WHAT’S THE STORY?
IT’S the question that has baffled humankind for as long as we have been here – how did life on Earth start? There are still some people who believe it all happened on the third day of the creation narrative in the Book of Genesis, when God commanded the Earth to produce grass and herbs and tree-bearing fruit. The reality is not entirely dissimilar, but for the fact that production of life happened over a vastly longer period of time. Evolution tells us that all life, including ourselves, is descended from micro-organisms produced by this planet around four billion years ago, give or take a few hundred million years.
We know that asteroids and meteorites collided with Planet Earth while it was still in its infancy and they could have brought things such as water and amino acids. These so-called “building blocks of life” have been found in meteorites before. Yet scientists were aware that there was a key piece missing from the meteorite theory – no one had ever found the sugars that were essential for the creation of life actually on a meteorite. But now an international team, mainly from Japan and Nasa, has made exactly that discovery.
SUGAR?
NOT as in Tate and Lyle granulated from your local store, but “ribose and other bio-essential sugars including arabinose and xylose,” as Nasa put it yesterday.
Now that may not sound a big deal to you but sugars such as ribose are crucial for RNA (ribonucleic acid), which copies genetic codes from DNA and delivers them to ribosomes (minute particles consisting of RNA and associated proteins) that are used to build proteins essential for life. In short: no “sugars”, no life. The fact that scientists have now found these sugars on two meteorites suggests that the theory of life “dropping in” from outer space may well be correct.
WHO HAS FOUND THIS OUT?
THE Japanese researchers were from the Department of Earth Science at Tohoku University in Sendai, the Biogeochemistry Program at the Japan Agency for Marine-Earth Science and Technology in Yokosuka and the Institute of Low Temperature Science at Hokkaido University in Sapporo. Researchers in the US worked out of the Solar System Exploration Division at the Nasa Goddard Space Flight Centre in Greenbelt, Maryland.
Since Earth is awash with life, the team had to consider the possibility that the sugars simply came from contamination by terrestrial life, but the presence of a heavier form of carbon proved the sugars could not have come from Earth.
WHAT HAPPENS NEXT?
LEAD research author Yoshihiro Furukawa, of Tohoku University, said: “The research provides the first direct evidence of ribose in space and its delivery 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.”
The discovery is well-timed as Nasa and the Japanese Aerospace Exploration Agency are each going to launch spacecraft soon to visit two asteroids to see if they can extract more “building blocks” such as the aforementioned sugars.
Nasa’s Jason Dworkin, one of the study’s co-authors, explained: “It is remarkable that a molecule as fragile as ribose could be detected in such ancient material.
“These results will help guide our analyses of pristine samples from primitive asteroids Ryugu and Bennu, to be returned by the Japan Aerospace Exploration Agency’s Hayabusa2 and Nasa’s OSIRIS-REx spacecraft.”
Nasa has chosen four potential sites for its OSIRIS-REx spacecraft to fetch a sample of the asteroid Bennu. The goal is to collect a sample of Bennu in mid-2020, and return it to Earth in late 2023.
For many years scientists have been developing the theory of panspermia, the hypothesis that life is distributed throughout the Universe by space dust, meteoroids, asteroids and comets. Today, that theory is beginning to look a lot more plausible.
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