Get ready for a mind-blowing revelation! NASA's OSIRIS-REx mission has brought us a step closer to understanding the origins of life. The building blocks of RNA, a key molecule for life, have been discovered in asteroid samples, challenging our understanding of life's beginnings.
But here's where it gets controversial... these findings suggest that life's essential ingredients might have originated in space! Imagine that - the very molecules that make up RNA, and possibly even RNA itself, could have been delivered to Earth by asteroids. It's like a cosmic delivery service for the ingredients of life.
Two groundbreaking papers in Nature Geoscience and Nature Astronomy reveal the detection of sugars ribose and glucose, along with a unique carbonaceous "gum," in samples from the near-Earth asteroid 101955 Bennu. This discovery builds upon the earlier identification of amino acids and nucleobases in the Bennu samples, painting a clearer picture of the asteroid's role in life's origins.
And this is the part most people miss... a third paper in Nature Astronomy highlights an abundance of pre-solar grains, dust from before our Solar System's birth, including dust from supernovae. Scientists led by Ann Nguyen found six times more of this supernova dust than typically found in meteorites and other asteroids. Could this suggest variations in the concentration of pre-solar dust grains in the gas and dust disc that formed our Solar System?
The real headline grabber, though, is the discovery of organic materials useful for life, particularly the so-called "space gum." This gum-like substance, a chain of polymers, is unlike anything found in space before. Scott Sandford, co-lead author of the Nature Astronomy paper, describes it as "carbonaceous, but much richer in nitrogen and oxygen than most extraterrestrial materials." It's pliable, bending and dimpling like chewing gum, but its chemical makeup is unique, likely unmatched by anything on Earth.
The extraction process was a delicate affair. Sandford and Zack Gainsforth had to weld a tungsten needle to the sample and reinforce it with micro-scale platinum scaffolding to prevent deformation. Gainsforth explains, "Scott and I made an on-the-fly decision to reinforce the samples based on how they were reacting." This innovative approach allowed them to cut the sample with an ion beam, thinning it to a thousand times thinner than a human hair for further analysis.
The gum's nitrogen is found in nitrogen heterocycles, the building blocks of nucleobases in DNA and RNA. This leads us to another exciting discovery - the sugars ribose and glucose in the Bennu samples. Ribose is a crucial component of the sugar-phosphate backbone in RNA molecules, and its presence, along with glucose, means all the ingredients for RNA assembly are present in the Bennu sample.
But here's a twist - deoxyribose, which is ribose minus one oxygen atom, is notably absent. Deoxyribose in DNA performs a similar role to ribose in RNA, and its absence supports the RNA world hypothesis, suggesting that early life on Earth may have relied on RNA instead of DNA. The presence of all RNA's ingredients on Bennu even raises the possibility that RNA could have formed in space before reaching Earth.
Yoshihiro Furukawa, lead author of the Nature Geoscience paper, explains, "Formation of RNA from its building blocks requires a dehydration reaction, which we can expect to have occurred both in ancient Bennu and on primordial Earth." However, detecting RNA directly is challenging due to its expected low abundance, so for now, the focus is on its ingredients.
These discoveries are monumental in the quest to understand life's origins. Thanks to Bennu and the asteroid 162173 Ryugu, sampled by JAXA's Hayabusa2 mission, scientists are increasingly confident that life's building blocks came from space. But what do you think? Could RNA have formed in space, or is this just a fascinating collection of ingredients? Let's discuss in the comments!
