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<p>Saturn’s moon Enceladus ejects a plume of ice grains and gases originating from a subsurface ocean via fractures near its south pole. The chemical characterization of organic material in such ice grains was previously conducted via the analysis of mass spectra obtained in Saturn’s E ring by Cassini’s Cosmic Dust Analyzer at impact speeds below 12 km s<sup>−1</sup>. Here we present a comprehensive chemical analysis of organic-bearing ice grains sampled directly from the plume during a Cassini fly-by of Enceladus (E5) at an encounter speed of nearly 18 km s<sup>−1</sup>. We again detect aryl and oxygen moieties in these fresh ice grains, as previously identified in older E-ring grains. Furthermore, the unprecedented high encounter speed revealed previously unobserved molecular fragments in Cosmic Dust Analyzer spectra, allowing the identification of aliphatic, (hetero)cyclic ester/alkenes, ethers/ethyl and, tentatively, N- and O-bearing compounds. These freshly ejected species are derived from the Enceladus subsurface, hinting at a hydrothermal origin and involvement in geochemical pathways towards the synthesis and evolution of organics.</p>

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Detection of organic compounds in freshly ejected ice grains from Enceladus’s ocean

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年10月1日

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  • Nozair Khawaja,
  • Frank Postberg,
  • Thomas R. O’Sullivan,
  • Maryse Napoleoni,
  • Sascha Kempf,
  • Fabian Klenner,
  • Yasuhito Sekine,
  • Maxwell Craddock,
  • Jon Hillier,
  • Jonas Simolka,
  • Lucía Hortal Sánchez,
  • Ralf Srama

摘要

Saturn’s moon Enceladus ejects a plume of ice grains and gases originating from a subsurface ocean via fractures near its south pole. The chemical characterization of organic material in such ice grains was previously conducted via the analysis of mass spectra obtained in Saturn’s E ring by Cassini’s Cosmic Dust Analyzer at impact speeds below 12 km s−1. Here we present a comprehensive chemical analysis of organic-bearing ice grains sampled directly from the plume during a Cassini fly-by of Enceladus (E5) at an encounter speed of nearly 18 km s−1. We again detect aryl and oxygen moieties in these fresh ice grains, as previously identified in older E-ring grains. Furthermore, the unprecedented high encounter speed revealed previously unobserved molecular fragments in Cosmic Dust Analyzer spectra, allowing the identification of aliphatic, (hetero)cyclic ester/alkenes, ethers/ethyl and, tentatively, N- and O-bearing compounds. These freshly ejected species are derived from the Enceladus subsurface, hinting at a hydrothermal origin and involvement in geochemical pathways towards the synthesis and evolution of organics.