that contribute to life are shaped by the energetic environments in which they form. Instead of treating them as mere chemical signatures, scientists can reconstruct the history of organic compounds found in asteroids, comets, and interstellar dust.
The results can bridge the gap between telescopic observations and laboratory analyses, providing a starting point for testing how organic matter evolves in space. It suggests that organic compounds form readily in stellar environments, and essential building blocks of life are spread across planetary systems throughout the galaxy.
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