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Carbon and ice make
up a substantial proportion of our Universe. Recent space exploration has shown
that these two chemical species often coexist including on comets, asteroids
and in the interstellar medium. Here we prepare mixtures of C60 fullerene
and H2O by vapor co-deposition at 90 K with molar C60:H2O
ratios ranging from 1:1254 to 1:5. The C60 percolation threshold is
found between the 1:132 and 1:48 samples, corresponding to a transition from
matrix-isolated C60 molecules to percolating C60 domains
that confine the H2O. Below this threshold, the crystallization and
thermal desorption properties of H2O are not significantly affected
by the C60, whereas the crystallization temperature of H2O
is shifted towards higher temperatures for the C60-rich samples.
These C60-rich samples also display exotherms corresponding to the
crystallization of C60 as the two components undergo phase
separation. More than 60 volume percent C60 is required to significantly
affect the desorption properties of H2O. A thick blanket of C60
on top of pure amorphous ice is found to display large cracks due to water
desorption. These findings may help understand the recently observed unusual surface
features and the H2O weather cycle on the 67P/Churyumov–Gerasimenko