A situation in which molecules of adsorbate are free to move about the surface. Mobility of the adsorbate will increase with temperature and mobile adsorption may be either localized or non-localized. In localized mobile adsorption the adsorbate spends most of the time on the adsorption sites but can migrate or be desorbed and readsorbed elsewhere. In non-localized adsorption the mobility is so great that a small fraction of the adsorbed species is on the desorption sites and a large fraction at other positions on the surface.