1) what is responsible for the fact that the terrestrial planets have similar internal structure? a) gravity b) pressure c) temperature d) friction 2) unlike the terrestrial planets, the jovian planets are characterized by a made up of small solid rock particles a) gaseous atmosphere b) planetary ring system c) network of moons d) large revolving weather mass 3) star formation is triggered when a molecular cloud of is squeezed by an external event a) gas b) dust c) cloud cover d) heat 4) orbit stars other than the sun a) extrasolar planets b) dwarf planets c) jovian planets d) nebular planets 5) whereas asteroids are comprised primarily of comets are comprised primarily of a) rocky material; icy material b) permafrost; molten rock c) icy material; rocky material d) dark cloud; planetary fragments