[Previous] | [Session 44] | [Next]
S.M. Lederer (NASA JSC), H. Campins (Univ. of Arizona), C.M. Lisse (STScI)
We present an analysis of OH, CN, and \rm C2 jets observed in Comet Hale-Bopp during April 22-26, 1997. We conclude that an extended source, which does not peak in productivity at the nucleus, is responsible for the observed morphology in all three species. Sub-micron organic CHON grains are the favored candidate for the extended source. Our model indicates that approximately 40% of the OH, 50% of the \rm C2, and 75% of the CN is produced by the extended source. The balance for each is created by a nuclear gas source. Compared with the nuclear gas source, the composition of the extended source is depleted in OH by a factor of ~4-7, and depleted in \rm C2 by a factor of ~2.
We have constrained the number (5) and the locations of the gas jets necessary to reproduce the observed coma morphology on these dates, for all three species. Four of the five active areas on the comet's surface appear to be emitting the same relative mixture of OH, CN and \rm C2. The fifth area (located at ~12S latitude) is richer in OH than the other active areas. This suggests that the composition of the nucleus is not entirely homogeneous. A high thermal inertia, which would allow production of the radicals throughout the cometary night, is not necessary to explain the existence of the anti-sunward gas jets. Instead, active areas that exist in near-twilight conditions throughout the comet's rotation period produce the bulk of the anti-sunward morphology.
This work was supported by NASA.