Simulation of ring patterns observed with noctilucent cloud particles

Laboratory simulation of the ring or halo patterns which were found in the electron microscopic examination of noctilucent cloud particles has been attempted. This was done by impacting ice coated nickel particles on collecting surfaces similar to those used in the 1962 rocket sampling of the clouds. Ring patterns similar to those observed on the rocket sampling surfaces have been produced. From the condition necessary to produce these patterns, a formation mechanism is inferred.