The thermal and structural evolution of multicomponent ice/mineral sam
ples due to surface radiative heating has been investigated experiment
ally. The components of the samples were water ice, carbon dioxide ice
, and dunite. Starting with originally homogeneous mixtures, we observ
ed the sublimation of different volatiles under low pressure and low t
emperature conditions. This process resulted in the formation of strat
ified samples, containing clearly divided regimes with different chemi
cal composition and cohesivity. A new computer model, developed along
the lines of our previous work, is applied to provide a quantitative d
escription of the observed temperature evolution and stratification wi
thin the samples. These processes may play a key role in the formation
of surface layers of cometary nuclei. Within the ROSETTA mission, sev
eral already accepted experiments aim at a direct (in situ) investigat
ion of just these near-surface layers on the nucleus of Comet P/Wirtan
en. Therefore, both the rather generally applicable thermal model and
the particular results of our laboratory experiments may provide usefu
l support for the design of these experiments. (C) 1997 Academic Press
.