We have investigated the likelihood of a high transient mobility for hyperthermal adatoms resulting from dissociative adsorption of a diatomic molecule, in particular O-2 on Al(111), using dynamical simulations on model potentials fitted to available first principle data. We find no evidence for a large transient mobility, compatible with the conclusions by Brune et al. [Phys. Rev. Lett. 68, 624 (1992)], for hyperthermal O atoms moving on the chemisorption potential energy surface for the O/Al(111) system. Our findings are more compatible with the STM results for O-2 on Pt(111). We have also examined the possibility that one of the O atoms moves further away from the surface as a neutral species. That could result in that some O atoms leave the surface as neutral species (abstraction) or extended trajectories along the surface if a weakly bound neutral state for the O atom exists with sufficiently long lifetime.