Hayabusa Mk2 (Hayabusa Mark2, はやぶさ Mk2, はやぶさ literally meaning "Peregrine Falcon Mark Two") was a proposed Japan Aerospace Exploration Agency (JAXA) space mission aimed at visiting a small primitive asteroid and returning a sample to Earth for laboratory analysis. It was intended to be the follow-on mission to JAXA's Hayabusa mission, as well as the Hayabusa 2 mission. The latest proposal for Hayabusa Mk2 stated its target to be the dormant comet 4015 Wilson–Harrington (1979 VA), with a launch of the probe in 2018. From 2007 to 2010, it was also considered as a joint JAXA-ESA (European Space Agency) mission under the name Marco Polo. The in-situ investigation and sample analysis would allow scientists to improve our 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 planet formed. Thus, it would provide some constraints to the models of planet formation and some information on how life may have been brought to Earth. Information on the physical structure will 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 matter 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.