  We study the singular homology (with field coefficients) of the moduli stack
of stable n-pointed complex curves of genus g (the Deligne-Mumford
compactification). Each of its irreducible boundary components determines via
the Pontrjagin-Thom construction a map to a certain infinite loop space whose
homology is well understood. We show that these maps are surjective on homology
in a range of degrees proportional to the genus. This implies the existence of
many new torsion classes in the homology of the moduli stack.
