Simulating Europa Clipper Flybys and the Effects on Compositional Mapping by the Surface Dust Analyzer

Abstract:

Given Europa’s lack of atmosphere, its icy surface is continuously bombarded by fast interplanetary micrometeoroids kicking up ejecta material into Keplerian trajectories. This process sustains a steady state “ejecta cloud” near the moon where a dust instrument aboard an orbiting spacecraft can sample grains (~0.2 to 100 micron size range) directly from the surface. In this study, we examine how the Surface Dust Analyzer (SUDA) aboard NASA’s upcoming Europa Clipper mission will make use of this phenomenon to perform compositional mapping of distinct geological features on the surface during several close flybys (~25-50 km at closest approach). SUDA is a dust telescope having two major components: (1) a time-of-flight mass spectrometer revealing the chemical composition of individual ejecta particles and (2) a velocity sensor providing the dynamical properties of the dust or ice grain so that its origin can be determined.

We apply established models that provide the mass and velocity distributions of the ejecta particles. By utilizing Monte Carlo simulations of SUDA detections during a Clipper flyby, we can derive expected results such as the time series of chemical spectra measurements as well as velocity sensor readings. By associating the expected SUDA data to the simulated ejecta sites of origin on the surface, we can inform the flyby requirements (e.g. altitude and proximity of the ground track to a geological feature) that support the science objectives, namely detecting the origin of collected material.

The main purpose of this work is to examine the relationship between the model for ejecta cloud dynamical properties and SUDA’s expected science return from Clipper flybys. The results of the simulations suggest maximum closest approach altitudes and lateral distances of the spacecraft flyby trajectory in relation to the geological feature of interest. We also show how the requirements for the flyby strongly depend on the size of the feature. This will ensure that SUDA will be able to provide unambiguous compositional mapping of geological features such as Thera Macula, a roughly 100 km diameter “chaos region”, which is expected to have a chemical composition distinct from that of its surrounding area.