A Sydney PhD student has created cosmic dust from scratch by recreating a small part of the universe inside a laboratory bottle. The experiment provides new clues about how some of the chemical components associated with life developed before Earth formed.
Linda Rosrud, a PhD candidate in materials physics and plasma physics in the School of Physics, combined nitrogen, carbon dioxide, and acetylene to simulate the energy states found near stars and supernova remnants.
She then exposed the gas to a strong electric charge. This process produced carbon-rich dust similar to the material that floats through interstellar space and is stored inside comets, asteroids, and meteorites.
The survey results are Astrophysical Journal of the American Astronomical Society.
Cosmic dust containing essential elements of life
Laboratory dust contains a complex combination of carbon, hydrogen, oxygen, and nitrogen. Together, these are known as CHON molecules and are found in many organic substances considered important to life.
“We no longer have to wait for asteroids and comets to come to Earth to understand their history,” Rosrud said. “We can build an analog environment in the lab and reverse engineer its structure using infrared fingerprints.
“This could give great insight into how ‘carbonaceous cosmic dust’ forms in the plasma spewed out by giant old stars and in the cosmic nurseries of nascent stars, distributing these fascinating molecules that may be essential for life.”
“It’s like recreating a piece of the universe in a bottle in our lab.”
In space, space dust occurs under extreme conditions. Molecules can be repeatedly bombarded with ions and electrons, causing chemical reactions to create increasingly complex materials.
Astronomers identify different types of space dust by studying the infrared light it emits. These signals act like molecular fingerprints, allowing researchers to determine the chemical structure of the material.
Los Rudo’s laboratory samples produced the same distinctive infrared signature seen in space. This agreement shows that the experiment closely replicates the processes thought to occur in a real space environment.
Tracing the origins of life’s components
How life began on Earth remains one of science’s biggest unanswered questions. Researchers continue to investigate whether the first organic molecules formed on young planets, arrived on comets or meteorites, were delivered while the solar system was still forming, or a combination of these possibilities.
From about 4.56 billion years ago to 3.5 billion years ago, meteorites, micrometeorites, and interplanetary dust particles from asteroids and comets repeatedly impacted the Earth. Scientists believe that these objects carried vast amounts of organic material to the surface.
However, it remains unclear where the substance originally formed and what process it was produced.
“Covalently bonded carbon and hydrogen in comet and asteroid material are thought to have formed in the outer shells of stars, in high-energy events such as supernovae, and in interstellar environments,” Rosrud said.
“What we are trying to understand are the specific chemical pathways and conditions that incorporate all the CHON elements into the complex organic structures found in cosmic dust and meteorites.”
Reproducing the space inside a glass tube
Rosrud conducted the experiment with his supervisor, Professor David McKenzie. The researchers first used a vacuum pump to remove air from the glass tube, creating a nearly empty space.
The tube was then filled with nitrogen, carbon dioxide, and acetylene. For about an hour, the gas mixture was exposed to a potential of about 10,000 volts. This created a type of plasma called a glow discharge.
The intense energy splits the original molecules. Those components then recombine into larger, more complex chemical structures.
Over time, the newly formed material settled onto the silicon chip placed inside the tube, leaving behind a thin coating of dust. In some samples, the particles collected resembled glowing debris of cosmic matter.
McKenzie, a co-author of the study, said the dust on Earth gives scientists access to conditions that are difficult to examine directly in space.
“By creating cosmic dust in the lab, we can study the strength of ion bombardment and the temperature at which dust forms in space,” Professor McKenzie said. “This is important if we want to understand the environment inside cosmic dust clouds, where life-related chemistry is thought to occur.
“This can also help us interpret what processes meteorites and asteroid fragments have undergone over their lifetimes. Their chemical signatures contain records of those processes, and experiments like this help us learn how to read those records.”
Building a fingerprint library for astronomers
This research could do more than reveal how molecules associated with life were first formed. The research team also plans to build a detailed database of infrared fingerprints produced by different types of space dust created in the laboratory.
Astronomers were able to compare those signatures with observations of star-forming regions and the remains of dead stars. If the signals match, it could reveal where specific forms of dust are produced and help researchers reconstruct the physical and chemical processes that occur there.
The database could also improve scientists’ ability to interpret the history recorded inside meteorite and asteroid debris. Their chemistry allows them to preserve evidence of the effects of temperature, radiation, and particles they experienced while traveling through space.
This study provides researchers with a new way to investigate processes occurring deep within stellar environments by recreating cosmochemistry in the laboratory. It may also reveal some of the ancient chemical processes that ultimately contributed to the emergence of life on Earth.
Rosrud won the best presentation award for this research at the International Annual Meeting of the Meteorite Society late last year.
The authors reported no competing interests. They acknowledge support from the University of Sydney Node of Microscopy Australia and this research received funding from the Australian Research Council.
