Laboratory experiments for the interpretation of mass spectra from water ice particles measured in-situ onboard Cassini and future space missions

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Most of the dust in the outer solar system is made of water ice with embedded other components. In-situ instruments onboard interplanetary spacecrafts perform TOF mass spectrometry of hypervelocity micro-particle impacts. The interpretation of these spectra strongly relies on laboratory data. In contrast to other compounds, laboratory impact spectra of water ice particles are not yet available although strongly required by ongoing and future space missions. On arrival at Saturn the Cosmic Dust Analyzer (CDA) and the Ion and Neutral Gas Spectrometer (INMS) onboard the Cassini spacecraft for the first time delivered a large amount of in-situ data from water ice. Both experiments showed that the appearance of spectra depends critically on impact velocity and small amounts of varying non-icy material in the grains.We propose an interdisciplinary program, which covers space science and physical chemistry, where mass spectra are simulated by laser pulses onto a water beam with a variety of water solutions and energy densities. First results show that this method is an excellent analogue for impacts of ice particles and molecules with varying speeds onto a detector. The experiments are also suitable to investigate the recently discovered ion formation by charge separation. In parallel there will be a development of a new method, where the shock of the laser is used to actually create high velocity water droplets and ice particles, which then impact onto a twin model of the detectors used onboard space probes. The results are crucial for the Cassini instruments and future space instrumentation, e.g. to comets and the Galilean moons.