Department of Earth Sciences

Analogue mass spectra collected at Freie Universität crucial for the Interpretation of SUDA data

To ensure the best possible performance of the SUDA instrument at Europa and a smooth interpretation of its data, calibration of the instrument is required. To this end, laboratory experiments have been performed in the laboratory facility of the Planetary sciences group at Freie Universität Berlin using laser desorption experiments. These experiments simulate the impact ionization taking place in the hypervelocity impacts (velocities > 1km/s) of μm-sized dust particles onto space detectors such as SUDA. This laboratory technique is also heavily used for the analysis of the data of the Cosmic Dust Analyzer from the Cassini mission (the predecessor instrument of SUDA), as it allows the simulation of icy impact ionization spectra with varying impact energy and composition. The analogue mass spectra recorded so far allowed to better understand the salt and organic composition of the ocean of Enceladus. A range of different material relevant for icy ocean moons is currently being investigated, including both inorganic and organic compounds but also more complex samples relevant for astrobiology investigations.

• microbial material, such as bacteria cells, spores and extracted cell compounds
  → Recent publications by Klenner et al. (2024) have shown that spectral signals from bacteria cells are clearly identifiable by SUDA, even if an ice grain contains much less than one cell. Dannenmann et al. (2023) demonstrated that bacterial biosignatures such as DNA nucleobases are detectable down to ppm concentrations, and also investigated salty matrices with different NaCl concentrations.

• natural samples for terrestrial analogue environments such as Antarctica

• the products of hydrothermal reactions performed to simulate hydrothermal conditions in Europa or Enceladus interiors
  → A newly developed setup for hydrothermal simulations has been established and recently had successful first results with peptides.

• the products of irradiation experiments simulating the surface conditions on Europa or Enceladus.

The analogue mass spectra recorded in these laboratory experiments are stored in a database for impact ionization mass spectrometers, that will be crucial for the interpretation of SUDA data but also future instruments. More recently, we also investigate the processes of ionization and fragmentation with quantum chemical computations using density functional theory to add theoretical context to impact ionization mass spectrometry.