Grace Alonewas aplanetoid 53AU fromSol, existing in theKuiper Belt betweenNeptune and theOort Cloud.

A prefabricatedminingcolony existed on the surface, which held a weak but breathableatmosphere due toterraforming. Due to its lower-than-Earthgravity, individuals could bounce about five metres in one step. TheFirst Doctor,Oliver Harper andSteven Taylor encountered theVardans on Grace Alone when they attempted to invade Earth.

Presumably, theTARDIS travellers were meant to die on Grace Alone as they read that theirbodies were found there. Before they could be killed by a Vardan, Oliver absorbed its remaining energy, dispersing himself to save the Doctor and Steven. (AUDIO:The First Wave)