Far‐UV emissions from the SL9 impacts with Jupiter

Observations with the International Ultraviolet Explorer (IUE) during the impacts of the fragments of comet D/Shoemaker‐Levy 9 with Jupiter show far‐UV emissions from the impact sites within a ∼10 min time scale. Positive detections of H 2 Lyman and Werner band (1230–1620 Å) and H‐Lyα emissions are made for impacts K and S, and marginally for P2. No thermal continuum is observed. The radiated far‐UV output was >10 21 ergs. The H 2 spectrum is consistent with electron collisional excitation if significant CH 4 absorption is included. Such emissions could result from plasma processes generated by the impacts. Non‐thermal excitation by the high altitude entry and explosion shocks may also be relevant. Emissions by Al + (1671 Å) and C (1657 Å) of cometary origin are tentatively identified.