Life may have originated in asteroids that came crashing down on Earth

Did outer space provide an assist for early life here on Earth?
Chris Young

Could the origins of life have come from small rocks hurtling through space?

Scientists uncovered the last two of the five informational units of DNA and RNA that hadn't yet been discovered in samples from meteorites, a press statement reveals.

The implications are potentially massive, as they show that all of the genetic parts required to form DNA are present in meteorites, meaning they may have reached Earth via space rocks many years ago.

The discovery was made by an international team, including researchers from NASA. Until now, scientists had only found three of the five informational nucleobases required to build DNA and RNA. A recent analysis by a team of scientists led by Associate Professor Yasuhiro Oba of Hokkaido University, Japan, identified the two missing pieces of the puzzle. The researchers published their findings in a paper in Nature Communications.

"We now have evidence that the complete set of nucleobases used in life today could have been available on Earth when life emerged," said Danny Glavin, a co-author of the paper at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

Are the origins of life extraterrestrial?

The newly discovered pair of nucleobases, cytosine and thymine, may have been elusive in previous meteorite sample investigations due to their more delicate structure.

For the latest study, the researchers used cool water to extract the compounds instead of the hot formic acid typically used. This may have helped to prevent the more delicate nucleobases from breaking down during the process. The scientists also used more sensitive analytics, allowing them to pick up smaller traces of the molecules they were seeking.  

The discovery doesn't provide conclusive evidence that the development of life on Earth was assisted by meteorites, but it provides a new avenue of research that could shed new light on the very early development of life on our planet. "This is adding more and more pieces; meteorites have been found to have sugars and bases now," said Jason Dworkin, a co-author of the paper at NASA Goddard. "It's exciting to see progress in the making of the fundamental molecules of biology from space."

This isn't the first time an investigation has shown the building blocks for life can be found on asteroids. Last year, an analysis of JAXA's Hayabusa-1 asteroid sample collected in 2010 showed the presence of water and organic matter. Not only does the new research provide another strong clue, as well as direction for future research, it also provides a new effective method for scientists to extract materials from meteorite samples and analyze them with incredible efficiency.

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