Extraterrestrial sugars discovered in two meteorites that hit Earth provide vital clues to the origin of life on Earth

Scientists had previously detected other important building blocks of life, including components of proteins, DNA and RNA, in meteorites


                            Extraterrestrial sugars discovered in two meteorites that hit Earth provide vital clues to the origin of life on Earth

Scientists have found the ingredient necessary for life -- sugars -- in two different meteorites that hit Earth, according to a NASA statement. The study suggests that clashes with these celestial bodies may have laid the bedrock essential for life on ancient Earth.

One type of sugar that hitched a ride on the meteorites, ribose, is a part of RNA (ribonucleic acid). Finding ribose in the meteorites supports the idea that life on Earth sprouted from RNA, a theory backed by many scientists. Besides ribose, scientists found arabinose and xylose -- sugars found in plants and bacteria.

An artist’s concept of meteors impacting ancient Earth. Some scientists think such impacts may have delivered water and other molecules useful to emerging life on Earth. (NASA's Goddard Space Flight Center Conceptual Image Lab)

“The 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.” says Yoshihiro Furukawa of Tohoku University, Japan, lead author of the study. The findings have been published in the Proceedings of the National Academy of Sciences.

Meteorites have hosted other ingredients crucial to life before. “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,” says Furukawa.

The team arrived at their findings after analyzing two meteorites that made their way to our planet: Northwest Africa 801 and the Murchison meteorite. By analyzing powdered samples of the meteorites, they could identify individual molecules in them, NASA reports. In addition to finding sugars, they realized that the meteorites were carbon-rich, a feature that is crucial for life to begin.

This is a model of the molecular structure of ribose and an image of the Murchison meteorite. Ribose and other sugars were found in this meteorite. (Yoshihiro Furukawa)

But before they published their findings, the scientists had to rule out the possibility that the ribose could be contamination from our very own planet. After further analysis, they realized that the contamination was unlikely: the extraterrestrial ribose had significant amounts of a heavier form of carbon. In contrast, life on our planet has a preference for a lighter version of carbon, says the team.

To gain more insights into the abundance of the extraterrestrial sugars, the team will analyze more of such meteorites. “These results will help guide our analyses of pristine samples from primitive asteroids Ryugu and Bennu, to be returned by the Japan Aerospace Exploration Agency’s Hayabusa2 and NASA’s OSIRIS-REx spacecraft,” says Jason Dworkin, a co-author of the study at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

Further, these studies will also help scientists understand how these sugars are different from those present on Earth, says the statement.

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