A PhD student in Sydney has produced cosmic dust from scratch by recreating a small piece of the universe inside a laboratory bottle. The experiment offers new clues about how some of the chemical ingredients associated with life could have developed before Earth even formed.
Linda Losurdo, a PhD candidate in materials and plasma physics in the School of Physics, combined nitrogen, carbon dioxide and acetylene to simulate the energetic conditions found near stars and supernova remnants.
She then exposed the gases to a powerful electrical charge. The process created carbon-rich dust resembling material that floats through interstellar space and is preserved inside comets, asteroids and meteorites.
The findings were published in The Astrophysical Journal of the American Astronomical Society.
Cosmic Dust With Life’s Essential Elements
The laboratory dust contains complex combinations of carbon, hydrogen, oxygen and nitrogen. Together, these are known as CHON molecules and are found in many organic substances considered important for life.
“We no longer have to wait for an asteroid or comet to come to Earth to understand their histories,” Ms. Losurdo said. “You can build analogue environments in the laboratory and reverse engineer their structure using the infrared fingerprints.
“This can give us huge insight into how ‘carbonaceous cosmic dust’ can form in the plasma puffed out by giant, old stars or in cosmic nurseries where stars are being born and distribute these fascinating molecules that could be vital for life.
“It’s like we have recreated a little bit of the Universe in a bottle in our lab.”
In space, cosmic dust develops under extreme conditions. Molecules are repeatedly struck by ions and electrons, triggering chemical reactions that can create increasingly complex materials.
Astronomers identify different types of cosmic dust by studying the infrared light they emit. These signals act like molecular fingerprints, allowing researchers to determine the chemical structure of the material.
Losurdo’s laboratory samples produced the same distinctive infrared signatures seen in space. That match indicates that the experiment closely reproduces the processes believed to occur in real cosmic environments.
Tracing the Origins of Life’s Building Blocks
How life began on Earth remains one of science’s greatest unanswered questions. Researchers continue to investigate whether the first organic molecules formed on the young planet, arrived aboard comets and meteorites, were delivered while the solar system was still taking shape, or resulted from a combination of these possibilities.
From about 4.56 billion to 3.5 billion years ago, meteorites, micrometeorites and interplanetary dust particles from asteroids and comets repeatedly struck Earth. Scientists believe these objects carried enormous quantities of organic material to the surface.
However, where that material originally formed and which processes created it are still uncertain.
“Covalently bonded carbon and hydrogen in comet and asteroid material are believed to have formed in the outer envelopes of stars, in high-energy events like supernovae, and in interstellar environments,” Ms. Losurdo said.
“What we’re trying to understand are the specific chemical pathways and conditions that incorporate all of the CHON elements into the complex organic structures we see in cosmic dust and meteorites.”
Recreating Space Inside Glass Tubes
Losurdo conducted the experiment with her supervisor, Professor David McKenzie. The researchers first used a vacuum pump to remove air from glass tubes, producing conditions that approximated the near emptiness of space.
They then filled the tubes with nitrogen, carbon dioxide and acetylene. For approximately one hour, the gas mixture was subjected to an electrical potential of around 10,000 volts. This created a form of plasma called a glow discharge.
The intense energy split the original molecules apart. Their components then recombined into larger and more complicated chemical structures.
Over time, the newly formed material settled onto silicon chips placed inside the tubes, leaving behind a thin coating of dust. In some samples, the collected particles resembled sparkling fragments of cosmic material.
McKenzie, a coauthor of the study, said producing this dust on Earth gives scientists access to conditions that cannot easily be examined directly in space.
“By making cosmic dust in the lab, we can explore the intensity of ion impacts and temperatures involved when dust forms in space,” Professor McKenzie said. “That’s important if you want to understand the environments inside cosmic dust clouds, where life-relevant chemistry is thought to be happening.
“This also helps us interpret what a meteorite or asteroid fragment has been through over its lifetime. Its chemical signature holds a record of its journey, and experiments like this help us learn how to read that record.”
Building a Fingerprint Library for Astronomers
The research could do more than clarify how life related molecules first formed. The team also plans to assemble a detailed database of infrared fingerprints produced by different types of laboratory made cosmic dust.
Astronomers could compare those signatures with observations of star forming regions and the remains of dead stars. A matching signal might reveal where certain forms of dust are being produced and help researchers reconstruct the physical and chemical processes occurring there.
The database could also improve scientists’ ability to interpret the history recorded inside meteorites and asteroid fragments. Their chemistry can preserve evidence of the temperatures, radiation and particle impacts they experienced during their journeys through space.
By reproducing cosmic chemistry in the laboratory, the study gives researchers a new way to investigate processes occurring deep within stellar environments. It may also illuminate some of the ancient chemical steps that eventually contributed to the emergence of life on Earth.
Losurdo received the award for best presentation for this research at the international Annual Meeting of the Meteoritical Society late last year.
The authors reported no competing interests. They acknowledged support from the University of Sydney node of Microscopy Australia, and the work received funding from the Australian Research Council.