QUESTION:
Why was a tetrahedron shaped craft sent to mars and set down on the
tetrahedron angle of 19.5 degrees north?

ANSWER from Bridget Landry on January 18, 2000:
A tetrahedron was the simplest shape in which to build the
space craft.  It has the fewest sides of any regular solid figure (if
you don't count a sphere), thus minimizing the number of moving parts.

The landing site was chosen as the best source of a wide variety of
rocks, as it was a flood plain.  Billions of years ago, repeated
flooding incidents occurred in that region, dumping soil and rocks
from terrains to the south and southwest on the site where we
eventually landed.  This effectively increased our sampling range by
several orders of magnitude, allowing us to learn a great deal more
than we would have on a relatively unmodified terrain.