  We study Josephson junctions made of semiconducting nanowires with Rashba
spin-orbit coupling, where superconducting correlations are induced by the
proximity effect. In the presence of a suitably directed magnetic field, the
system displays the anomalous Josephson effect: a nonzero supercurrent in the
absence of a phase bias between two superconductors. We show that this
anomalous current can be increased significantly by tuning the nanowire into
the helical regime. In particular, in a short junction, a large anomalous
current is a signature for topologically nontrivial superconductivity in the
nanowire.
