Life’s ingredients are readily available on asteroids

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New Delhi: Scientists have carefully examined the rock and dust returned from the asteroid Bennu by NASA’s OSIRIS-REx mission in September 2023, and discovered ribose a sugar necessary for making ribonucleic acid (RNA), along with glucose for the first time in an extra-terrestrial sample. Glucose is a source of energy for life on Earth. Ribose has previously been discovered in meteorites on Earth, so it is not surprising, but what is surprising is the lack of detection of deoxyribose, necessary for making deoxyribonucleic acid (DNA). The research provides strong evidence in support of the RNA World hypothesis, which suggests that primordial life was RNA dominated in the absence of proteins.

Graphic labeled "Bio-essential sugars ribose and glucose in samples from asteroid Bennu." The left half of the graphic has a background image of Bennu. In front of it are the RNA molecular components on Bennu: guanine, cytosine, ribose, adenine, uracil, and phosphate. Below them, the molecular structure of glucose is accompanied by text: "Ribose and glucose are sugars essential to life on Earth. RNA uses ribose for its structure. Glucose provides cells with energy and is used to make fibers like cellulose. A team of Japanese and US scientists have found ribose and glucose in samples of asteroid Bennu (collected by NASA'S OSIRIS-REx mission), suggesting that these simple sugars were brought to the early Earth by meteorites." The right half of the graphic has a background image of Earth. In front of it is the genetic code for protein synthesis, including ribose, phosphate, and the RNA nucleobases guanine, cytosine adenine, and uracil. Below that, the chemical process of energy production via glycolysis and the chemical structure of cellulose are annotated.

The discovery of bio-essential sugars on Bennu. (Image Credit: NASA/Goddard/University of Arizona/Dan Gallagher).

One of the leading theories for the emergence of life is that the first life forms relied on RNA to store information and drive chemical reactions necessary for life. While for most life on Earth today, DNA is the primary carrier of genetic information in cells, with RNA performing a number of functions essential to life. RNA can catalyse biochemical reactions, and itself carry genetic information. In laboratory conditions, RNA has replicated on its own. The lack of detection of deoxyribose in the Bennu samples indicates that ribose may have been more common than deoxyribose on terrestrial surfaces in the infancy of the Solar System.

A water world battered to bits

A paper describing the findings has been published in Nature Geoscience. Initial analysis itself had revealed that the samples contained carbon, organic molecules and phosphate along with water. The remarkable discoveries are shaking up theories of life on Earth, and indicate that Bennu may have hosted liquid water on its surface in the distant past, and was subsequently battered to bits in the chaotic infancy of the Solar System.