Determine the origin of secondary minerals in cometary materials

Determine whether secondary minerals observed in cometary materials, particularly phyllosilicates and carbonates in UCAMMs, formed through in-situ aqueous alteration on cometary bodies or were inherited from asteroidal parent bodies that underwent hydrothermal alteration.

Background

UCAMMs contain secondary mineral phases, including carbonates reported in earlier work and a phyllosilicate-like phase observed in UCAMM DC16-309. Their compositions and textures are consistent with possible aqueous alteration, but they could also represent material altered on an earlier asteroidal parent body and later transported into the comet-forming region.

The distinction is important because it bears on whether liquid-water alteration can occur within cometary bodies, for example during perihelion passage, or whether the observed hydrated phases record processes that predated comet formation.

References

Whether secondary minerals observed in cometary materials are in-situ alteration products or heritage from asteroidal hydrothermal alteration is questioned here.

— STXM-XANES and TEM analysis of UltraCarbonaceous Antarctic MicroMeteorites (UCAMMs)  (2608.25795 - Guérin et al., 26 Aug 2026) in Section 4.4.1, Aqueous alteration of minerals

Whether this phase formed from aqueous alteration during comet's activity period, or if it was inherited from an already processed parent body is still unclear.

— STXM-XANES and TEM analysis of UltraCarbonaceous Antarctic MicroMeteorites (UCAMMs)  (2608.25795 - Guérin et al., 26 Aug 2026) in Section 5, Summary