Tills deposited in arid polar environments retain more attributes of the transportation phase than do tills deposited in the humid polar environment. The difference results from high depositional activity under conditions of abundant meltwater in the humid environment, and only passive deposition during removal of ice by sublimation in the cold arid environment. Structural properties of tills such as fissility and foliation, and clast orientation and dip have a much higher preservation potential in the arid environment than in the humid one. A model of deposition under arid polar conditions is presented. Existing classifications based only on depositional processes do not use the range of information available from tills deposited in arid polar environments. An expanded classification of tills is proposed which utilizes the position of transport, the position of deposition, the process of deposition, and structural properties acquired during transportation.