Research on Europa's Dust Cloud at The Open University's HVI Laboratory

Abstract

Space in the vicinity of Europa is populated by dust originating from its surface. Fragments of the surface are ejected due to meteoroid hypervelocity impacts (but also they may originate from the sub-surface such as was found on Enceladus). It is assumed that orbit-based detection and analysis of material ejected from the Europan surface may provide an alternative method for sampling Europan material without landing on the surface. Relative impact speeds from these dust sources onto an in-orbit detector would, typically, be about 2 kms -1 . This impact speed is generally too low for complete vapourisation of the impactor/target and the ejecta material could be captured in-situ for further analysis. Our current work is aimed at the development of a new hybrid dust detector for any Europa orbiter as well as an understanding of Europa's dust cloud by mimicing micrometeoroid impact into simulated European regolith/ice. In this paper we present our latest research as well as the facility we have developed as a new laboratory in the field of HVI physics.

Models of dust around Europa and Ganymede

“…Therefore, the cumulative ejecta size distribution is represented in the form N = Ad −B , where N is the number of fragments larger than the fragment size, d. From impact experiments onto Europa surface analogue materials, Miljković et al (2011) suggested that impact ejecta from both pure ice and hydrated minerals fragment in a similar way, and that the fragmentation pattern is independent of impact conditions (such as impact angle). Assuming that these distributions are independent of the impactor size, velocity and incidence angle (Miljković et al, 2009), they can be applied to other impact events, such as dust clouds around Europa and Ganymede. In these previous experiments, the slope of the cumulative ejecta size distribution was B=1.5 (Miljković et al, 2011) for both ice and non-ice materials.…”