Some NASA engineers believe that the DC-X could provide a solution for a crewed Mars lander. Had a DC-type craft been developed that operated as an SSTO in Earth's gravity well, even if with only a minimum 4–6 crew capacity, variants of it might prove extremely capable for both Mars and Moon missions. Such a variant's basic operation would have to be "reversed"; from taking off and then landing, to landing first then taking off. Yet, if this could be accomplished on Earth, the weaker gravity found at both Mars and the Moon would make for dramatically greater payload capabilities, particularly at the latter destination.