Microscopic grains of ancient material that predate the birth of our Sun have been found in samples brought back to Earth from the asteroid Ryugu by the Hayabusa2 mission.
It is the conclusion of a new work of an international team led by Jens Barosch and Larry Nittler of Carnegie and published in The Astrophysical Journal Letters.
Named for a Japanese folk tale, Ryugu is a spinning top-shaped near-Earth object that revolves around the sun every 16 months. Hayabusa2 was the first mission to bring material to Earth from a primitive asteroid, offering a single view of chemical composition of the building blocks from which our Solar System was formed.
“Different types of presolar grains originated from different types of stars and stellar processeswhich we can identify from their isotopic signatures,” Barosch explained in a statement. Isotopes are versions of elements with the same number of protons, but different numbers of neutrons.
He added: “The opportunity to identify and study these grains in the laboratory may help us understand the astrophysical phenomena that shaped our Solar System, as well as other cosmic objects”.
Each generation of stars seeds the raw material from which the next generation is born. Like a phoenix rising from the ashes, our Sun originated more than 4.5 billion years ago. of years when a supernova explosion blasted material into a pre-existing cloud of gas and dust, causing it to collapse in on itself. Remnants of this process formed a spinning disk of material around baby sun from which the planets and other objects merged, including the parent bodies that eventually collided with each other and broke apart to become asteroids and meteorites.
The Hayabusa2 samples allow scientists to investigate the composition of Ryugu with sophisticated microanalytical instruments and compare it to material found in primitive meteorites called carbonaceous chondrites that crashed into the Earth.
The team detected all types of previously known presolar grains, including a surprise, a silicate that is easily destroyed by chemical processing which is expected to have occurred in the main body of the asteroid. It was found in a less chemically altered fragment that probably protected it from such activity.
“The compositions and abundances of the presolar grains we found in the Ryugu samples are similar to those we have previously found in carbonaceous chondrites,” explained Nittler, who did this work at Carnegie but recently moved to Arizona State University. . “This we provides a more complete picture of the formative processes of our Solar System that may inform future models and experiments on samples from Hayabusa 2, as well as other meteorites.”
