  When deposited on a hot bath, volatile drops are observed to stay in
levitation: the so-called Leidenfrost effect. Here, we discuss drop dynamics in
an inverse Leidenfrost situation where room-temperature drops are deposited on
a liquid nitrogen pool, and levitate on a vapor film generated by evaporation
of the bath. In the seconds following deposition, we observe that the droplets
start to glide on the bath along a straight path, only disrupted by elastic
bouncing close to the edges of the container. Initially at rest, these
self-propelled drops accelerate within a few seconds and reach velocities on
the order of a few cm/s before slowing down on a longer time scale. They remain
self-propelled as long as they are sitting on the bath, even after freezing and
cooling down to liquid nitrogen temperature. We experimentally investigate the
parameters that affect liquid motion, and propose a model, based on the
experimentally and numerically observed (stable) symmetry breaking within the
vapor film that supports the drop. When also the film thickness and the cooling
dynamics of the drops are modeled, the variations of the drop velocities can be
accurately reproduced.
