QUESTION:
How do you tell the difference between ice formed by methane and ice
formed by water?
 
ANSWER from Jesse Bregman on May 16:
It is fairly easy to tell the difference between water and methane ice
by taking a spectrum.  Each molecule has its own unique "fingerprint"
which shows up as absorption bands in the spectrum (wavelengths or colors
which are dark).  These dark bands are caused when light is absorbed
as it passes through the ices.  Water ice produces a dark band at 6.1
micrometers (in the infrared part of the spectrum), methanol produces
a dark band at 6.8 micrometers, and methane produces a dark band at
7.6 micrometers.  There are other dark bands which these molecules also
produce which helps to identify the composition of the ice.  The
wavelengths for these absorption bands are known from experiments done
in laboratories around the world where spectra are taken of each type
of ice.