spaceSpace and PhysicsspaceAstronomy

Stardust Older Than The Solar System Found On Asteroid Ryugu

The sample collected by Hayabusa-2 has revealed motes of dust that predate our Sun.


Dr. Alfredo Carpineti

Senior Staff Writer & Space Correspondent

clockAug 16 2022, 13:34 UTC
Color image of Asteroid Ryugu. Image Credit: ISAS/JAXA
Color image of Asteroid Ryugu. Image Credit: ISAS/JAXA

Dust grains older than the solar system have been discovered in samples collected from Asteroid Ryugu. The material was brought back to Earth by the Hayabusa-2 spacecraft from the Japanese Space Agency, and includes one unexpected find.

The team compared the sample from Ryugu with known presolar grains found in carbonaceous chondrite meteorites that have landed on Earth in the past. Only 5 percent of meteorites on Earth contain stardust from before the solar system, and each grain is roughly 1/100th the size of a period on this page. The oldest known is up to 7 billion years old.


As reported in The Astrophysical Journal Letters, Ryugu has all the known types of dust grains that predate the Sun, including a silicate one that is easily destroyed in chemical weathering. This suggested that when Ryugu’s parent body was altered, this grain was somehow shielded.

“The compositions and abundances of the presolar grains we found in the Ryugu samples are similar to what we’ve previously found in carbonaceous chondrites,” co-lead author Larry Nittler, from Arizona State University, said in a statement. “This gives us a more complete picture of our Solar System’s formative processes that can inform models and future experiments on Hayabusa2 samples, as well as other meteorites.”

Ryugu is a small Near-Earth asteroid that orbits the Sun every 16 months. It is a pile of gravel loosely bound by gravity, and came together from a mixture of different asteroids which had within them original stardust present in the presolar nebula.

The Sun is made of interstellar hydrogen polluted by the material spewed out by several supernovae. That “debris” is what ended up making planets and even us. Studying the presolar grains gives insight into the environment from where the Sun was born and they can be tracked using isotopes, slightly different versions of the same element. 


“Different types of presolar grains originated from different types of stars and stellar processes, which we can identify from their isotopic signatures,” co-lead Jens Barosch, from Carnegie's Institution for Science, explained. “The opportunity to identify and study these grains in the lab can help us understand the astrophysical phenomena that shaped our Solar System, as well as other cosmic objects.”

This is just the beginning of the work being done on the samples from Ryugu. More insights are certain to come.

spaceSpace and PhysicsspaceAstronomy
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