| | '''Europa''', the second innermost, is also the smallest of the Galileans. It has very few craters, and thus by [[uniformitarianism|uniformitarian]] criteria it is considered "young." The thick ice sheet that overlays it has fueled speculation, in the scientific community and in [[science fiction]], that it harbors life. The [[Galileo project|Galileo]] spacecraft discovered evidence that Europa has a sub-crust saltwater ocean under a very thin rock-and-ice layer--and in order to prevent the spacecraft from crashing into Europa, rupturing the crust, and contaminating Europa's oceans with earthly [[microbe]]s, Galileo's mission controllers steered Galileo into a crash dive into Jupiter in September of 2003.<ref name=rense>"[http://www.rense.com/general41/galui.htm Galileo Crashes into Jupiter]." ''ABC News Online'', Australian Broadcasting Company, September 21, 2003. Accessed February 20, 2008.</ref><ref name=Macey>Macey, Richard. "[http://www.smh.com.au/articles/2003/09/14/1063478069136.html Galileo's death leap onto Jupiter]." ''Sydney Morning Herald Online'', September 15, 2003. Accessed February 20, 2008.</ref> | | '''Europa''', the second innermost, is also the smallest of the Galileans. It has very few craters, and thus by [[uniformitarianism|uniformitarian]] criteria it is considered "young." The thick ice sheet that overlays it has fueled speculation, in the scientific community and in [[science fiction]], that it harbors life. The [[Galileo project|Galileo]] spacecraft discovered evidence that Europa has a sub-crust saltwater ocean under a very thin rock-and-ice layer--and in order to prevent the spacecraft from crashing into Europa, rupturing the crust, and contaminating Europa's oceans with earthly [[microbe]]s, Galileo's mission controllers steered Galileo into a crash dive into Jupiter in September of 2003.<ref name=rense>"[http://www.rense.com/general41/galui.htm Galileo Crashes into Jupiter]." ''ABC News Online'', Australian Broadcasting Company, September 21, 2003. Accessed February 20, 2008.</ref><ref name=Macey>Macey, Richard. "[http://www.smh.com.au/articles/2003/09/14/1063478069136.html Galileo's death leap onto Jupiter]." ''Sydney Morning Herald Online'', September 15, 2003. Accessed February 20, 2008.</ref> |