Titanium dioxide, TiO2, is on Earth the naturally occurring oxide of titanium, forming minerals such as rutile, anatase, and brookite. TiO2 molecules have recently been identified by radio astronomers in the circumstellar envelope of the evolved star VY Canis Majoris (see Molecules in Space). Rutile traveling-wave masers have been used in very sensitive receivers for radio astronomy (e.g., Yngvesson and Kollberg 1965).
The principal isotope of titanium is 48Ti, but four other stable isotopes are known – 46Ti, 47Ti, 49Ti, and 50Ti. Titanium isotopic anomalies (differences from typical solar system values for the relative abundances of Ti isotopes; see Bernatowicz and Zinner 1997) have been found in meteorites and interpreted as possible evidence for the survival of pre-solar material, possibly interstellar dust grains or material from a nearby supernova explosion. The related molecule, titanium monoxide, TiO, has long been known to...