Scientists have reported the discovery of “the first protein from an extraterrestrial source,” marking the only time that this important component of life has ever been found in a meteorite.
Tiny traces of a novel protein called “hemolithin” were detected inside the meteorite Acfer 086, according to a study recently published on the preprint archive arXiv and spotted by Futurism. The find could have big implications for understanding the origins of life on Earth or elsewhere in the universe, though it must be corroborated by other researchers first.
“At this point, we need other scientists to employ our careful methods to repeat our results,” said study co-author Julie McGeoch, a molecular biologist at Harvard University, in an email. McGeoch’s team has submitted the study to the Proceedings of the National Academy of Sciences, but it has not yet been peer-reviewed.
Though other teams will need to confirm the results, it’s worth noting that the new detection of a “meteoritic protein,” as it is described in the study, is the culmination of more than a decade of research.
In 2007, McGeoch and her frequent collaborator Malcolm McGeoch, who is CEO of a company called PLEX that supplies the semiconductor industry, were studying interactions between water and proteins. The experiments got McGeoch thinking about possible water-protein reactions that might have occurred inside the interstellar clouds that eventually coalesced into our solar system.
These early chemical reactions and presolar ingredients are essential clues about how Earth came to host life, and how common habitable conditions might be in other star systems. Meteorites, which are space rocks that land on Earth, are godsends for scientists studying these problems because they are time capsules that often date back to the infant solar system.
Meteorites have been known to contain amino acids, organic compounds that make up proteins, for decades. But to figure out whether meteorites can contain full proteins, as opposed to just amino acids, McGeoch’s team needed to isolate potential proteins from samples, analyze their chemical makeup, and characterize their molecular structure.
This required access to “the very best mass spectrometry,” McGeoch said, which was provided by the company Bruker. With that data, the team was able to characterize a protein they call hemolithin in the Acfer 086 meteorite, which was found in Algeria in 1990.
To make sure that the protein wasn’t simply contamination from an earthly source, the researchers calculated its deuterium/hydrogen (D/H) ratio, which is a value that contextualizes the origins of materials. The results revealed “very high extraterrestrial D/H ratios,” according to the study, suggesting that the protein was formed in the proto-solar disc or perhaps even earlier, in interstellar molecular clouds that existed long before the Sun’s birth.
Given that some meteorites contain stardust grains that are older than our solar system, it is not outlandish to imagine that they could also preserve proteins that date back billions of years. Hemolithin is a particularly intriguing example because it might be able to split water into its constituent oxygen and hydrogen parts, which is a process that played a major role in the development of life on Earth.
Hemolithin’s water-splitting behavior “is only speculation at this point,” McGeoch noted. “If true, this could be a chemical energy source, which is the most important ingredient for a biochemical process leading on to life.”
To that end, McGeoch and her colleagues plan to continue testing hemolithin’s properties, while also trying to pin down the protein’s exact crystal structure. Those lines of research, combined with any confirmed detections of meteoritic proteins by other teams, will shed light on the extraordinary conditions that led to life on Earth.