Recent Chemo-morphological Coma Evolution of Comet 67P/Churyumov-Gerasimenko

TL;DR

This study uses VLT/MUSE observations to analyze the evolving dust and gas coma of comet 67P during its 2021 perihelion, revealing distinct structural and compositional trends linked to sublimation and extended sources.

Contribution

It provides detailed spatial and temporal maps of comet 67P's coma, highlighting the role of extended sources and seasonal effects, enriching previous Rosetta mission findings.

Findings

Distinct dust and gas structures linked to coma sources.

Extended NH₂ and CN emissions suggest distributed sources.

Coma dominated by water vapor as indicated by spectral ratios.

Abstract

We present VLT/MUSE observations of comet 67P/Churyumov-Gerasimenko during its 2021 perihelion passage, from which we generated simultaneous maps of dust, [OI], C$_2$, NH$_2$, and CN comae across 12 pre- and post-perihelion epochs. These maps reveal the evolutionary and compositional trends of 67P's coma and further enrich the context and findings of ESA's Rosetta mission. Dust and gas species displayed distinct structures, where NH$_2$ and CN signals were uniquely associated with known dust fans, raising the question of possible correlation to the dust and contributions of extended sources. Localised fitted NH$_2$ scale lengths were 1.5-1.9$\times$ larger than those fitted for the rest of the coma, which is consistent with an extended source component for northern pre-perihelion emissions. In the southern hemisphere, CN was correlated with a prominent and sharp dust structure, potentially revealing an extended source origin via larger dust particles that preserve the CN parent species, as evidenced by higher spectral slopes in the region. Gas maps depicted two distinct evolutionary regimes: (1) evolving H$_2$O ([OI]$^{1}$D) and C$_2$ emissions driven by nucleus sublimation and subsolar insolation, and (2) stable NH$_2$ and CN emissions associated with seasonal dynamics and possible distributed sources. Dust spectral slope maps revealed spectral slope trends consistent with Rosetta findings, while green/red [OI] ratios generally indicate a coma dominated by H$_2$O.