2019/08/20 by Nozair Khawaja, N Khawaja, Frank Postberg +15 · 169 citations
Chemistry · Physics and Astronomy · #Astro and Planetary Science #Astrobiology #Astrochemistry #Astrophysics and Star Formation Studies #Chemistry #Enceladus #Environmental chemistry #Icy moon #Interstellar ice #Interstellar medium #Nitrogen #Organic chemistry #Physics #Planetary Science and Exploration #Saturn
paper · pdf · doi:10.1093/mnras/stz2280
published in Monthly Notices of the Royal Astronomical Society 489(4), 5231-5243 (Oxford University Press)
openalex publication_date 2019/08/20 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/30
ABSTRACT Saturn’s moon Enceladus is erupting a plume of gas and ice grains from its south pole. Linked directly to the moon’s subsurface global ocean, plume material travels through cracks in the icy crust and is ejected into space. The subsurface ocean is believed to be in contact with the rocky core, with ongoing hydrothermal activity present. The Cassini spacecraft’s Ion and Neutral Mass Spectrometer (INMS) detected volatile, gas phase, organic species in the plume and the Cosmic Dust Analyser (CDA) discovered high-mass, complex organic material in a small fraction of ice grains. Here, we present a broader compositional analysis of CDA mass spectra from organic-bearing ice grains. Through analogue experiments, we find spectral characteristics attributable to low-mass organic compounds in the Enceladean ice grains: nitrogen-bearing, oxygen-bearing, and aromatic. By comparison with INMS results, we identify low-mass amines [particularly (di)methylamine and/or ethylamine] and carbonyls (with acetic acid and/or acetaldehyde most suitable) as the best candidates for the N- and O-bearing compounds, respectively. Inferred organic concentrations in individual ice particles vary but may reach tens of mmol levels. The low-mass nitrogen- and oxygen-bearing compounds are dissolved in the ocean, evaporating efficiently at its surface and entering the ice grains via vapour adsorption. The potentially partially water soluble, low-mass aromatic compounds may alternatively enter ice grains via aerosolization. These amines, carbonyls, and aromatic compounds could be ideal precursors for mineral-catalysed Friedel–Crafts hydrothermal synthesis of biologically relevant organic compounds in the warm depths of Enceladus’ ocean.