Primitive meteorites are time capsules, containing dust that may have remained virtually unchanged since the earliest days of the Solar System. The dust is often peppered with tiny diamonds, which probably condensed from a stellar outflow before the birth of the Sun. But uncertainty surrounds the types of star involved.

Anja Andersen and colleagues (Astron. Astrophys. 330, 1080-1090; 1998) have investigated the matter by extracting diamonds from the 1969 Allende meteorite, shown here in greatly magnified clusters. They then analysed the diamonds' spectral and absorption characteristics at various wavelengths, and predict the spectrum of a plausible candidate star (in this case, a type of carbon-rich red giant). With a template against which to compare real stellar spectra, the origin of the diamonds could in principle be revealed.

Things are not so simple, however, for diamonds have a comparatively weak influence on stellar spectra. But other lines of approach may open up because these microscopic gems can act as seeds, and may have become covered with coats of other dust grains. Andersen et al. suggest such coatings might be retained and their composition revealed by sensitive extraction techniques — offering further clues to the diamonds' history.