Mj. Mumma et al., Detection of Co and ethane in comet 21P/Giacobini-Zinner: Evidence for variable chemistry in the outer solar nebula, ASTROPHYS J, 531(2), 2000, pp. L155-L159
Ethane and carbon monoxide were detected in a short-period comet of probabl
e Kuiper Belt origin. Ethane is substantially less abundant compared with H
yakutake and Hale-Bopp, two comets from the giant-planet region of the sola
r nebula, suggesting a heliocentric gradient in ethane in precometary ices.
It is argued that processing by X-rays from the young Sun may be responsib
le.