The asteroid Bennu is puzzling scientists, with samples from the space rock showing weirder properties than they expected. These include extremely high nitrogen levels and improbably magnetic properties.
快猫短视频s have been analysing clumps of rock from Bennu since NASA鈥檚 OSIRIS-REx spacecraft returned samples from the asteroid to Earth in 2023. They quickly found these contained a plethora of the chemical building blocks for life, including particles rich in phosphorus and nitrogen-containing carbon compounds.
When at the University of California, Berkeley, and his colleagues looked at some of these particles more closely, using an electron microscope, they found improbably high amounts of nitrogen, including a compound containing carbon, oxygen and nitrogen with an 鈥渋nsane鈥� amount of almost 20 per cent nitrogen, he says.
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鈥淚f we had found this particle first, we would have chalked it up as contamination, except for the fact that we had seen another [nitrogen-rich] particle already,鈥� says Gainsforth. He presented the findings at the Lunar and Planetary Science Conference (LPSC) in Texas on 10 March.
Researchers were also surprised at the structures that some of these carbon compounds formed. Many asteroids contain nanoglobules, which are tiny, hollow blobs of carbon that can contain important other molecules within them. But in Bennu, these nanoglobules appeared to stick together to form vast structures hundreds of times larger, called macromolecules. 鈥淵ou could see these things with the naked eye in the microscope,鈥� says at NASA鈥檚 Johnson Space Center in Texas. 鈥淭hey were massive, and so we assumed they were something else. We thought it couldn鈥檛 be just massive globules, that would be ridiculous.鈥�
When Clemett and his team analysed these macromolecules, the result of which they also presented at LPSC on 10 March, they found chemical hints that they had formed in extremely cold environments around the time that the sun formed 鈥� four and a half billion years ago 鈥� or even earlier, and they have stayed stuck together ever since.
These macromolecules might have acted as a protective bubble around important elements for life, shielding them from the solar system鈥檚 harsh environments and later delivering them to a forming planet. 鈥淚t鈥檚 a good delivery mechanism,鈥� says Clemett. 鈥淭hese things are relatively robust.鈥� But explaining exactly how so many nanoglobules originally stuck together is still a mystery, he says. 鈥淭he building blocks of these things are all about 300 nanometres, so how you get these things in the first place absolutely baffles me.鈥�
at the Smithsonian Institution in Washington DC was also surprised by the size of them. 鈥淲e鈥檝e never seen these numbers of nanoglobules coming together to make these larger clumps. I think it raises the real question of how big could they get? Could you make metre-sized pieces, basketball-sized pieces?鈥�
Bennu鈥檚 weirdness doesn鈥檛 stop there.聽While at the Carnegie Institution for Science in Washington DC and his colleagues were preparing samples for analysis of their chemical properties, the researchers noticed the samples responded extremely strongly to magnetic fields.
鈥淚 have never seen anything so magnetic in my entire life,鈥� said Cody, who presented their findings at LPSC on 10 March. 鈥淚 had some crushed Murchison [an Australian meteorite] and some crushed Bennu, and I took a big magnet up to the vials and held them there,鈥� he said. 鈥淢urchison just sits there, even though it has a lot of magnetite and [other magnetic compounds], but Bennu would literally race across the vial and climb up the side.鈥�
He says the samples were being prepared for nuclear magnetic resonance, and that it鈥檚 possible that the strong magnet may have magnetised the particles rather than them being intrinsically magnetic to begin with. But he adds that he hasn鈥檛 seen this with effect with 35 other meteorites he has analysed in a similar manner.
Cody and his team are still working to figure out how Bennu came to acquire its magnetic properties, but they don鈥檛 currently have a working theory, he says.
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Mysteries of the universe: Cheshire, England
