Scientists learning samples from the asteroid Bennu have discovered that it comprises a outstanding mixture of supplies — a few of which shaped lengthy earlier than the solar even existed.
Taken collectively, the findings, described in a trio of lately revealed papers, present how Bennu has preserved clues concerning the earliest days of our photo voltaic system.
“It’s extremely fascinating to see that Bennu is a time capsule of the fabric that was all through the photo voltaic system within the actually, actually early phases of our photo voltaic system,” Pierre Haenecour of the College of Arizona, who analyzed the samples for presolar grains and co-authored the brand new research, advised Area.com in a latest interview.
The samples, which have been scooped up by NASA’s OSIRIS-REx spacecraft throughout a quick but dramatic landing on Bennu in 2020, comprise mud that shaped in our photo voltaic system, natural matter from interstellar area, and stardust older than the solar itself.
Scientists say these tiny grains might have traveled huge distances earlier than turning into a part of Bennu’s mother or father asteroid — a a lot bigger physique that was shattered in a collision tens of millions of years in the past within the asteroid belt between Mars and Jupiter.
“We see that the Bennu pattern is that this leftover of the fabric that was principally throughout the photo voltaic system,” Haenecour advised Area.com. A few of these grains survived excessive warmth and reactions with water, in addition to “a number of generations of influence occasions,” together with the catastrophic collision that broke the mother or father asteroid aside, he mentioned.
One of many research, revealed within the journal Nature Astronomy, reveals that ice contained in the mother or father asteroid melted and reacted with mud, forming the minerals that now make up about 80% of Bennu. Sure grains, similar to silicon carbide, carry distinctive chemical signatures that reveal the kinds of stars they got here from — stars that not exist.
“They’re lengthy gone,” Haenecour advised Area.com. “We would not be capable of observe the celebrities that individual grains got here from.”
These presolar grains are extremely tiny, typically smaller than a micrometer, and are recognized by uncommon chemical fingerprints left by the nuclear reactions of their mother or father stars. Mapping them is like looking for a “needle in a haystack,” however it permits scientists to hint the traditional origins of Bennu’s materials, Haenecour mentioned.
One other research, revealed within the journal Nature Geoscience, highlights how Bennu’s airless floor has been formed by area weathering, together with tiny micrometeorite impacts and the photo voltaic wind. The higher layer of Bennu’s floor has been uncovered to cosmic rays for two million to 7 million years, the research reviews. These processes created microscopic craters and splashes of molten rock on the asteroid’s floor, in accordance with the paper.
Comparability with samples from the asteroid Ryugu, which was sampled by Japan’s Hayabusa2 mission, recommend that impacts might play a bigger function in reshaping asteroid surfaces than beforehand thought, scientists say.
“The floor weathering at Bennu is occurring so much quicker than typical knowledge would have it,” Lindsay Keller, a scientist at NASA’s Johnson Area Middle in Houston who led the paper on area weathering, mentioned in a assertion.
“Area weathering is a vital course of that impacts all asteroids, and with returned samples, we will tease out the properties controlling it and use that knowledge and extrapolate it to elucidate the floor and evolution of asteroid our bodies that we’ve not visited,” Keller added.
As a result of many asteroids expend in Earth’s ambiance, accumulating samples straight from area is crucial to piece their historical past collectively. Meteorites that fall to Earth can present clues about an asteroid’s orbit, however they not often reveal its full historical past, Haenecour mentioned.
OSIRIS-REx studied Bennu up shut for over a yr earlier than accumulating samples, fastidiously mapping its floor and analyzing its minerals, which offered “very worthwhile geological context that we can not get from meteorites,” Haenecour famous.
“We might solely get the solutions we acquired due to the samples,” Jessica Barnes of the College of Arizona, who led one of many new papers, added within the assertion.
“It is tremendous thrilling that we’re lastly in a position to see this stuff about an asteroid that we have been dreaming of going to for therefore lengthy.”
