As a successor of the asteroid explorer “Hayabusa," JAXA is now considering “Hayabusa-2" mission. In addition, a more advanced sample return mission from a minor body is envisaged. This mission is called “Hayabusa Mk2" to distinguish from “Hayabusa-2." Mk2 denotes a model changed one. Researchers in Europe expressed an interest in the Hayabusa Mk2 idea and it was agreed that we would draw up this plan jointly with them. Name of this joint mission is “Marco Polo."
Marco Polo will explore a minor body that is likely to preserve older information than Itokawa and 1999 JU3 of Hayabusa-2 target, and return surface material of such body. This may bring back to us materials present at the birth of the solar system.
<Outline of Mission>
Hayabusa explored the S-type asteroid Itokawa. We plan to explore a C-type asteroid with Hayabusa-2 mission. With the subsequent Marco Pole, we plan to investigate a more primitive D-type asteroid or a comet that no longer releases gases and dust (extinct cometary nucleus ). Since these bodies are located rather far from the earth orbit, we have to power up ion engines. To power up the engines requires more electric power. Accordingly, larger solar array paddles are requested and, naturally, explorer becomes bigger. It is dangerous to make a large explorer close to the surface, so it has to equip with long “legs" to collect surface material. Since velocity of the explorer to return to the earth also becomes fast, a capsule resistant to higher temperature is required. Thus, we need to improve Hayabusa in many aspects.
European team considers that they will deploy a large lander on the minor body's surface to perform more detailed study by directly touching to the surface. A small landing robot like MINERVA for the Hayabusa mission is also under consideration.
By conducting all possible explorations including observations by mother spacecraft, surface investigation by a large lander and/or small landing robot, and sample return from the surface, we intend to investigate in detail a body that is expected to preserve information at the time of the solar system's birth.
<Target to Explore>
Target body to be explored by Marco Polo is now under study, but one of promising candidates is an asteroid named Wilson Harrington that is an extinct cometary nucleus. (In the following figure, blue orbits are of planets from Mercury through Jupiter from inner side and green orbit is of Wilson Harrington.)