Scientists found three bio-essential sugars, including ribosome, in samples from a pair of meteorites. Photo by Yoshihiro Furukawa
By Brooks Hays
For the first time, scientists have identified sugars essential to life inside meteorites.
The discovery, described this week in the journal PNAS, supports the theory that a bombardment of meteorites provided ancient Earth with the building blocks required for the origin of life.
An international team of scientists identified a trio of bio-essential sugars, including ribose, arabinose and xylose, inside two carbon-rich meteorites.
“Ribose is an essential sugar for present life as a building block of RNA, which could have both stored information and catalyzed reactions in primitive life on Earth,” researchers wrote in their new paper.
Scientists have previously found other biomolecules in meteorites, including amino acids, which form proteins, and nucleobases, the building blocks of DNA and RNA. But until now, scientists hadn’t been able to find sugars.
“The research provides the first direct evidence of ribose in space and the delivery of the sugar to Earth,” Yoshihiro Furukawa, researcher at Tohoku University in Japan, said in news release. “The extraterrestrial sugar might have contributed to the formation of RNA on the prebiotic Earth which possibly led to the origin of life.”
To find the sugars, scientists used gas chromatography mass spectrometry to analyze the chemical components of powdered meteorite samples. The method identifies molecules by measuring their mass and electric charge.
The research team used isotopic analysis to confirm the sugar’s interplanetary origins. Their tests showed a higher concentration of carbon 13 in the sugars. Carbon 13 is a heavier carbon isotope that is less abundant in terrestrial samples.
While planetary scientists continue to search for signs of life on other planets, researchers are still trying to figure out how biology — or the first living organisms — emerged from non-biological chemical processes here on Earth.
While some scientists theorize that RNA and DNA evolved together, or emerged simultaneously, others estimate that RNA came first and evolved DNA. RNA can catalyze chemical reactions, as well as make copies of itself, something DNA can’t do. Some research suggests metabolism preceded both RNA and DNA.
The latest discovery supports the theory that RNA was the initial conductor of life’s assembly.
“The sugar in DNA, 2-deoxyribose, was not detected in any of the meteorites analyzed in this study,” said study co-author Danny Glavin, researcher at NASA’s Goddard Space Flight Center. “This is important since there could have been a delivery bias of extraterrestrial ribose to the early Earth which is consistent with the hypothesis that RNA evolved first.”
Scientists hope to gain additional insights into life’s origins as they probe other meteorite samples for evidence of sugar’s abundance.