We report in situ ion mass spectrometer measurements from the coma of Comet 19P/Borrelly, obtained during the flyby of the Deep Space 1 spacecraft on 22 September 2001. Cometary ions were detected at distances from ∼5.5 × 105 km to 2200 km from the nucleus of the comet. The predominant heavy ions observed during the seven minute interval about closest approach to Borrelly included OH+ (at 57% of the total water-group density), H2O+ (at 29%), O+ (at 13%), CH3+ (at 5%), and CH2+ (at 4%). Of particular note is the small amount of H3O+ (<9%), as this was the most abundant molecular ion observed at closest approach to Comet Halley. This difference is due to the difference in water production rates between the two comets.
All Science Journal Classification (ASJC) codes
- Earth and Planetary Sciences(all)