An international team of researchers has discovered molecules of sugar in meteorites for the first time. No, candy is not raining down on Earth in the form of delicious space rocks, but the discovery is still pretty important: The sugar discovered is essential for life.
As reported in the Proceedings of the National Academy of Sciences, the team identified the presence of bio-essential sugars including ribose, arabinose, and xylose in two carbon-rich meteorites known as NWA 801 and Murchinson. Forms of ribose, in particular, make up the backbone of RNA, and variations are the fundamental structures of DNA. This discovery adds to the already substantial list of biologically important molecules found in meteorites, lending evidence to the theory meteorites bombarding our planet may have contributed towards kick-starting life on Earth.
“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,” lead author Yoshihiro Furukawa of Tohoku University said in a statement.
“This research provides the first direct evidence of ribose in space and the delivery of the sugar to Earth. The extraterrestrial sugar might have contributed to the formation of RNA on the prebiotic Earth, which possibly led to the origin of life.”
The two samples have characteristics that make them very unlikely to have formed on Earth, though the researchers do concede that they have to consider the possibility the samples have been contaminated by terrestrial life. But, as they point out, we have two pristine samples of asteroid material on our way to us over the next few years to check: one from asteroid Ryugu and the other from asteroid Bennu. Lessons learned analyzing the sugary meteorites here will be crucial in the study of such future samples.
The analysis showed the abundance of ribose and the other sugars to be between 2.3 and 11 parts per billion in NWA 801 and 6.7 to 180 parts per billion in Murchison. The values are small but if we consider the number of impacts our planet received in the first billion years of its existence, a large number of organics were brought down from outer space, and that could be how life started.
“The sugar in DNA (2-deoxyribose) was not detected in any of the meteorites analyzed in this study,” said Danny Glavin, a co-author of the study at NASA Goddard. “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.”
The team plans to look at many more meteorites to get a better idea of the abundance of extraterrestrial sugar as well as more details about their properties. This might provide new clues on how organics form in space and possible insights into how life forms from non-biological chemical processes.