Nanometer hypervelocity dust impacts in low Earth orbit
journal contributionposted on 13.10.2009, 15:12 by James David Carpenter, T. S. Stevenson, G. W. Fraser, John C. Bridges, A. T. Kearsley, R. J. Chater, Sarah V. Hainsworth
A study has been made of 60 nm thick aluminum films which have been exposed to the space environment outside of International Space Station (ISS) between 2002 and 2004. Field emission scanning electron microscopy has been used to provide high-resolution images of impact features less than 100 nm in diameter and of detailed impact morphologies at different spatial scales. Analysis of images reveals the incident directions and diameters of the impacting particles and allows separation of impacts at hypervelocity from those at lower velocities. This allows the separation of different particle populations. We find that most detected particles have been generated locally as the result of secondaries following larger impacts elsewhere on the ISS or as a result of docking maneuvers by the Progress supply module or by other spacecraft. There is also evidence for a population of dust particles incident at hypervelocity and with minimum diameters smaller than 10 nm. This particle flux of the dust particles is consistent with the expected flux of micrometeoroids with mass >10−18 g at 1 AU and may represent the first measurement of dust particles with such small masses in near-Earth space. Future experiments to measure the flux of nanometer-scale dust particles are proposed, both passive exposure cells for retrieval and also active detectors to provide access to dust/debris populations without the requirement for experiment retrieval.