An international team of scientists analyzing fragments of ancient meteorites recovered on Earth has made the remarkable discovery of extraterrestrial sugars vital to the formation of life.
In a study, published in the Proceedings of the National Academy of Sciences, the researchers reveal how they used gas chromatography mass spectrometry to analyze the chemical nature of powdered samples of two meteorites. The subsequent report detailed an abundance of bio-essential sugars such as arabinose, xylose and ribose; with the latter a vital component of RNA (Ribonucleic acid).
“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, Japan, said a statement. “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.”
Life finds a way
One theory for how life evolved on Earth stems from what's known as the "Late Heavy Bombardment," a period of time dating back 4.1 to 3.8 billion years ago when the inner solar system was densely packed with asteroids. As a result, a disproportionately large number of collisions took place between these wandering bodies and the terrestrial planets of Mercury, Venus, Earth and Mars. This period of bombardment was so cataclysmic, that as many as 22,000 impact craters with diameters in excess of 12 miles may have scarred Earth's young surface.
From this violent beginning, however, the seeds of life may have first been planted. Some researchers believe that RNA, which carries genetic information, evolved first on Earth and was later replaced by DNA.
“The sugar in DNA (2-deoxyribose) was not detected in any of the meteorites analyzed in this study,” added 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.”
For those wondering if the meteorite sugars may have become contaminated in their time on Earth, the researchers have an answer there as well.
"Life on Earth prefers to use the lighter variety of carbon (12C) over the heavier version (13C)," they write. "However, the carbon in the meteorite sugars was significantly enriched in the heavy 13C, beyond the amount seen in terrestrial biology, supporting the conclusion that it came from space."
Moving forward, the research teams plans on studying more meteorites to gauge the abundance of these the extraterrestrial sugars. They're also eagerly looking forward to analyzing pristine samples recently collected from primitive asteroids Ryugu and Bennu by Japanese and American spacecraft. How abundant are bio-essential sugars in the universe? We'll find out more when the samples return to Earth in late 2020 and 2023 respectively.