QUESTION:
How hard is the frozen carbon dioxide surface of the north polar icecap?
What kind of force would be needed to dig into it?  

ANSWER from Bruce Jakosky on January 14, 1999:
This is a question that we really don't know the answer for.  On Earth,
soil that is filled with water which then freezes can be as hard as
concrete.  Or, loose, fluffy snow can be easily dug through with no
effort.
The difference depends on how much water there is and how much soil
there
is, and how well mixed together they are.  In addition, it depends on
whether
the water was put there as a liquid which then froze or as vapor,
travelling
through the pore spaces between soil grains and then freezing out.

The easiest answer to this dilemma may be to use a drill instead of a
digger.
Harder materials still can be drilled into, although it would take
longer.