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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. ==Scientific objectives== 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. The principal scientific objective of the Hayabusa Mk2 mission is to return unaltered materials from a NEO. Hayabusa Mk2 will allow us to analyze the samples in terrestrial laboratory, and to obtain measurements that cannot yet be performed from a robotic spacecraft (e.g. dating the major events in the history of a sample: laboratory techniques can determine the time interval between the end of nucleosynthesis and agglomeration, the duration of agglomeration, time of accumulation, crystallization age, the age of major heating and degassing events, the time of metamorphism, the time of aqueous alteration, and the duration of exposure to cosmic radiation). Moreover, the mission will allow scientists to: *Determine the physical and chemical properties of the target body, which are representative of the building blocks of the terrestrial planets. *Identify the major events (e.g. agglomeration, heating, aqueous alteration, solar wind interactions …) which influenced the history of the target. *Determine the elemental and mineralogical properties of the target body and their variations with geological context on the surface. *Search for pre-solar material yet unknown in meteoritic samples. *Investigate the nature and origin of organic compounds on the target body. *Search for organic compounds which may shed light on the origin of pre-biotic molecules. *Understand the role of minor body impacts in the origin and evolution of life on Earth. NEOs are among the most accessible bodies of the Solar System. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Hayabusa Mk2」の詳細全文を読む スポンサード リンク
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