The Market Place

           Becausecometnucleiaresosmall,theyarequitedifficulttostudyfromEarth.Theyalwaysappearatmostasapointoflightineventhelargesttelescope,ifnotlostcompletelyintheglareofthecoma.AgreatdealwaslearnedwhentheEuropeanSpaceAgency,theSovietUnion,andtheJapanesesentspacecrafttoflybyCometHalleyin1986.Forthefirsttime,actualimagesofanactivenucleuswereobtainedandthecompositionofthedustandgasesflowingfromitwasdirectlymeasured.Earlyinthenextcentury,theEuropeansplantosendaspacecraftcalledRosettatorendezvouswithacometandwatchitcloselyforalongperiodoftime.Eventhissophisticatedmissionisnotlikelytotellscientistsagreatdealabouttheinteriorstructureofcomets,however.Therefore,theopportunitytoreconstructtheeventsthatoccurredwhenShoemaker-Levy9splitandtostudywhatoccurredwhenfragmentsweredestroyedinJupiter’satmosphereisuniquelyimportant.