 Because of the possibility of subsurface liquid oceans on Jupiter 's moons Europa , Ganymede and Callisto , there has been great interest in studying the icy moons in detail . Funding difficulties have delayed progress . The Europa Orbiter was a planned NASA mission to Europa , which was canceled in 2002 . Its main objectives included determining the presence or absence of a subsurface ocean and identifying candidate sites for future lander missions . NASA 's JIMO ( Jupiter Icy Moons Orbiter ) , which was canceled in 2005 , and a European Jovian Europa Orbiter mission were also studied , but were superseded by the Europa Jupiter System Mission . 
 Because of the possibility of subsurface liquid oceans on Jupiter <a href='null_genetive' title='1'><mark>'s</mark></a>moons Europa , Ganymede and Callisto , <a href='dey_it' title='2'><mark>there</mark></a> <a href='uninflect' title='3'><mark>has</mark></a> been great interest in studying the icy moons in detail . Funding difficulties <a href='been_done' title='4'><mark>have</mark></a> delayed progress . The Europa Orbiter was a planned NASA mission to Europa , which was canceled in 2002 . Its main objectives included determining the presence or absence of a subsurface ocean and identifying candidate sites for future lander missions . NASA <a href='null_genetive' title='5'><mark>'s</mark></a>JIMO ( Jupiter Icy Moons Orbiter ) , which was canceled in 2005 , and a European Jovian Europa Orbiter mission <a href='uninflect' title='6'><mark>were</mark></a> also studied , but <a href='uninflect' title='7'><mark>were</mark></a> superseded by the Europa Jupiter System Mission . 
Because of the possibility of subsurface liquid oceans on Jupiter  moons Europa , Ganymede and Callisto , it have been great interest in studying da icy moons in detail . Funding difficulties done delayed progress . TdaEuropa Orbiter was a planned NASA mission to Europa , which was canceled in 2002 . Its main objectives included determining the presence or absence of a subsurface ocean and identifying candidate sites for future lander missions . NASA  JIMO ( Jupiter Icy Moons Orbiter ) , which was canceled in 2005 , and a European Jovian Europa Orbiter mission was also studied , but was superseded by thdauropa Jupiter System Mission .