From a TA EC No. 2129 ref: Comet Temple.
Latest update Comet Temple
According to Dr, Mark Kidger, Canary Islands reports:
The last 36 hours have been extremely exciting, but ultimately disappointing with respect to Deep Impact and its consequences. Many people seem to think that in the absence of a major light curve event that there will be none. This may be premature because the third phase of the post-impact light curve has barely started.
Up to now the results have been somewhat unexpected. On impact the reaction from the comet was unexpectedly strong, certainly at the high end of expectations. Observations showed an increase of about 2 magnitudes over 15 minutes after impact, although somewhat surprisingly the amplitude was only slightly larger in 2" aperture than in 5". Coincident with this, there was a brief enhancement of cometary emission lines such as CN. After this the comet has faded again and has stubbornly refused to brighten as the impact debris cloud expanded into the coma. Disappointingly, there is no information about the crater other than it is larger than a house (suggesting that it is well under the 100-m diameter that project experts were predicting as their baseline size for it) and no images of it have been released.
What this suggests is that the dust mantle of the comet was thick and also desiccated. When it expanded into space it carried little or no ice with it (had the dust been rich in ice we would have seen a major brightening from sublimation of ice trapped in the dust) and that only a small amount of ice underneath was volatilised when the crater formed. However, it seems possible that there was significant artesian gas pressure underneath the dust mantle and that when the mantle was breached the release of this pressure contributed to the formation of the plume.
Now, we enter the third stage of the light curve. A significant crater has formed which should have breached the dust mantle exposing fresh ice underneath. This should lead to the formation of a significant new active area on the surface of the nucleus. According to how rapidly heat enters this crater, how efficiently the insulating dust mantle has been cleared, and how much fresh ice has been exposed, the comet should start a slow brightening. If this happens the comet could brighten several magnitudes. A lack of such brightening would suggest that either fresh ice has not been exposed by the impact - either because the crater is too shallow, or because the nucleus's outer layers are poor in ice - or that heat is not reaching the crater floor efficiently, which could happen if the crater is very deep with respect to its diameter.
Observers should thus continue to monitor the comet for activity over at least the next week, although initial indications from post-impact CCD photometry by the "Observadores_cometas" group is that a sustained brightening has not occurred so far.
At present there are no signs that the expected brightening is happening. In fact, results from Swift also show the comet stable at 30% brighter than pre-impact, exactly the same as the amateur CCD results.
Eamonn A
  