Organic volatiles and water in Oort Cloud comets were investigated at infrared wavelengths. The detected species include H 2 O, CO, CH 3 OH, CH 4 , C 2 H 2 , C 2 H 6 , OCS, HCN, NH 3 , and H 2 CO. Several daughter fragments (CN, OH, NH 2 , etc.) are also measured, and OH prompt emission provides a proxy for water. Long-slit spectra are taken at high spectral dispersion and high spatial resolution, eliminating several sources of systematic error. The resulting parent volatile production rates are highly robust, permitting a sensitive search for compositional diversity among comets. Here, seven OC comets are compared. Six (including Halley) exhibit similar compositions (excepting CO and CH 4 ). Their low formation temperatures (∼30 K) suggest this group probably formed beyond 30 AU from the young sun. However, C/1999 S4 is severely depleted in hypervolatiles and also in methanol, and it likely formed near 5 - 10 AU. C/2001 A2 is discussed briefly to illustrate future prospects.
All Science Journal Classification (ASJC) codes
- Aerospace Engineering
- Astronomy and Astrophysics
- Atmospheric Science
- Space and Planetary Science
- Earth and Planetary Sciences(all)