37th DPS Meeting, 4-9 September 2005
Session 44 Deep Impact B
Poster, Wednesday, September 7, 2005, 6:00-7:15pm, Music Recital Room

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[44.07] Deep Impact experiment and modelling of cometary nuclei

J-M. Petit (CNRS), U. Marboeuf, O. Mousis (Obs. de Besancon)

Using the 1D cometary nucleus model developed by Espinasse et al. (1991), we calculate the thermodynamical evolution of Comet 9P/Tempel 1 over a period of 360 years corresponding to the time when the orbit is rather well known. Starting from an initially amorphous cometary nucleus which incorporates an icy mixture of H2O and CO, we estimate that, at the time of the Deep Impact collision, the ice would have crystallized to a depth largely exceeding the expected depth of the resulting crater. Hence, the subsurface exposed to space should not be primordial. We also attempt an order-of-magnitude estimate of the heating and material ablation effects on the crater activity caused by the 370 Kg projectile released by the DI spacecraft. We show that the deposited energy is too low to produce any noticeable heating of the nucleus, and hence plays no role in the evolution of crater activity. Using our best estimates, before impact, of the physical and chemical properties of the nucleus and of the expected crater, we calculate that the CO production rate from the impacted region should increase by up to several hundreds times compared the the unperturbed case. In the same time, the H2O production rate decreases by several orders of magnitude at the crater base, making CO the dominant element produced just after impact in the crater.

The author(s) of this abstract have provided an email address for comments about the abstract: petit@obs-besancon.fr

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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.