<body bgcolor="#ffffff" text="#000000" link="#0000ff" vlink="#0000ff"> <h2> <center> <font color=green>MOONS OF JUPITER AND SATURN</font> <p> <table border=8 cellpadding=6 bgcolor=lightgreen> <tr> <td> <img src="http://pages.uoregon.edu/~imamura/121/images/jupiter_family.jpeg" width=352></td> <td> <img src="http://pages.uoregon.edu/~imamura/121/images/saturnfamily.jpg" width=600></td> </tr></table> </center> <p><hr><p> <h2> <ul> Both Jupiter and Saturn have extensive satellite systems (for the sake of definition, only large objects are considered moons). There are many interesting aspects of the moon systems, here, I will concentrate on the <font color=magenta>Galilean moons</font> and the moons that are particularly interesting in searches for extraterrestiral life, <font color=magenta>Europa</font>, <font color=magenta>Enceladus</font>, and <font color=magenta>Titan</font>. <p><hr><p> <font color=green> <center> <h2> I. Galilean Moons of Jupiter </center> </font><p> In the early 1600s Galileo Galilei (1564-1642) made extensive observations with one of the first astronomical telescopes. Among his discoveries were <font color=green>the four large moons of Jupiter, the Galilean moons</font>. The smallest moon, <font color=magenta> Europa</font>, is comparable in size to the Moon, the largest, <font color=magenta>Ganymede, </font> is larger than Mercury! The <font color=green>Galilean moons</font> have densities that decrease with increasing distance from Jupiter. <font color=magenta>Io</font> and <font color=magenta>Europa</font> are rock/ice objects and <font color=magenta>Ganymede</font> and <font color=magenta>Callisto</font> are roughly half rock and half ice. The large amount of ice in these moons is understandable (why?) and shows that they contain large amounts of water. <p><font color=magenta> <center>The <font color=green>Galilean moons</font> form a system that mimics the inner Solar System</center></font> <P><center><table><tr> <p><hr><p> <center> <table><tr> <td><img width=370 src="galilean_moons_properties.GIF"></td> <td><img src="galilean_moons_properties_table.jpg"></td> </tr></table></center> <p><hr><p> <font color="magenta"><center> </font></center></td></tr></center> <font color=green><center>II. Io and Active Geology!</font><p> </center> <p> These are all moons (roughly the size of Mercury and smaller). They are thusly expected to have cold interiors and to not have active geologies. Surprisingly, <a href="galilean_moons_io_tidal_heating.mp4"> some of the <font color=green>Galilean moons</font> are among the most geologically active objects in our Solar System.</font></a> Below are pictures of Io showing a plume in eruption and views of the face of Io. Io is the most volcanically active body in our Solar System. <font color=magenta> <center><table><tr> <td width=400><img width=400 src="PIA00583.jpg"></td> <td width=600><img width=400 src="iovolc2.gif"></td> <td width=550><img width=400 src="io4.gif"> </td> </tr></table></center><p><hr><p> <font color=green>Why is Io geologically active?</font><p> <table></table><tr> <td width=500><img width=400 src="galilean_moons_general_tidal-heating.png"> </td> <td width=500><img width=400 src="galilean_moons_io_tidal_heating.gif "></td> <td width=500><img width=400 src="galilean_moons_resonance.gif"> </tr></table></center></a> <p><hr><hr><p> <center><font color=green> III. Water Worlds</font></center> <p> <center><table border=8 cellpadding=8><tr><td> <img width=800 src="hubble_europa.png"> <img width=500 src="enceladus_plumes.jpeg"><p> <h2><center> <a href="http://pages.uoregon.edu/~imamura/121/life/moons.html"> <font color=green>Is there life on the moons of Jupiter and Saturn?</font></a></td></tr></table> </center> <p><hr><p>