Deuterium in Comet C/1995 O1 (Hale-Bopp): Detection of DCN

Abstract
Deuterated hydrogen cyanide (DCN) was detected in a comet, C/1995 O1 (Hale-Bopp), with the use of the James Clerk Maxwell Telescope on Mauna Kea, Hawaii. The inferred deuterium/hydrogen (D/H) ratio in hydrogen cyanide (HCN) is (D/H)HCN= (2.3 ± 0.4) × 10−3. This ratio is higher than the D/H ratio found in cometary water and supports the interstellar origin of cometary ices. The observed values of D/H in water and HCN imply a kinetic temperature ≥30 ± 10 K in the fragment of interstellar cloud that formed the solar system.