  Given a complex curve C of genus 2, there is a well-known relationship
between the moduli space of rank 3 semistable bundles on C and a cubic
hypersurface known as the Coble cubic. Some of the aspects of this is known to
be related to the geometric invariant theory of the third exterior power of a
9-dimensional complex vector space. We extend this relationship to arbitrary
fields and study some of the connections to invariant theory, which will be
studied more in-depth in a followup paper.
