  Polar active particles constitute a wide class of synthetic colloids that are
able to propel along a preferential direction, given by their polar axis. Here,
we demonstrate a generic self-phoretic mechanism that leads to their
spontaneous chiralization through a symmetry breaking instability. We find that
the transition of an active particle from a polar to a chiral symmetry is
characterized by the emergence of active rotation and of circular trajectories.
We show that the instability is driven by the advection of a solute that
interacts differently with the two portions of the particle surface and it
occurs through a supercritical pitchfork bifurcation.
