A simple, novel experiment is suggested to verify the critical ionization hypothesis in space. The experiment involves the isentropic expansion of gas through a carefully chosen nozzle and skimmer so that the formation of dimers and trimers is enhanced. Because of the reduced ionization potentials of these species and because of the increased mass, it is expected that the critical ionization velocity will be lowered considerably even for simple gases such as N2. The release of the gas aboard the space shuttle, whose orbiting velocity is about 7.3 km s-1, will provide the necessary velocity relative to the ambient ions to ionize the dimers and trimers. The advantages of this method over previously tried or proposed methods are briefly discussed.