- NASA’s OSIRIS-REx mission found ingredients for DNA and RNA on the asteroid Bennu.
- The discovery shows asteroids could seed planets with the precursors for life.
- It’s also more evidence that life could arise on the dwarf planet Ceres and Saturn’s moon Enceladus.
NASA probed an asteroid and found an ancient repository of ingredients for life.
The findings, published in two papers in the journals Nature and Nature Astronomy on Wednesday, point to a missing link in the origins of life — on Earth, but also possibly elsewhere.
NASA’s groundbreaking mission to an asteroid
A mission called OSIRIS-REx landed on an asteroid named Bennu in 2020, jammed its arm into the rock’s surface, and scooped up a heaping sample of grit and dust. It was NASA’s first-ever score of fresh, unadulterated asteroid material.
The mission sealed the Bennu sample in a protective capsule in space and shot it back to Earth, where NASA divvied up the stuff to labs all over the world. Now, surprising science results are rolling in.
Not only does Bennu contain evidence of ancient pools of liquid water — it also carries minerals crucial to life, amino acids, and the five nucleobases for DNA and RNA.
As asteroids crash into worlds across the galaxy, “they’re essentially seeding these planets with the necessary ingredients for life,” Tim McCoy, the curator of meteorites at the Smithsonian’s National Museum of Natural History and co-lead of one of the studies, told Business Insider.
That’s promising for the possibility of life on other worlds — including a few within our own solar system.
Clues in tiny grains of asteroid dust
Researchers have spent thousands of hours peering through special electron microscopes, mapping each grain of material from Bennu.
Each millimeter-sized grain takes about a month to map, McCoy said, because it “probably realistically has at least 10,000 mineral grains in it, and you’re just trying to find the one you’re looking for.”
In a sample the size of a bar of soap, “you’re looking for a grain that’s a hundredth the width of a human hair, and there might be one or two of them,” McCoy said.
They found phosphates and clay, which are both essential to the formation of life on Earth. A salty brine also indicated that mineral-rich pools of water had once evaporated from the parent asteroid that Bennu splintered from.
McCoy had expected some water, envisioning Bennu’s parent asteroid spotted with “ancient mud.” Instead, he said, “it was like an ancient mud with pockets of water in it.”
So, not only did the asteroid carry the basic elements for life. It also had the watery environment to help synthesize them into complex ingredients — like the DNA nucleobases that the NASA team discovered.
That synthesis is a key step in the development of life.
After that, nucleobases must interact with phosphates (which were on Bennu) and sugars (which scientists are still looking for in Bennu’s samples) to form the nucleotides that bind to make the double helix of DNA or its single-stranded cousin, RNA. From there, DNA or RNA provides the instructions for cells and, eventually, can evolve self-replicating life.
That doesn’t necessarily mean asteroids are flying around with DNA and small alien bacteria. However, that early pre-life chemistry may have started on an asteroid in space before it crashed into Earth.
Potential for alien life in our solar system
With its water gone, Bennu is probably not conducting life-ingredient chemistry today — but two planetary bodies in our solar system probably are.
The dwarf planet Ceres and the Saturn moon Enceladus both feature salty brines with large bodies of water.
Those water bodies are much bigger and have probably been around much longer than the water on Bennu’s parent asteroid, so the chemical pathway to life “could have gone much further,” McCoy said.
Both are contenders for possible alien life. The Bennu discoveries are another point in their favor.
Asteroid Bennu has more to offer
At the Smithsonian, McCoy said scientists have mapped about 15 millimeter-sized grains of Bennu dust, with hundreds more to go.
“We’re seeing new things in almost every one,” he said, so there are surely more discoveries to come.
While they continue mapping the minerals in each grain, NASA’s Goddard team plans to look for sugars that would be crucial to forming nucleotides McCoy’s team also hopes to find bits of water trapped in the crystalline structure of Bennu’s mineral grains and trace that water’s history, to find clues about how water has moved through the solar system and its planets.
“I mean, that’s one of the great questions: How did we get oceans and life, and why didn’t every other planet get them?” McCoy said. “This may be part of the answer.”
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