  A global bifurcation of the blue sky catastrophe type has been found in a
small Prandtl number binary mixture contained in a laterally heated cavity. The
system has been studied numerically applying the tools of bifurcation theory.
The catastrophe corresponds to the destruction of an orbit which, for a large
range of Rayleigh numbers, is the only stable solution. This orbit is born in a
global saddle-loop bifurcation and becomes chaotic in a period doubling cascade
just before its disappearance at the blue sky catastrophe.
