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S. Miller, B. Barber, T.S. Stallard, J. Tennyson (UCL), L.M. Trafton (U. Texas)
We predict that approximately 10% of the 1.9 \times 1010 J of kinetic energy that will be transferred from the Deep Impact impactor to Comet Tempel-1 will be used up in melting, vaporising and heating water ice. This will be enough to heat approximately 400kg of water to ~1000K. This amount is comparable to the per second water vapour production rate of the comet - but the gas will be much hotter. At 1000K, several hot transitions of H2O will be produced that are not be present in the Earth's atmospheric spectrum.
Weather permitting, these lines will be observed using the United Kingdom InfraRed Telescope (UKIRT). UKIRT is sited on Mauna Kea, Hawaii, and will therefore be able to observe the impact. We will be observing in the K and L windows, using the facility echelle spectrometer, CGS4. Using the relative and absolute strengths of the observed lines, and the extensive UCL water line list, we will derive values for the amount of hot water produced and the temperature it reaches. This will tell us about the partitioning of energy between heating the water ice and other processes.
After impact, it should be possible to follow the temperature / column density evolution of the gas cloud, as it was following the impact of Comet Shoemaker-Levy 9 with Jupiter. It may even be possible to observe Doppler-shifted (w.r.t. Tempel-1) transitions. It should thus be possible to derive the rate at which the water vapour cloud expands, and to what extent Tempel-1's vapours are ejected into space.
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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.