While the cake of life was no doubt baked here on Earth, there’s increasing evidence that the batter began mixing in space. The latest ingredients to be discovered off-world are certain sugars that are essential to life, which have now been found in meteorites. This could lend weight to the idea that meteorite impacts are responsible for the origin of life on Earth.
The discovery was made in powdered samples from two meteorites – Northwest Africa 801 (NWA 801), which was found in Morocco in 2001, and Murchison, which was found in Australia in 1969. The researchers analyzed the rocks using gas chromatography mass spectrometry, which helps identify different molecules by their mass and electric charge.
In doing so, the team found sugars like ribose, arabinose and xylose, in concentrations between 2.3 and 11 parts per billion in NWA 801, and between 6.7 and 180 parts per billion in Murchison. These sugars are all important for life, and ribose in particular is a key part of RNA.
“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 Yoshihiro Furukawa, lead author of the study. “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.”
While it might be easy to dismiss the discovery as contamination from Earthly sources, the researchers say that’s unlikely. One reason is that the carbon in the sugar molecules is abundant in a heavier isotope than that usually found on Earth.
If the sugars did come from space, it might help fill in the puzzle of how life got started on Earth. One theory says that the earliest forms of life used RNA instead of DNA, to copy itself and perform other chemical reactions. As things got more complex, the lifeforms could have made the transition to being dominated by DNA.
The fact that the team found abundant RNA sugars in the samples, but no trace of DNA sugars, could support the story. DNA might only have arisen later, here on Earth.
Previous work has detected similar bio-essential sugars floating around in space. Lab-based experiments, set up to mimic interstellar conditions, have managed to create DNA sugars too – but just because it’s possible doesn’t necessarily mean they are created in nature.
The researchers on the new study plan to analyze other meteorites to try to understand how common the extraterrestrial sugars may be. And some of the most promising samples are pristine ones that have never been to Earth yet – Hayabusa2 is now on its way home after collecting samples from asteroid Ryugu, while OSIRIS-REx is due home in 2023 from asteroid Bennu.
The research was published in the journal Proceedings of the National Academy of Sciences.
Source: NASA