Marco Polo was a proposed space mission concept studied between 2005 and 2015 that would return a sample of material to Earth from the surface of a Near Earth asteroid (NEA) for detailed study in laboratories. It was first proposed to the European Space Agency in collaboration with the Japan aerospace exploration agency JAXA. The concept was rejected four times between 2007 and 2015 for the Cosmic Vision programme "M" medium-class missions.

Marco Polo was a mission concept aimed at visiting a small asteroid and returning a sample to Earth for analysis in laboratory. The concept was initially studied by the European Space Agency (ESA) in collaboration with the Japan Aerospace eXploration Agency JAXA, that referred to it as Hayabusa Mk2. Marco Polo was first rejected in June 2007 for the Cosmic Vision program, but was selected for further assessment studies in November 2007.

The in-situ investigation and sample analysis would allow to improve knowledge of the physical and chemical properties of a small Near-Earth object (NEO) which is believed to have kept the original composition of the solar nebula in which planets formed. Thus, it would provide some constraints to the models of planet formation and some information on how life ingredients may have been brought to Earth. Information on the physical structure would help defining efficient mitigation strategies against a potential threatening object.

Small bodies, as primitive leftover building blocks of the Solar System formation process, offer clues to the chemical mixture from which the planets formed some 4.6 billion years ago. Current exobiological scenarios for the origin of life invoke an exogenous delivery of organic compounds to the early Earth. It has been proposed that carbonaceous chondrite matter (in the form of planetesimals or dust) could have brought these complex organic molecules capable of triggering the pre-biotic synthesis of biochemical compounds on the early Earth. Moreover, collisions of NEOs with Earth pose a finite hazard to life. For all these reasons, the exploration of such objects is particularly interesting and urgent.

The Marco Polo proposals were supported by more than 400 scientists worldwide. This concept was in competition for the M1, M2, M3 and M4 missions. It was rejected all four times.

The principal scientific objective of the Marco Polo mission is to return unaltered materials from a Near-Earth object (NEO) for analyses in terrestrial laboratories, and to obtain measurements that cannot yet be performed from a robotic spacecraft:

The mission would allow to:

Marco Polo's first two rejections came in the competitions for the European Space Agency's Cosmic Vision program M1 and M2 missions, which were supposed to be launched in 2018 and 2020, respectively. MarcoPolo-R, as it was then renamed and re-submitted, then lost out in the M3 competition in 2014. The mission was then renamed and re-submitted as MarcoPolo-2D to compete for the M4 opportunity, but it was rejected in March 2015 at the first stage of the competition.