Observations of Comet 9P/Tempel 1 around the Deep Impact event by the OSIRIS cameras onboard Rosetta

Horst Uwe Keller, Michael Küppers, Sonia Fornasier, Pedro J. Gutiérrez, Stubbe F. Hviid, Laurent Jorda, Jörg Knollenberg, Stephen C. Lowry, Miriam Rengel, Ivano Bertini, Gabriele Cremonese, Wing H. Ip, Detlef Koschny, Rainer Kramm, Ekkehard Kührt, Luisa Maria Lara, Holger Sierks, Nicolas Thomas, Cesare Barbieri, Philippe LamyHans Rickman, Rafael Rodrigo, Michael F. A'Hearn, Francesco Angrilli, Maria Antonella Barucci, Jean Loup Bertaux, Vania da Deppo, Björn J.R. Davidsson, Mariolino de Cecco, Stefano Debei, Marco Fulle, Fritz Gliem, Olivier Groussin, José J. Lopez Moreno, Francesco Marzari, Giampiero Naletto, Lola Sabau, Angel Sanz Andrés, Klaus Peter Wenzel

Research output: Contribution to journalArticlepeer-review

26 Scopus citations


The OSIRIS cameras on the Rosetta spacecraft observed Comet 9P/Tempel 1 from 5 days before to 10 days after it was hit by the Deep Impact projectile. The Narrow Angle Camera (NAC) monitored the cometary dust in 5 different filters. The Wide Angle Camera (WAC) observed through filters sensitive to emissions from OH, CN, Na, and OI together with the associated continuum. Before and after the impact the comet showed regular variations in intensity. The period of the brightness changes is consistent with the rotation period of Tempel 1. The overall brightness of Tempel 1 decreased by about 10% during the OSIRIS observations. The analysis of the impact ejecta shows that no new permanent coma structures were created by the impact. Most of the material moved with ∼ 200 m s-1. Much of it left the comet in the form of icy grains which sublimated and fragmented within the first hour after the impact. The light curve of the comet after the impact and the amount of material leaving the comet (4.5 - 9 × 106 kg of water ice and a presumably larger amount of dust) suggest that the impact ejecta were quickly accelerated by collisions with gas molecules. Therefore, the motion of the bulk of the ejecta cannot be described by ballistic trajectories, and the validity of determinations of the density and tensile strength of the nucleus of Tempel 1 with models using ballistic ejection of particles is uncertain.

Original languageEnglish
Pages (from-to)87-103
Number of pages17
Issue number1
StatePublished - Mar 2007


  • Comet Tempel-1
  • Comets
  • Impact processes
  • coma


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