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Scientists believe they have found a crucial building block of life on an asteroid

Transcript

It's an intriguing finding that suggests life as we know it may have been seeded by asteroids and meteors.

STEVE INSKEEP, HOST:

Scientists think they've found a building block of life, and they found it on an asteroid. A robotic spacecraft returned samples that could provide clues about the beginnings of life on Earth. NPR's Geoff Brumfiel reports.

GEOFF BRUMFIEL, BYLINE: A few years ago, a Japanese spacecraft called Hayabusa2 paid a visit to an asteroid named Ryugu. It's a diamond-shaped chunk of rock about half a mile across. The little Hayabusa spacecraft popped down onto the asteroid surface, snatched a sample and flew back to Earth. Amy Williams is an astrobiologist at the University of Florida. She says that asteroids like this have a lot of organic molecules - not life, but chemical building blocks for life.

AMY WILLIAMS: It's always exciting to have sample return missions because when we can collect samples from where they're made, it actually removes all of the bias of a potential terrestrial contamination.

BRUMFIEL: When she says terrestrial contamination, she's talking about us - life on Earth, smearing our DNA all over the place. One of the big goals is to figure out whether organic molecules from space started life on Earth. Maybe some asteroid impacts brought critical chemicals. Writing in the journal Nature Communications, a team of Japanese scientists now report that the asteroid Ryugu had something on it called uracil. Uracil is a nucleobase like the G's, A's, T's and C's that make up DNA, except uracil is found in RNA. And that's particularly interesting because some scientists suspect life started with RNA.

WILLIAMS: In some models for the evolution of life, there's the idea that RNA was the major genetic information molecule before DNA.

BRUMFIEL: So did uracil arrive on an asteroid? And if it did, did it spark life?

WILLIAMS: If I knew that, then I would be accepting some kind of award.

BRUMFIEL: Researchers are hoping for more answers soon. NASA has its own asteroid sample return mission scheduled to land later this year.

Geoff Brumfiel, NPR News.