Much of Earth's space dust may originate from unidentified near-Earth asteroids, study finds

A recent study published on July 7, 2026, reveals that much of Earth's 'space dust' may originate from unidentified near-Earth asteroids. Researchers have identified a new subset of cosmic spherules, termed SCumPo, which may provide clues to their mysterious origins.

Understanding Space Dust and Its Origins

Space dust, primarily composed of micrometeorites, serves as a valuable source for researchers studying cosmic materials. However, pinpointing the origins of these samples can be challenging, especially when their parent bodies are not cataloged. The study, published in Science Advances, highlights a new category of space dust with unknown origins.

Cosmic spherules, which melt during atmospheric entry, lose their original mineral structure, complicating their identification. Approximately 10% of these spherules, referred to as 'Group 4,' exhibit unique oxygen-16 isotope signatures that do not correlate with existing meteorite groups. The study's authors suggest that orbital parameters may assist in determining their sources.

New Findings on SCumPo Cosmic Spherules

The research team analyzed ten SCumPo cosmic spherules from Antarctica and urban rooftops, employing electron microscopy and microprobe chemistry to assess their textures and mineral compositions. The findings revealed similarities between both collections, leading to the definition of SCumPo as a sulfur-rich cumulate olivine cosmic spherule subset.

This subset is closely associated with the oxygen-16-poor Group 4 signature, indicating extremely reducing conditions during atmospheric entry. Key features include:

• Near-absence of magnetite
• Presence of iron-nickel-sulfur droplets
• Low nickel content in olivine crystals
• Unusually sulfur-rich glass

Some spherules displayed both oxygen-16-poor and oxygen-16-rich signatures, suggesting a composite origin.

Potential Parent Bodies and Future Research

To further investigate the origins of SCumPo, the researchers conducted numerical simulations to estimate entry speeds and orbital eccentricities. Results indicated that olivine settling likely occurs at high encounter speeds of approximately 14–17 km/s, suggesting an eccentric orbit typical of near-Earth objects.

The study theorizes that the parent body of SCumPo may be a previously unsampled, primitive, sulfide-rich carbonaceous asteroid related to the CM–CO–CY chondrite clan. The authors note, "Given that we have linked their composition to the CM-CO-CY clan of carbonaceous chondrites, it is plausible that their parent body was a primitive carbonaceous asteroid that migrated onto an Earth-crossing orbit." This discovery highlights a potential missing meteorite type, indicating that while micrometeorite samples exist, no corresponding meteorite has been recorded.