Studies of rock and dust from asteroid Bennu delivered to Earth by NASA’s OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification and Security–Regolith Explorer) spacecraft have revealed molecules that, on our planet, are key to life, as well as a history of saltwater that could have served as the “broth” for these compounds to interact and combine.

The findings do not show evidence for life itself, but they do suggest the conditions necessary for the emergence of life were widespread across the early solar system, increasing the odds life could have formed on other planets and moons.

“NASA’s OSIRIS-REx mission already is rewriting the textbook on what we understand about the beginnings of our solar system,” said Nicky Fox, associate administrator, Science Mission Directorate at NASA Headquarters in Washington. “Asteroids provide a time capsule into our home planet’s history, and Bennu’s samples are pivotal in our understanding of what ingredients in our solar system existed before life started on Earth.”

In research papers published Wednesday in the journals Nature and Nature Astronomy, scientists from NASA and other institutions shared results of the first in-depth analyses of the minerals and molecules in the Bennu samples, which OSIRIS-REx delivered to Earth in 2023.

Detailed in the Nature Astronomy paper, among the most compelling detections were amino acids – 14 of the 20 that life on Earth uses to make proteins – and all five nucleobases that life on Earth uses to store and transmit genetic instructions in more complex terrestrial biomolecules, such as DNA and RNA, including how to arrange amino acids into proteins.

Scientists also described exceptionally high abundances of ammonia in the Bennu samples. Ammonia is important to biology because it can react with formaldehyde, which also was detected in the samples, to form complex molecules, such as amino acids – given the right conditions. When amino acids link up into long chains, they make proteins, which go on to power nearly every biological function.

These building blocks for life detected in the Bennu samples have been found before in extraterrestrial rocks. However, identifying them in a pristine sample collected in space supports the idea that objects that formed far from the Sun could have been an important source of the raw precursor ingredients for life throughout the solar system.

“The clues we’re looking for are so minuscule and so easily destroyed or altered from exposure to Earth’s environment,” said Danny Glavin, a senior sample scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and co-lead author of the Nature Astronomy paper. “That’s why some of these new discoveries would not be possible without a sample-return mission, meticulous contamination-control measures, and careful curation and storage of this precious material from Bennu.”

While Glavin’s team analyzed the Bennu samples for hints of life-related compounds, their colleagues, led by Tim McCoy, curator of meteorites at the Smithsonian’s National Museum of Natural History in Washington, and Sara Russell, cosmic mineralogist at the Natural History Museum in London, looked for clues to the environment these molecules would have formed. Reporting in the journal Nature, scientists further describe evidence of an ancient environment well-suited to kickstart the chemistry of life.

Ranging from calcite to halite and sylvite, scientists identified traces of 11 minerals in the Bennu sample that form as water containing dissolved salts evaporates over long periods of time, leaving behind the salts as solid crystals.

Similar brines have been detected or suggested across the solar system, including at the dwarf planet Ceres and Saturn’s moon Enceladus.

Although scientists have previously detected several evaporites in meteorites that fall to Earth’s surface, they have never seen a complete set that preserves an evaporation process that could have lasted thousands of years or more. Some minerals found in Bennu, such as trona, were discovered for the first time in extraterrestrial samples.

“These papers really go hand in hand in trying to explain how life’s ingredients actually came together to make what we see on this aqueously altered asteroid,” said McCoy.

For all the answers the Bennu sample has provided, several questions remain. Many amino acids can be created in two mirror-image versions, like a pair of left and right hands. Life on Earth almost exclusively produces the left-handed variety, but the Bennu samples contain an equal mixture of both. This means that on early Earth, amino acids may have started out in an equal mixture, as well. The reason life “turned left” instead of right remains a mystery.

“OSIRIS-REx has been a highly successful mission,” said Jason Dworkin, OSIRIS-REx project scientist at NASA Goddard and co-lead author on the Nature Astronomy paper. “Data from OSIRIS-REx adds major brushstrokes to a picture of a solar system teeming with the potential for life. Why we, so far, only see life on Earth and not elsewhere, that’s the truly tantalizing question.”

