ISOTOPIC measurements1 in chondritic meteorites have revealed that live 26Al was present in the early solar system. 26Al and other reported isotopic peculiarities2-4 in the meteorite Allende could be attributable to explosive nucleosynthesis, sparking suggestions1-8 that a nearby supernova may have contaminated the early solar nebula. One explanation for isotopic anomalies in early nebular condensates is the injection of supernova grains. An advantage of this mechanism is that it could avoid excessive dilution of the anomalies by the bulk of the nebula. We examine here the early expansion of supernovae to determine the likelihood of grain nucleation and growth. © 1977 Nature Publishing Group.