  In order to obtain the substantial information about the surface physics and
thermal property of the target asteroid (162173) 1999 JU3, which will be
visited by Hayabusa 2 in a sample return mission, with the Advanced Thermal
Physical Model (ATPM) we estimate the possible thermal inertia distribution
over its surface, and infer the major material composition of its surface
materials. In addition, the effective diameter and geometric albedo are derived
to be $D_{\rm eff}=1.13\pm0.03\rm~km$, $p_{\rm v}=0.042\pm0.003$, respectively,
and the average thermal inertia is estimated to be about $(300\pm50)\rm~J\cdot
m^{-2}\cdot s^{-0.5}\cdot K^{-1}$. According to the derived thermal inertia
distribution, we infer that the major area on the surface of the target
asteroid may be covered by loose materials, such as rock debris, sands, and so
on, but few bare rocks may exist in a very small region. In this sense, the
sample return mission of Hayabusa 2 is feasible, when it is performed
successfully, it will certainly bring significant scientific information to the
research of asteroids.
