A description of the Spanish contribution to the Marco Polo mission and of the mission itself is presented. Marco Polo is a joint European-Japanese mission of sample return from a Near Earth Object (NEO). Submitted to ESA on July 2007 in the framework of the Cosmic Vision 2015-2025, Marco Polo passed the first evaluation process on October 2007. Seventeen Spanish researchers belonging to six Spanish institutes signed the proposal. The mission is planned to visit a primitive NEO, belonging to a class that cannot be related to known meteorite types, to characterize it at multiple scales, and to bring samples back to Earth. Marco Polo will give us the first opportunity for detailed laboratory study of the most primitive materials that formed the planets. This will allow us to improve our knowledge on the processes which governed the origin and early evolution of the Solar System, and possibly of the life on Earth. Three Spanish institutes are involved in the feasibility studies of two instruments: the THERmal MAPper (THERMAP) and the Marco Polo Camera System (MPCS).