Velocity Dependence of Submicron Ice Grain Rebound, Sticking, Particle Fragmentation, and Impact Ionization up to 2.4 km/s

The impact dynamics of ice grains on surfaces as a function of velocity, including particle breakup and impact ionization, are of intrinsic interest and are critical for the design of future probes to study the ice grain plume around Enceladus. Measurements of the scattering dynamics of ∼700 nm diameter pure water ice grains upon 0.2–2.4 km/s impact with a metal target are reported here. Production of these Enceladus plume grain analogues and their subsequent acceleration to controlled final velocities were performed with an aerosol impact spectrometer. The particle impact and various impact behaviors, including rebound, sticking, particle fragmentation, and impact ionization, were characterized as a function of velocity with an angle-resolved image-charge particle detector. The probability of rebound, sticking, and particle fragmentation was the highest below 400 m/s, between 400 and 800 m/s, and above 800 m/s, respectively. Impact ionization was also observed for impact velocities above 1000 m/s.