QUESTION: By using HST at different wavelenths, would it be possible to make
very crude compositional maps of Pluto?

ANSWER from Marc Buie on May 26,1996:
Absolutely!  In fact, the work we've already done with HST did just this.
We took images in visible light and in ultraviolet light.  Visible light was
chosen to correspond to a color we've studied in detail over the past 40
years.  Ultraviolet light was chosen to be sensitive to the age of the ices
we know exist on the surface.  Weather of the surface on Pluto will tend to
first change the UV brightness so differences between UV and visible light
can be traced back to how fresh the ice is on the surface.  We managed
to collect some tantalizing information on this from the 1994 HST observations.
Unfortunately, we didn't have enough time on the telescope to get good enough
data in the UV to do this job right.  Next time I hope we can do better.