?? ????? ??? ??? ?? ?? ?? ?? ??? ?? ??? ?? ???? ???, ?? ????? ??? ??? ?????.In 2006, a population of comets had been found in the asteroid belt further than the snow line, which can have offered a supply of h2o for Earth's oceans.??, ? ???? ?? ??? ?? ?? ?????, ????? ??? ??? ????? ???? ???, ??? ??? ??? ??? ??? ? ???? ?? ? ?? ??? ?? ??? ???????.?????