The asteroid Ryugu is an echo from the deep, distant past. Two tiny grains of the rock, delivered to Earth in 2020 by the famous Hayabusa2 mission, contain minerals older than any found on our planet.
One grain comes from the asteroid's surface, the other from within. Both are incredible archives of our early Solar System and the chemical reactions that led to its formation.
An X-ray analysis of the two grains was published in 2024 and recently elaborated upon in a press release from Brookhaven National Laboratory at the US Department of Energy.
Related: Asteroid Ryugu Was Once a Planet Forming in The Outer Reaches of Our Solar System
"The beauty of these combined techniques is that we can measure the chemistry of both the exterior and the interior of a sample without damaging it," says project lead and geoscientist Paul Northrup of Stony Brook University in the US.
"This is important to preserve such rare and unique samples, especially when hundreds of researchers are competing for access to so little material."
Here on Earth, geochemical records of the early Solar System have long been wiped from the face of our planet.
Carbonaceous asteroids like Ryugu have escaped the same, harsh planetary conditions, which means they are relatively pristine and uncontaminated.
Each little grain that scientists collected from the asteroid in 2020 is extremely precious. Only 5.4 grams (0.2 ounces) of material exist to analyze, and Northrup and his international team received just 9.3 milligrams in total.
Using two X-ray imaging techniques, the researchers revealed a diversity of minerals and compounds, including selenium, manganese, iron, sulfur, phosphorus, silicon, and calcium.
According to the recent BNL press release, phosphorus was found in Ryugu in two forms: the mineral found in our teeth and bones, and a rare phosphide mineral not present on Earth.
Northrup and team's paper doesn't confirm what this mineral is, but further study of the asteroid material later in 2024 turned up hydrated ammonium magnesium phosphorus (HAMP). This is a crystalline mineral not found on our planet that is most similar to Earthly struvite.
Struvite is closely linked to biological formation, and it is a major part of some kidney stones.
"The finding of HAMP grains in the Ryugu samples continues to highlight the potential role of extraterrestrial matter in originating life on Earth," wrote astrobiologist Matthew Pasek for Nature Astronomy in 2024.
Every grain of data we can mine from Ryugu gets us a step closer to understanding the start of our Solar System.
The study was published in Geosciences.