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Simulating Hydrogen in the Tiger Stripes of Enceladus

Presentation #313.03 in the session Enceladus (Poster + Lightning Talk)

Published onOct 23, 2023
Simulating Hydrogen in the Tiger Stripes of Enceladus

Molecular hydrogen was detected during Cassini’s final ‘E21’ flyby of Enceladus, providing strong evidence of extraterrestrial chemical disequilibrium and potential habitability at an icy ocean world. The data captured by the spacecraft’s Ion Neutral Mass Spectrometer (INMS) detected variability and ‘pulses’ in the hydrogen density that remain unexplained. In our research utilizing the Direct Simulation Monte Carlo (DSMC) code PLANET we simulate the gas flow of water vapor and molecular hydrogen through the subsurface conduits of Enceladus. We aim to provide an explanation for the source of the unexpected jets of hydrogen emanating from the Tiger Stripes. Our simulations assume the presence of a liquid reservoir or icy cavern underneath the surface of the ice shell that feeds into the conduits below the Tiger Stripes due to a gas pressure build-up at the liquid-gas interface. We use the known surface conditions such as outflow rate, gas mixture proportions, gas speed and temperature to estimate the unknown conditions within the conduit and to observe how the H2 interacts with the water vapor as it condenses and sublimates along the icy wall. Varying the temperature profile of the icy wall and the rates of sublimation and condensation of H2O (initially mixed with H2) can lead to a broad range of unanticipated gas dynamic flows within the conduits. This includes mixed subsonic and supersonic flows, recirculation, and layering of water vapor and hydrogen along the walls. We currently simulate only the flow below the ground. However, as the investigation progresses, we aim to simulate the gas expansion and interaction with the tenuous ‘atmosphere’ of Enceladus in low-gravity conditions.

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