NASA Goddard provided overall mission management, systems engineering, and the safety and mission assurance for OSIRIS-REx. Dante Lauretta of the University of Arizona, Tucson, is the principal investigator. The university leads the science team and the mission’s science observation planning and data processing. Lockheed Martin Space in Littleton, Colorado, built the spacecraft and provided flight operations. NASA Goddard and KinetX Aerospace were responsible for navigating the OSIRIS-REx spacecraft. Curation for OSIRIS-REx takes place at NASA’s Johnson Space Center in Houston. International partnerships on this mission include the OSIRIS-REx Laser Altimeter instrument from CSA (Canadian Space Agency) and asteroid sample science collaboration with JAXA’s (Japan Aerospace Exploration Agency) Hayabusa2 mission. OSIRIS-REx is the third mission in NASA’s New Frontiers Program, managed by the agency’s Marshall Space Flight Center in Huntsville, Alabama, for the agency’s Science Mission Directorate in Washington.

Quelle: NASA

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NASA: 10,000 organic chemicals found on Bennu!

Scientists studying asteroid grains scooped from asteroid Bennu and returned to Earth by NASA’s OSIRIS-REx spacecraft, have found so many precursors to life that they have a new question: why didn’t life form on Bennu billions of years ago, when conditions seemed ripe for it?
“What did Bennu not have that Earth did have?” asked OSIRIS-REx project scientist Jason Dworkin at a NASA press conference elaborating on findings released shortly before in Nature and Nature Astronomy. “This is a future area of study for astrobiologists to ponder, looking at Bennu as a place that had all the ‘stuff’ but didn’t make life,” he says.

Bennu itself isn’t currently hospitable to life. It’s just a rubble pile that coalesced from fragments of an ancient asteroid smashup a billion or two years ago, says Tim McCoy, curator of meteorites at the Smithsonian Institution’s National Museum of Natural History in Washington, D.C.

But the rubble, McCoy says, comes from an asteroid that was once warm enough to have liquid water in its interior. That water, he says, reacted with rock to produce a brine that would have been highly suitable for life as we know it. Evidence of that brine now appears in the samples as salt crystals akin to those found on dry lakebeds on Earth.

Not that Bennu’s parent body was likely to have had lakes. More likely, McCoy says, it had “something like a muddy surface,” with pockets or veins of fluid underneath. “It was within those that the evaporation occurred,” McCoy says. “Water was lost and these minerals were left behind.”
From the diversity of salts in the samples, it was also clear that “the briny fluids underneath the surface of Bennu’s parent body were crammed full of bio-essential elements like phosphorus and sulfur,” added Sara Russell, a cosmic mineralogist at the Natural History Museum, London.
The samples were also rich in ammonia, says Nicky Fox, associate administrator of NASA’s Science Mission Directorate in Washington, D.C. That’s important, she says, because “on Earth ammonia is important to biology because it can react with formaldehyde, which was also found in the sample, to form complex molecules such as amino acids.”

In fact, she noted, the team found 14 of the 20 amino acids used by Earth life to make proteins, as well as all five of the nucleobases life on Earth uses to encode genetic information in DNA and RNA.
All told, says Danny Glavin, a senior scientist for sample return at NASA’s Goddard Space Flight Center, Greenbelt, Maryland, the scientists found more than 10,000 different organic chemicals. “These samples provide a really unique opportunity to explore the prebiotic organic chemistry that occurred in the Solar System prior to the emergence of life,” he says.
This does not mean, however, that the scientists found any evidence that Bennu’s parent body actually hosted life: and before doing other analyses, the scientists indeed looked for it. “We have looked through the Bennu sample at a very fine level—a sort of micron level, which is a millionth of a meter—and we don’t see any cellular structures that you might expect if there were fossils there,” Russell says. Nor, she says, were there any “chemical fossils,”
What the findings do suggest, Fox says, is that conditions necessary for the emergence of life were widespread across the early Solar System. They also support the theory, she and Dworkin says, that asteroids like Bennu were among the sources that delivered water and chemical building blocks for life to the infant Earth—and other worlds like Mars, Europa, Ceres, and Enceladus—early in the history of the Solar System. It is a process, Fox says, that could have “seeded” Earth and other worlds “with all the ingredients they needed to kickstart life.”

