BY ROSIE MCCALL
Sugars crucial to the evolution of life on Earth have been found in meteor samples for the first time.
The discovery adds more weight to the hypothesis a meteor blitz on ancient Earth could have kick-started life by providing the necessary building blocks.
“Other important building blocks of life have been found in meteorites previously, including amino acids (components of proteins) and nucleobases (components of DNA and RNA), but sugars have been a missing piece among the major building blocks of life,” Yoshihiro Furukawa of Tohoku University, Japan, said in a statement.
A study published in Proceedings of the National Academy of Sciences of the United States of America (PNAS) sheds new light on the question of how biology arose from non-biological chemical processes, the researchers say. This being because the sugars discovered on the meteors studied may have been a key ingredient in some of the first examples of ribonucleic acid (RNA) formed on Earth.
Researchers were able to identify sugars on two carbon-rich meteorites (Murchison and North West Africa (NWA) 801) using gas chromatography mass spectrometry, a process that sorts molecules according to mass and electric charge.
Murchison fell to Earth and landed in Australia in 1969, while NWA 801 fell to Earth and landed in Northwest Africa in 2001.
“The research provides the first direct evidence of ribose in space and the delivery of the sugar to Earth,” said Furukawa, lead author of the study. “The extraterrestrial sugar might have contributed to the formation of RNA on the prebiotic Earth which possibly led to the origin of life.”
Analysis of powdered meteor samples showed levels of ribose (a critical ingredient in RNA) and other types of sugars, (including arabinose and xylose) varied—with a high of 6.7 to 180 parts per billion in Murchison and a low of 2.3 to 11 parts per billion in NWA 801.
“It is remarkable that a molecule as fragile as ribose could be detected in such ancient material,” said co-author Jason Dworkin, Deputy Director of NASA’s Solar System Exploration Division.
In contrast, there was no evidence of 2-deoxyribose—the sugar required to make DNA—in any of the samples studied, a result the researchers say supports the idea RNA evolved prior to, and was later replaced by, DNA.
“The sugar in DNA (2-deoxyribose) was not detected in any of the meteorites analyzed in this study,” said Danny Glavin, Associate Director for Strategic Science at NASA’s Solar System Exploration Division.
“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.”
Next up, the team plans to study the chemical composition of more meteorites. This, they hope, will enable them to gain a better idea of how common and how variable extraterrestrial sugars are.
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Fuente: / Source: www.newsweek.com