Scientists have finally had a close look at the rubble collected by a NASA spacecraft from an asteroid. In it, they’ve found new clues about the ingredients for life that were present in the early solar system and how they might have come to Earth.
An international team of scientists has released some of their discoveries about the samples collected by the NASA spacecraft Osiris-REx from the near-Earth carbon-rich asteroid Bennu in 2020 and returned to Earth in 2023.
Bennu, a carbon-rich asteroid that orbits as close as 300,000 kilometres to Earth, was part of an ancestral asteroid that formed in the early solar system about 4.5 billion years ago. Because of that, it can tell scientists what molecules needed for life were present in the early solar system.
“This asteroid is like a frozen time capsule,” said Kim Tait, senior curator of mineralogy at the Royal Ontario Museum in Toronto and co-author of a new study on its mineral composition.
A NASA spacecraft descended to an asteroid and momentarily touched the surface to collect a handful of cosmic dust. Michael Daly, lead scientist for the instrument that mapped the asteroid’s surface, answered some questions from two special guests.
What scientists found on the asteroid
By examining the minerals from the now dry and dusty asteroid, the researchers could tell that it once contained salty water and that there was sodium, chlorides, fluorides, carbonates and phosphates in the salt, they reported Wednesday in Nature. The crystals seemed to form the way they do in salt lakes on Earth.
A separate analysis of molecules important to life found amino acids, including 14 of the 20 used to build proteins in living things. It also found all five nucleobases or building blocks of RNA and DNA, the researchers reported in Nature Astronomy.
“We now know from Bennu that the raw ingredients of life were combining in really interesting and complex ways on Bennu’s parent body,” Tim McCoy, curator of meteorites at the Smithsonian’s Natural Museum of Natural History and lead author of the new mineral study, said in a news release.
Tait said those carbon-based molecules were forming in “very salty, briny water, which we didn’t expect at all.”
The research adds to evidence from meteorites and another asteroid sampling mission, the Japan Space Agency’s Hayabusa2, that space rocks can carry water necessary for life and biological building blocks such as amino acids and nucleobases.
A space capsule that grabbed rare fragments from the asteroid Bennu was successfully dropped back to Earth Sunday. Scientists think the asteroid could contain clues about how life on Earth formed.
What it could mean for the origin of life
The researchers wrote in the Nature study that the conditions that must have existed on the ancient astroid that Bennu came from “pose an intriguing, but untested environment” for forming molecules necessary for life. They suggest conducting experiments to see whether the building blocks of DNA and RNA can form in similar chemical conditions in the lab.
“We now know we have the basic building blocks to move along this pathway towards life, but we don’t know how far along that pathway this environment could allow things to progress,” McCoy said.
Tait added that one of NASA’s priorities is to look for water in space because it’s necessary for life.
“I find that this gets me really excited,” she said, “and I hope it gets other people really excited about the possibilities of other life out there.”
Tait was part of a working group of scientists who met biweekly to discuss and interpret the new results from analyses of different portions of the asteroid sample distributed to labs around the world.
Canada was part of the team for the asteroid return mission because it contributed an instrument used to map the asteroid in order to collect the sample.
While there are signs that places like the planet Mars might once have had water and a warmer climate, Gordon Osinski, a professor at Western University in London, Ont., said the new findings “might mean that … even asteroids may have had the conditions suitable for life.”
A previous chemical sign of water — minerals called hydrated silicates — was found during a scan of Bennu by the OSIRIS-REx spacecraft.
But there’s currently no water on Bennu, and the new study suggests it evaporated sometime in the past.
A NASA spacecraft will attempt to take a sample from the surface of asteroid Bennu, and Canadian technology made it possible to map out the best spot to take the sample.
NASA asteroid landing, asteroid Bennu, Canadian tech NASA, Canada asteroid, NASA asteroid probe, asteroid samples, Canadian space tech, CBC, The National, Aaron Saltzman
One of the other questions related to the origin of life that scientists wanted to explore with this mission was why amino acids, which can come in chemical forms called “left-handed” and “right-handed,” are only found in the left-handed form in living things.
Researchers reported in the new Nature Astronomy study that the amino acids collected from Bennu are in both left-handed and right-handed forms in roughly equal amounts.
Osinski said scientists aren’t entirely sure what that could mean, “but it does kind of partly answer the question” by implying that the left-handedness of amino acids in life on Earth was probably not due to asteroids like Bennu carrying mostly left-handed molecules when they crashed into Earth in the past.
Osinski, who researches how meteorite impacts may have played a role in the origin of life, said scientists have long hypothesized that asteroids may have delivered the building blocks of life to Earth.
And in fact, evidence of water, the building blocks of proteins and the building blocks of DNA and RNA have previously been found on meteorites, including one that landed in Canada.The problem is that meteorites may have been contaminated by water and life on Earth.
The exciting thing about samples from Bennu is that they were collected in space. “And they’re absolutely pristine,” Osinski said. “So we know anything found in these samples came from and was formed either on this asteroid or out there in the solar system.”
