GEMS, hydrated chondritic IDPs, CI‐matrix material: Sources of water in 81P/comet Wild 2

Abstract

So far there is no conclusive evidence for water in the nucleus of 81P/comet Wild 2. Recently magnetite in collected Wild 2 samples was cited as proxy evidence for parent body aqueous alteration in this comet (Hicks et al. ). A potentional source for water of hydration would be layer silicates but unfortunately there is no record, neither texturally nor chemically, for hydrated layer silicates that survived hypervelocity impact in the Wild 2 samples. This paper reports large vesicles in the matrix of allocation C2044,2,41,2,5 from a volatile‐rich type B/C Stardust track. These vesicles were probably caused by boiling water that were generated when hydrated Wild 2 silicates impacted the near‐surface silica aerogel layer. Potential water sources were partially and fully hydrated GEMS (glass with embedded metal and sulfides) and CI carbonaceous chondrite materials among the earliest dusts that experienced hydration and icy‐body formation and long‐range transport and mixing with materials from across the solar system.

The Nature of Low-albedo Small Bodies from 3 μm Spectroscopy: One Group that Formed within the Ammonia Snow Line and One that Formed beyond It

“…Over the same time period, our understanding of comets has deepened immensely thanks to missions like Stardust, Deep Impact, and Rosetta. Analysis of Stardust samples shows intriguing signs that aqueous alteration occurred on comet 81P/ Wild 2, though direct evidence remains elusive (Berger et al 2011;Hicks et al 2017;Rietmeijer 2019). Nuclear spectra of comet 67P/Churyumov-Gerasimenko show absorptions attributed to submicron ice, ammoniated minerals, and organic materials but no evidence of phyllosilicates (Raponi et al 2020), and a qualitative similarity between the spectrum of 67P and some large asteroids has been noted Poch et al 2020).…”