More evidence that asteroids may have delivered ingredients for life to Earth

The team, led by Associate Professor Yasuhiro Oba of Hokkaido University, Hokkaido, Japan, have now identified the final two nucleobases that have eluded scientists. This newly discovered pair of nucleobases - cytosine and thymine - has been elusive in previous analyses likely because of their more delicate structure, which may have degraded when scientists previously extracted samples.

A new discovery has provided more evidence that chemical reactions in asteroids can make some of life's ingredients, which could have been delivered to ancient Earth by meteorite impacts or perhaps the infall of dust, NASA said in a press release on Tuesday.

Until now, scientists scouring extraterrestrial samples had only found three of the five informational units of DNA and RNA, called nucleobases, that make up life today. Nucleobases belong to classes of organic molecules called purines and pyrimidines, which have a wide variety.

The team, led by Associate Professor Yasuhiro Oba of Hokkaido University, Hokkaido, Japan, have now identified the final two nucleobases that have eluded scientists. This newly discovered pair of nucleobases - cytosine and thymine - has been elusive in previous analyses likely because of their more delicate structure, which may have degraded when scientists previously extracted samples.

Given their delicate structure, researchers used cool water to extract the compounds instead of hot formic acid - which could have destroyed these fragile molecules in previous samples - and more sensitive analytics were employed that could pick up on smaller amounts of these molecules.

"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.

The new discovery provides a proof of concept for a more effective technique to extract information from asteroids in the future, especially from the samples of asteroid Bennu which will be delivered to Earth via NASA's OSIRIS-REx mission next year.

Where does life come from? A new discovery gives more evidence that asteroids & meteorites may have delivered ingredients for life to Earth. Scientists have found the last 2 of 5 informational units of DNA & RNA that had yet to be discovered in meteorites! https://t.co/LINQqNZPzp pic.twitter.com/49rhnqFlpc

— NASA Solar System (@NASASolarSystem) April 26, 2022