Rolando Ligustri

The Dust Environment of Comet 67P/Churyumov-Gerasimenko

Comet 67P/Churyumov-Gerasimenko passed its last perihelion on August 2002 and was well observed from fall 2002 to spring 2003. Its most prominent feature was a bright thin dust tail, which is best fitted by the Neck-Line model. Fits of the whole tail provide the dust environment of 67P during a year around perihelion, which is dominated by nucleus seasons. The dust mass loss rate appears constant since 2 AU before perihelion at about 200 kg s−1, a factor 100 higher than 46P/Wirtanen, the previous target of the Rosetta mission. Neck-Line photometry during winter 2002–03 allows us to conclude that such a dust environment remained constant since 3 AU before perihelion, i.e. the distance at which Rosetta science operations will start and the lander will be delivered to the surface.

Dust environment and dynamical history of a sample of short-period comets - II. 81P/Wild 2 and 103P/Hartley 2

Aims. This paper is a continuation of the first paper in this series, where we presented an extended study of the dust environment of a sample of short-period comets and their dynamical history. On this occasion, we focus on comets 81P/Wild 2 and 103P/Hartley 2, which are of special interest as targets of the spacecraft missions Stardust and EPOXI. Methods. As in the previous study, we used two sets of observational data: a set of images, acquired at Sierra Nevada and Lulin observatories, and the A fρ data as a function of the heliocentric distance provided by the amateur astronomical association Cometas-Obs. The dust environment of comets (dust loss rate, ejection velocities, and size distribution of the particles) was derived from our Monte Carlo dust tail code. To determine their dynamical history we used the numerical integrator Mercury 6.2 to ascertain the time spent by these objects in the Jupiter family Comet region. Results. From the dust analysis, we conclude that both 81P/Wild 2 and 103P/Hartley 2 are dusty comets, with an annual dust production rate of 2.8 × 109 kg yr−1 and (0.4−1.5) × 109 kg yr−1, respectively. From the dynamical analysis, we determined their time spent in the Jupiter family Comet region as ∼40 yr in the case of 81P/Wild 2 and ∼1000 yr for comet 103P/Hartley 2. These results imply that 81P/Wild 2 is the youngest and the most active comet of the eleven short-period comets studied so far, which tends to favor the correlation between the time spent in JFCs region and the comet activity previously discussed.