Diamond phase in space and the possibility of its spectroscopic detection

The eventual presence of the diamond carbon allotrope in space is discussed in numerous theoretical and experimental studies. The review summarizes the principal mechanisms of nanodiamond formation and experimental results of spectroscopic and structural investigations of nano- and microdiamonds from meteorites. The size dependence of diamond spectroscopic properties is discussed. Infrared spectroscopy allows detection of C–H bonds on surfaces of hot nanodiamond grains. Spectroscopic observation of nitrogen-related point defects in nanodiamonds is very challenging; moreover, such defects have never been observed in nanodiamonds from meteorites. At the same time, photoluminescence and, eventually, absorption of some impurity-related defects, in particular, of the silicon–vacancy (SiV) center, observed in real meteoritic nanodiamonds opens the possibility of diamond detection in astronomical observations.