Meanwhile, there are mysteries. In addition to the 14 amino acids used by earthly life, Dworkin says, there are many others, probably hundreds, in the sample not used by Earth life. “This tells us a lot about the chemistry that happened to form these different compounds,” he says, “but if I knew why life picked these 20 as opposed to other ones that were available, I’d be booking my flight to Stockholm.”
Meanwhile, the current analyses only looked at about 30 percent of the 120-gram sample returned by OSIRIS-REx. The rest remains in storage, including 7.5 grams that will be archived at -80°C for 50 years, awaiting the development of analytical techniques currently unheard of.

“It’s very early in the process,” Humberto Campins, an asteroid researcher at the University of Central Florida who is part of the OSIRIS-Rex science team but not part of the sample-analysis team told Cosmos. “We’re just scratching the surface.”

Quelle: COSMOS

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Samples from asteroid Bennu show it had minerals crucial to life

The first samples returned from an asteroid to Earth have revealed that one – Bennu – had an ancient brine with minerals crucial to life.

Research published today in Nature shows that water evaporated on Bennu leaving behind a briny broth which would have allowed the ingredients for life to mix and create more complex structures.

Scanning electron microscope images of soda ash found in samples of the asteroid Bennu returned by NASA’s OSIRIS-REx mission. Credit: Rob Wardell, Tim Gooding and Tim McCoy, Smithsonian.

These minerals date to the early formation of the solar system.

“We now know from Bennu that the raw ingredients of life were combining in really interesting and complex ways on Bennu’s parent body,” says co-lead author Tim McCoy, curator of meteorites at the Smithsonian’s National Museum of Natural History in the US. “We have discovered that next step on a pathway to life.”

Bennu’s parent asteroid formed about 4.5 billion years ago at the dawn of the solar system. This body appears to have had pockets of liquid water which evaporated and left behind brines similar to the salty crusts of dry lakebeds on Earth.

NASA launched the OSIRIS-REx mission to asteroid 101955 Bennu in 2016. It reached the asteroid in 2018 with about 120g of material from the surface sent back to Earth, arriving in 2023.

Bennu has sparked interest from astronomers and astrobiologists because of its near-Earth orbit and its carbon-rich composition.

It may help scientists understand how the organic compounds which eventually formed life, reached Earth.

Analyses of the samples from NASA’s OSIRIS-REx mission are being carried out across the world. The Smithsonian’s state-of-the-art scanning electron microscope allowed McCoy’s team to spot microscopic features less than a micrometre across – a hundred times smaller than the width of a human hair.

They found traces of water-bearing sodium carbonate compounds, commonly known as soda ash, in the sample. These compounds have never been directly observed on any other asteroid or meteorite.

Such sodium carbonate compounds occur naturally on Earth in evaporated lakes.

Bennu’s brine is chemically different to those found on Earth. The asteroid’s compounds are rich in phosphorous. It is lacking in boron, which is common in soda lakes on Earth.

Tim McCoy (right), the Smithsonian’s National Museum of Natural History curator of meteorites and the co-lead author on the new paper, with Cari Corrigan (left) examine a scanning electron microscopy. Credit: James Di Loreto, Smithsonian.

“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 says.

A second paper published in Nature Astronomy includes additional findings from the analysis, including the identification of protein-building amino acids in the Bennu samples. There are also 5 nucleobases that make up the molecular composition of RNA and DNA.

Some of these compounds have never been seen in meteorites.

“This is the kind of finding you hope you’re going to make on a mission,” McCoy adds. “We found something we didn’t expect, and that’s the best reward for any kind of exploration.”

Quelle: COSMOS