High Temperatures in Returning Ejecta from the R Impact of Comet SL9

Sang Joon Kim, M. Ruiz, G. H. Rieke, M. J. Rieke, K. Zahnle

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Observations from ground-based observatories and with the Galileo spacecraft suggest that the flares from the SL9 impacts resulted from ejecta falling back onto Jupiter in ballistic plumes. This explanation is supported by comparing the plume height as a function of time in HST images with the flare light curve. We show that the rotational temperature of CO in the shock from the R impact rose from less than 2000 K near the beginning of the main flare to about 5000 K at its end. This behavior agrees with a simple physical model of ballistic plumes with a mean molecular weight indicating they are 50% or more jovian air. Alternate models involving formation of molecules at the original impact site, or formation of dust grains to initiate the flare, are inconsistent with these measurements. The energy is emitted primarily as a hot continuum, supporting the possibility that finely divided dust grains are heated in the reentry shock and emit to create the flare. Scaling such models to the energy of the K/T event supports proposals that ballistic plumes were responsible for the global disaster associated with it.

Original languageEnglish (US)
Pages (from-to)164-172
Number of pages9
Issue number2
StatePublished - Apr 1 1999


  • Atmosphere
  • Collisional physics
  • Comets: SL9
  • Jupiter

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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