Life’s ‘building blocks’ in asteroid Bennu

By Sage Rohrbach

A mosaic image of the Bennu Asteriod, created using pictures from NASA’s OSIRIS-REx satellite that was near the asteroid for over two years. **Courtesy of NASA via Wikimedia Commons**

We often take the world for granted, so wrapped up in our own thoughts that we fail to appreciate the complexity of our surroundings, the extreme intricacy of an orchid’s design, the profound depth of a bird’s call. If we look closely enough, it is hard to believe that these marvels are truly real. And if we look even closer, we may question, how did it all come to be?

The answer to this question is hard to believe — it all started with a rock. Asteroids, small airless rocks, are theorized to have contributed the basic building blocks of life to Earth billions of years ago.

In Sept. 2023, NASA’s OSIRIS-REx mission provided support for this theory of the origins of life. The mission returned 121.6 grams of a sample of an asteroid, called Bennu, to Earth. This is the largest asteroid sample ever collected, and research about its nature has led to incredible findings.

An international analysis team led by Dr. Daniel Glavin and Dr. Jason Dworkin at the NASA Goddard Space Flight Center, reported the discovery of ammonia and nitrogen-rich soluble organic matter in the asteroid sample. Additionally, Japanese contributors detected all five nitrogenous bases, molecules required for building DNA and RNA, in the asteroid. By definition, living things are classified as possessing either DNA or RNA. Thus, the detection of the necessary building blocks for these complex molecules is supportive of the theory that life could have originated from asteroids landing on Earth’s surface.

When the Bennu asteroid was compared to previously analyzed asteroids, differences were found in the presence of these molecules, specifically nucleotides, the ratio of purines to pyrimidines, and the density of N-heterocycles, xanthine, hypoxanthine, and nicotinic acid (vitamin B3). The team of analysts explains that these variances could be due to differences in parent bodies, formation pathways, or environments which the asteroids were exposed to in space. For example, it is possible that the Bennu asteroid was exposed to a cold molecular cloud environment, where pyrimidine formation — the biochemical process that creates the essential components of DNA and RNA — is more likely to occur.

The team’s findings present important evidence for the question of the origins of life on Earth. With many different factors affecting the composition of asteroids, it can be hard to believe that these rocks were incidentally formed under optimal conditions to produce our planet’s complex life forms. Further, the observation of nucleotides in asteroids presently raises questions about whether or not Earth is the only planet possessing complex life.

Аs we go about our days, we may try to appreciate our surroundings more deeply, paying attention to life around us and continuing to question, how did it all come to be?