  We study Mott insulators of fermionic alkaline earth atoms, described by
Heisenberg spin models with enhanced SU(N) symmetry. In dramatic contrast to
SU(2) magnetism, more than two spins are required to form a singlet. On the
square lattice, the classical ground state is highly degenerate and magnetic
order is thus unlikely. In a large-N limit, we find a chiral spin liquid ground
state with topological order and Abelian fractional statistics. We discuss its
experimental detection. Chiral spin liquids with non-Abelian anyons may also be
realizable with alkaline earth atoms.
