Europa and Enceladus,
respective moons of Jupiter and
Saturn, are
prime targets in the exploration of potentially habitable extraterrestrial
ocean worlds. Organic material could be incorporated from the ocean
into ice grains ejected from the surface or in potential plumes and
detected via spacecraft flybys with impact ionization mass spectrometers,
such as the SUrface Dust Analyzer (SUDA) onboard Europa Clipper or
the Cosmic Dust Analyzer (CDA) onboard the past Cassini mission. Ice
grains ejected from both Europa and Enceladus are expected to contain
sodium salts, specifically sodium chloride (NaCl), in varying concentrations.
Consequently, it is important to understand its effects on the mass
spectrometric signatures of organic material in salt-rich ice grains.
Previous studies have only focused on the detection of biosignatures,
such as amino acids, in salt-rich ice grains. We here perform analogue
experiments using the Laser Induced Liquid Beam Ion Desorption (LILBID)
technique to study how a wide variety of abiotic and potentially biotic
organic molecules could be identified by SUDA-type instruments. We
investigate their mass spectral characteristics and detectability
at various typical NaCl concentrations expected for salt-rich ice
grains and in both cation and anion modes. Results show that organics
in salt-rich ice grains can still be detected because of the formation
of molecular ions and sodiated and chlorinated species. However, high
salt concentrations induce compound- and concentration-dependent suppression
effects, depending on the chemical properties and functional groups
of the analytes. Our results emphasize the need of both ion modes
to detect a wide range of organics embedded in complex matrices and
to discriminate between abiotic and potentially biotic species. This
work complements a spectral reference library for Europa Clipper and
other ocean world missions.