  We construct a generalization of Witten's Kaluza-Klein instanton, where a
higher-dimensional sphere (rather than a circle as in Witten's instanton)
collapses to zero size and the geometry terminates at a bubble of nothing, in a
low energy effective theory of M theory. We use the solution to exhibit
instability of non-supersymmetric AdS_5 vacua in M Theory compactified on
positive Kaehler-Einstein spaces, providing a further evidence for the recent
conjecture that any non-supersymmetric anti-de Sitter vacuum supported by
fluxes must be unstable.
