Organic composition of C/1999 S4 (LINEAR): A comet formed near Jupiter?

In the current paradigm, Oort cloud comets formed in the giant planets' reg ion of the solar nebula, where temperatures and other conditions varied gre atly. The measured compositions of four such comets (Halley, Hyakutake, Hal e-Bopp, and Lee) are consistent with formation from interstellar ices in th e cold nebular region beyond Uranus. The composition of comet C/1999 S4 (LI NEAR) differs greatly, which suggests that its ices condensed from processe d nebular gas, probably in the Jupiter-Saturn region. Its unusual organic c omposition may require reevaluation of the prebiotic organic material deliv ered to the young Earth by comets.