Losurdo and her supervisor, Professor David McKenzie, filled evacuated glass tubes with nitrogen, carbon dioxide and acetylene before applying around 10,000 volts of electrical potential for about an hour. The resulting glow discharge plasma broke apart the gas molecules and drove them to recombine into new structures. Over time, these products condensed onto silicon chips inside the tubes as a thin layer of carbon rich dust.

Analysis showed that this laboratory dust contains a mixture of carbon, hydrogen, oxygen and nitrogen, the CHON elements that underpin many organic compounds associated with life. Infrared measurements revealed distinctive spectral fingerprints that match the signatures astronomers see from carbonaceous dust in interstellar space, comets, asteroids and meteorites. This close agreement indicates that the plasma process in the lab is a realistic analogue for dust formation in extreme astrophysical environments.

Cosmic dust grains form in the outer envelopes of giant, old stars, in explosive events such as supernovae, and in diffuse interstellar regions where gas and radiation constantly interact. In space, these particles are continuously bombarded by ions and electrons, which modify their structure while preserving a record of their history in their chemical bonds. The new study shows that those conditions can be recreated on Earth and studied under controlled parameters.

Losurdo explained that researchers no longer need to wait for meteorites or cometary samples to arrive on Earth to investigate such dust. By building analogue environments in the lab and reading their infrared fingerprints, scientists can infer how carbonaceous material forms and evolves as it circulates through stellar nurseries and debris clouds. This helps illuminate how life relevant chemistry operates inside cosmic dust clouds.

The work also relates directly to long standing questions about the origin of organic material on the early Earth. Between about 3.5 and 4.56 billion years ago, the planet was heavily bombarded by meteorites, micrometeorites and interplanetary dust particles derived from asteroids and comets. These impactors likely delivered large amounts of carbon rich material to the surface, but the precise steps that produced those molecules in space remain uncertain.

By comparing dust created under different ion bombardment intensities and temperatures, the Sydney team can distinguish the roles these factors play in building complex carbonaceous structures. Professor McKenzie said that making cosmic dust in the lab allows scientists to explore ranges of ion impact and thermal conditions that are impossible to probe directly in space. Understanding these regimes is essential for interpreting the chemical records preserved in meteorites and asteroid fragments.

Each dust grain carries a history of the environments it has passed through, encoded in its molecular structure and bonding. Experiments like this provide a way to calibrate that record, linking specific infrared features to particular formation pathways and processing histories. In turn, astronomers can use those calibrated fingerprints to identify promising regions of space for life relevant chemistry when they observe stellar nurseries or the remnants of dead stars.

The researchers plan to build a comprehensive database of infrared spectra from their lab made dust analogues. Such a library would allow observers to match astronomical data with specific dust recipes and plasma conditions, effectively letting them reverse engineer distant environments from their light. This approach could reveal where CHON rich grains are most abundant and how they are transformed as they move from stellar envelopes into interstellar clouds and planetary systems.

Beyond tracing the journey of dust, the work opens a window onto the earliest steps that may have led to life on Earth. If complex organic structures can form efficiently in plasma environments around stars and within interstellar clouds, then planetary systems may inherit a rich supply of prebiotic material from the outset. The Sydney experiments demonstrate that this chemistry is not only plausible but accessible to detailed laboratory study.

Losurdo received a best presentation award at the Annual Meeting of the Meteoritical Society for this research, highlighting its importance to the study of meteorites and cosmic dust. The work was supported by the Australian Research Council, and the team acknowledged assistance from the University of Sydney node of Microscopy Australia, which enabled detailed examination of the dust particles and their glittering, cosmic like appearance on the chips.

Research Report:Carbonaceous cosmic dust analogues distinguish between ion bombardment and temperature

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