A thermal model is introduced that describes the temperature and activ
ity behavior of an insolated porous ice-dust mixture. The results are
compared with measurements during the comet simulation experiments KOS
I 9 and KOSI 10. From the comparison of theoretical with experimental
results thermal properties of the KOSI samples and the nature of the d
ust mantle formation are derived. The differences and similarities bet
ween KOSI results and cometary physics are discussed.