Evidence for water ice and estimate of dust production rate in comet Hale-Bopp at 2.9 AU from the Sun
Altieri, B.; Keller, H. U.; Lellouch, E.; Crovisier, J.; Lim, T.; Bockelee-Morvan, D.; Schmitt, B.; Leech, K.; Hanner, M. S.; Trotta, F.
France, Spain, United Kingdom, United States, Germany
Abstract
We report observational evidence for water ice in comet C/1995 O1 (Hale-Bopp) when it was at 2.9 AU from the Sun, from emission features at 44 and 65 mu m, and possibly an absorption feature at 3.1 mu m, observed with ISO/LWS and PHT. We find that icy grains have mean radii of 15 mu m within a factor of 2, lifetimes of ~ 2 days, a temperature of ~ 153 K, and a total mass of ~ 2x10(9) kg. From investigation of the continuum spectrum at 43-195 mu m, we also infer a production rate of large particles ( ~ 100 mu m) dust of about 4x10(4) kg s(-1) . Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands and the United Kingdom) and with participation of ISAS and NASA.