The objective of this and a companion ISO proposal (Spectroscopic Studies of Volatile-rich Asteroids) is to investigate the origin of preterrestrial hydrated silicates in a broad cosmochemical context. Here we propose to follow up on the unexpected detection of the 2.7-micron hydrate absorption band in circumstellar dust around SN 1987A (Timmermann & Larson 1992). This observation raised the possibility that oxygen-rich red supergiants might be a primary cosmic source of hydrated silicate dust because SN 1987A's progenitor was an ordinary red supergiant during its evolution before it exploded. This knowledge is important in a general astrophysical context, and it has special relevance to understanding how the composition of the ISM might have influenced thermochemical evolution in our primordial solar nebula. That is, it is not clear whether hydrated silicates that have actually been observed in primitive Solar System objects (e.g., asteroid surface minerals, carbonaceous chondrite meteorites) originated in the ISM or were produced in the solar nebula or the planetesimals themselves. We therefore propose a survey of O-rich red supergiants and other stellar sources where H2O associated with mass loss episodes may have led to the formation of hydrated silicates.