A&A 412, 879-891 (2003)
Activity on the surface of the nucleus of comet 46P/WirtanenO. Groussin and P. Lamy
Laboratoire d'Astrophysique de Marseille, BP 8, 13376 Marseille Cedex 12, France
(Received 4 March 2003 / Accepted 6 May 2003)
We present a thermal model of the nucleus of comet 46P/Wirtanen, constrained by the temporal variations of the water production rate, in order to understand the activity on its surface. We consider a spherical nucleus with a macroscopic mosaic of small and numerous active and inactive regions. At heliocentric distances > 1.5 AU, the active regions represent 5-15% of the surface. At ~1.5 AU, a rapid increase takes place and the active fraction reaches 70 to 100% in about 10 days, and then remains approximately constant up to perihelion where molecule s -1. Post-perihelion, this fraction returns to ~10%. The model is consistent with a geometric albedo 0.06. A refractory crust likely forms post-perihelion and can explain the variations of the activity over an orbit. Finally, we derived an erosion of ~0.5 m per revolution and a remaining lifetime for the nucleus of several hundred revolutions.
Key words: comets: individual: 46P/Wirtanen
Offprint request: O. Groussin, firstname.lastname@example.org
© ESO 2003