7 Minutes
Rare asteroid grains carry ancient chemistry to Earth
Two microscopic fragments returned by JAXA's Hayabusa2 mission are offering scientists an unprecedented look at chemical processes from the earliest days of the Solar System. Collected and delivered to Earth in 2020, these grains originate from different depths of the carbonaceous asteroid Ryugu: one from the exposed surface and one from the interior. Together they function as preserved time capsules, retaining mineralogical and chemical signatures erased long ago on planet Earth by tectonics, weathering and biological recycling.
Only 5.4 grams of Ryugu material were returned in total, and the international research team led by geoscientist Paul Northrup received just 9.3 milligrams for detailed study. Because of that scarcity, non‑destructive, high‑precision imaging and mapping techniques were essential to extract maximum information with minimal sample consumption.
Scientific background and mission context
High-resolution slice of a Ryugu grain showing selenium (red), iron (green), and manganese (blue). (BNL)
Ryugu is a carbonaceous asteroid, a primitive class of bodies rich in organic matter, hydrated minerals and volatile elements. These objects formed in the outer regions of the early Solar System and have experienced comparatively little alteration, so they preserve records of solar nebula chemistry, aqueous reactions, and the inventory of elements that seeded young planets.
Hayabusa2 was designed to return pristine samples to laboratories on Earth. The advantage of sample-return missions is that terrestrial laboratories offer instruments that cannot be flown in space: synchrotron X-ray beamlines, electron microscopes and mass spectrometers that can detect trace elements and map their spatial relationships at submicron scales. Because Earth has recycled most of its earliest crust, asteroidal fragments like Ryugu provide the best remaining archives of primordial Solar System materials.
Mission analysis and imaging methods
Energy map of a Ryugu grain, showing phosphorus, sulfur, and silicon. (Northrup et al., Geosciences, 2025)
Northrup and colleagues applied two complementary X-ray imaging approaches to probe each grain's exterior and interior without destroying the samples. Using advanced, non‑destructive X‑ray mapping and tomographic imaging, the team identified a range of elements and mineral phases including selenium, manganese, iron, sulfur, phosphorus, silicon and calcium. These element maps reveal how elements are spatially associated, a key to reading the history of aqueous alteration and mineral precipitation on the parent body.
Non‑destructive imaging: why it matters
Non‑destructive techniques allow researchers to preserve the limited sample inventory while still resolving chemical heterogeneities at micrometer and submicrometer scales. As Northrup has emphasized, this capability is crucial when hundreds of investigators seek access to minute aliquots of one of the Solar System's most valuable sample sets.
Key discovery: a phosphide plus a novel hydrated phosphate mineral
A notable outcome reported in a 2024 X‑ray study and elaborated in a Brookhaven National Laboratory press release was the identification of phosphorus in two distinct chemical contexts inside Ryugu grains: a phosphate form similar to minerals found in teeth and bones on Earth, and a rarer phosphide form previously not observed in terrestrial geology. Subsequent, more detailed mineralogical analyses later in 2024 uncovered hydrated ammonium magnesium phosphorus (HAMP) in the Ryugu material. HAMP is a crystalline, hydrated ammonium‑magnesium‑phosphate mineral that does not occur naturally on Earth and bears resemblance to struvite, an ammonium phosphate mineral linked to biological processes.
Struvite is commonly associated with biologically mediated precipitation and is a major component of some kidney stones on Earth. The discovery of HAMP in an extraterrestrial sample is striking because it suggests that ammonium, magnesium, and phosphate can assemble into crystalline hydrated phases in space environments under conditions very different from those on our planet.
Implications for phosphorus delivery and prebiotic chemistry
Phosphorus is a key bioessential element involved in energy transfer (ATP), genetic backbone chemistry (DNA and RNA) and cell membranes (phospholipids). Finding phosphate and unusual phosphorus compounds in primitive asteroidal material supports models in which asteroids and meteorites delivered bioavailable phosphorus to the early Earth. The presence of an ammonium‑bearing hydrated phosphate mineral raises new questions about the redox and fluid chemistry on Ryugu's parent body and the ways extraterrestrial minerals could have contributed to prebiotic chemistry on early Earth.
Expert Insight
Dr. Elena Morales, planetary scientist and sample‑analysis specialist (NASA Ames Institute for Astrobiology), adds: 'Discoveries like HAMP show that asteroidal environments can produce mineral assemblages we rarely see on Earth. That expands our view of the chemical pathways available in the young Solar System. Finding ammonium‑bearing hydrated phosphates suggests accessible reservoirs of reduced nitrogen and phosphate existed on small bodies, which could have been delivered to Earth and influenced early organic chemistry.'
This commentary underscores the broader significance of Ryugu samples for questions about chemical evolution and the origin of life. While HAMP itself is not evidence of life, its mineralogy points to aqueous alteration and chemical conditions that can concentrate and transform bioessential elements.
Future prospects and related research
Ongoing analyses of Ryugu grains will combine high‑resolution mineralogy with isotopic studies and organic chemistry surveys. Researchers aim to determine HAMP's precise crystal chemistry, formation temperature and isotopic signatures to constrain the timing and environmental context of its formation. Similar approaches will be used on samples from other returned missions, including NASA's OSIRIS‑REx material from Bennu, enabling comparative planetology across carbonaceous asteroids.
The techniques refined on Ryugu samples — non‑destructive X‑ray mapping, microtomography and targeted microanalysis — will be central to analyzing future precious returns from small bodies and Mars sample caches. As sample collections grow, multidisciplinary teams will be better able to assess how widespread unusual phosphorus minerals are and what they mean for volatile and organic inventories delivered to early planets.
Conclusion
The microscopic grains from asteroid Ryugu preserve mineralogical and chemical evidence of primordial Solar System processes that the Earth no longer retains. Using advanced non‑destructive X‑ray imaging, researchers identified diverse elements and a previously unseen hydrated ammonium magnesium phosphorus mineral (HAMP), alongside other phosphorus species including a rare phosphide. These discoveries sharpen our understanding of how phosphorus — critical for life as we know it — was processed and transported in the early Solar System. Continued study of Ryugu and other returned samples promises to refine models of asteroidal aqueous chemistry, element delivery to Earth and the potential pathways that made our planet chemically habitable.
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