Editing Comet Shoemaker–Levy 9 (section)

== Post-impact analysis ==
[[File:Impact site of fragment G.png|thumb|225px|A reddish, asymmetric ejecta pattern]]

{{Anchor|calculation2016-01-26}}Several models were devised to compute the density and size of Shoemaker–Levy 9. Its average density was calculated to be about {{convert|0.5|g/cm3|abbr=on}}; the breakup of a much less dense comet would not have resembled the observed string of objects. The size of the parent comet was calculated to be about {{convert|1.8|km|abbr=on}} in diameter.<ref name=Solem1995>{{cite journal|last=Solem|first=J. C.|year=1995|title=Cometary breakup calculations based on a gravitationally-bound agglomeration model: The density and size of Comet Shoemaker-Levy 9 |journal=Astronomy and Astrophysics|volume=302|issue=2|pages=596–608 |bibcode = 1995A&A...302..596S }}</ref><ref name=Solem1994>{{cite journal|last=Solem|first=J. C.|year=1994|title=Density and size of Comet Shoemaker–Levy 9 deduced from a tidal breakup model|journal=Nature|volume=370|issue=6488|pages=349–351 |bibcode = 1994Natur.370..349S |doi = 10.1038/370349a0|s2cid=4313295|url=https://zenodo.org/record/1233164}}</ref> These predictions were among the few that were actually confirmed by subsequent observation.<ref>
{{cite book
 |last1        = Noll
 |first1       = Keith S.
 |last2       = Weaver
 |first2      = Harold A.
 |last3       = Feldman
 |first3      = Paul D .
 |year        = 2006
 |title       = Proceedings of Space Telescope Science Institute Workshop, Baltimore, MD, May 9–12, 1995, IAU Colloquium 156: The Collision of Comet Shoemaker-Levy 9 and Jupiter
 |publisher   = [[Cambridge University Press]]
 |url         = http://www.cambridge.org/us/academic/subjects/astronomy/planetary-science/collision-comet-shoemaker-levy-9-and-jupiter-iau-colloquium-156
 |url-status     = dead
 |archive-url  = https://web.archive.org/web/20151124095115/http://www.cambridge.org/us/academic/subjects/astronomy/planetary-science/collision-comet-shoemaker-levy-9-and-jupiter-iau-colloquium-156
 |archive-date = November 24, 2015
 |df          = mdy-all
}}</ref>

One of the surprises of the impacts was the small amount of water revealed compared to predictions.<ref>{{cite book |title=The Planetary Scientist's Companion |last=Loders |first=Katharina |author2=Fegley, Bruce |year=1998 |publisher=[[Oxford University Press]] |isbn=978-0-19-511694-6 |page=200 |chapter-url=https://books.google.com/books?id=qTZAyOF8J4wC&q=Comet+Shoemaker-Levy+9,+water,+impact,+small+amount |chapter=Jupiter, Rings and Satellites}}</ref> Before the impact, models of Jupiter's atmosphere had indicated that the break-up of the largest fragments would occur at atmospheric pressures of anywhere from 30 [[Pascal (unit)|kilopascals]] to a few tens of [[Pascal (unit)|megapascals]] (from 0.3 to a few hundred [[bar (unit)|bar]]),<ref name="Hu">{{cite journal |last1=Hu |first1=Zhong-Wei |date=May 1996 |title=On Penetration Depth of the Shoemaker–Levy 9 Fragments into the Jovian Atmosphere |journal=Earth, Moon, and Planets |volume=73 |issue=2 |pages=147–155 |bibcode=1996EM&P...73..147H |doi=10.1007/BF00114146 |last2=Chu |first2=Yi |last3=Zhang |first3=Kai-Jun|s2cid=122382596 }}</ref> with some predictions that the comet would penetrate a layer of water and create a bluish shroud over that region of Jupiter.<ref name="Bruton1.5" />

Astronomers did not observe large amounts of water following the collisions, and later impact studies found that fragmentation and destruction of the cometary fragments in a [[meteor air burst]] probably occurred at much higher altitudes than previously expected, with even the largest fragments being destroyed when the pressure reached {{convert|250|kPa|0|abbr=on}}, well above the expected depth of the water layer. The smaller fragments were probably destroyed before they even reached the cloud layer.<ref name="Hu" />