Who are we? Why do we exist? As the song by Crosby, Stills, Nash & Young indicates, we are made from stardust, formed through chemical processes in extensive clouds of interstellar gas and dust. To delve deeper into how this chemistry might lead to prebiotic molecules—the building blocks of life on Earth and potentially beyond—researchers have looked into the effects of low-energy electrons generated when cosmic radiation passes through ice particles. Their discoveries could also have implications for medical and environmental applications on our planet.
Who are we? Why do we exist? As the classic song by Crosby, Stills, Nash & Young suggests, we are made from stardust, a product of chemical reactions that unfold in massive clouds of interstellar gas and dust. To further investigate how this chemistry could lead to the development of prebiotic molecules that might seed life on Earth—and perhaps elsewhere—researchers explored the significance of low-energy electrons produced by cosmic radiation interacting with ice particles. Their findings could also provide insights for medical and environmental initiatives on Earth.
Undergraduate student Kennedy Barnes will showcase the team’s findings at the upcoming fall meeting of the American Chemical Society (ACS).
“The initial discovery of molecules in space was accomplished by Wellesley College alum Annie Jump Cannon over a century ago,” states Barnes, who, along with fellow undergraduate Rong Wu, conducted this research under the guidance of chemistry professor Christopher Arumainayagam and physics professor James Battat. Since Cannon’s groundbreaking work, scientists have been eager to learn how extraterrestrial molecules come into being. “Our objective is to examine how significant low-energy electrons are compared to photons in triggering the chemical reactions linked to the extraterrestrial formation of these prebiotic molecules,” explains Barnes.
Previous studies that addressed this topic indicated that both electrons and photons could drive the same reactions. However, the research conducted by Barnes and her team suggests that the yield of prebiotic molecules from low-energy electrons and photons may differ significantly in the cosmos. “Our calculations reveal that the amount of electrons induced by cosmic rays in cosmic ice could greatly exceed the number of photons hitting the ice,” reveals Barnes. “Thus, it appears that electrons may play a more crucial role than photons in the extraterrestrial formation of prebiotic molecules.”
Beyond cosmic ice, her work on low-energy electrons and radiation chemistry holds promise for applications on Earth. Barnes and her colleagues recently examined the radiolysis of water, discovering evidence that low-energy electron stimulation can lead to the release of hydrogen peroxide and hydroperoxyl radicals, both of which can deplete stratospheric ozone and contribute to harmful oxidative stress in human cells.
“Many of our findings related to water radiolysis could be utilized in medical contexts and simulations,” Barnes shares, noting the potential for high-energy radiation to play a role in cancer treatment. “I once heard a biochemistry professor remark that humans are essentially composed of water. Therefore, other scientists are investigating the impact of low-energy electrons generated in water on DNA molecules.”
She also mentions that the team’s results are relevant for environmental cleanup strategies where wastewater undergoes treatment using high-energy radiation, resulting in a substantial generation of low-energy electrons believed to be instrumental in degrading hazardous substances.
In efforts to enhance understanding of how prebiotic molecules form, the researchers extended their investigations beyond theoretical models and recreated space-like conditions in the laboratory. They utilized an ultra-high vacuum chamber with an extremely pure copper substrate that can be cooled to very low temperatures, alongside an electron gun to produce low-energy electrons and a plasma lamp driven by lasers to generate low-energy photons. By bombarding nanoscale ice films with these particles, the scientists analyzed the resulting molecular formations.
“While we previously centered our focus on the implications for interstellar submicron ice particles, our work also pertains to larger cosmic ices, such as those found on Jupiter’s moon Europa that has a thick ice shell spanning 20 miles,” Barnes notes.
Consequently, she believes their research will aid astronomers in interpreting data from space missions like NASA’s James Webb Space Telescope as well as the upcoming Europa Clipper, which is expected to launch in October 2024. Barnes is hopeful that their discoveries will motivate other researchers to integrate low-energy electrons into their astrochemical models simulating processes within cosmic ices.
The team is also experimenting with different molecular compositions of ice films and investigating how low-energy electrons might facilitate other prebiotic chemical reactions. This collaborative work is being conducted with experts from the Laboratory for the Study of Radiation and Matter in Astrophysics and Atmospheres in France.
“There’s an incredible amount that we are on the verge of uncovering, which I find incredibly exciting,” says Barnes, characterizing this as a new era in space exploration.
The research received funding from the U.S. National Science Foundation, the Arnold and Mabel Beckman Foundation, Wellesley College Faculty Awards, Brachman Hoffman grants, and the Nancy Harrison Kolodny ’64 Professorship.
