The Galilean Satellites

1. The Galilean Satellites • Jupiter has four planetary-sized moons first seen by Galileo and easily visible in binoculars.

2. The Galilean Satellites • Jupiter has four planetary-sized moons first seen by Galileo and easily visible in binoculars.

3. The Galilean Satellites • Jupiter has four planetary-sized moons first seen by Galileo and easily visible in binoculars.

4. Origin of the Galilean Satellites • These large “regular” satellites of Jupiter probably formed in a miniature version of the Solar Nebula around Jupiter as Jupiter itself was forming. • Like the Solar System the inner Jovian moons are rocky and the outer ones are icy.

5. Origin of the Galilean Satellites • These large “regular” satellites of Jupiter probably formed in a miniature version of the Solar Nebula around Jupiter as Jupiter itself was forming. • Like the Solar System the inner Jovian moons are rocky and the outer ones are icy.

7. Ganymede • Ganymede is the Solar System's largest moon and is a bit larger than the planet Mercury.

8. Ganymede • It has a density of 1.9 g/cm3, suggesting a rocky core and icy mantle and exterior

9. Ganymede • It has a density of 1.9 g/cm3, suggesting a rocky core and icy mantle and exterior.

10. Ganymede • Fresh craters expose bright ice. • Darker = older !

11. Ganymede • Ganymede exhibits two terrains • one is dark and heavily cratered • the other is young and marked by parallel ridges/grooves.

12. Ganymede • Ganymede exhibits two terrains • one is dark and heavily cratered • the other is young and marked by parallel ridges/grooves.

13. Ganymede • Ganymede exhibits two terrains • one is dark and heavily cratered • the other is young and marked by parallel ridges/grooves.

14. Crustal Movement on Ganymede • One look at the distribution of dark terrain on Ganymede provides convincing evidence that sections of crust have moved around. • Maybe more like arctic ice rafts than plate tectonics, but there are many parallels.

15. Callisto • Jupiter has four planetary-sized moons first seen by Galileo and easily visible in binoculars.

16. Callisto • The outermost Galilean moon, Callisto, is a stark contrast to Ganymede. • Despite being a near twin in size and density it shows no signs of surface activity.

17. Callisto • The outermost Galilean moon, Callisto, is a stark contrast to Ganymede. • There is evidence, from the gravitational deflection of spacecraft flying by Callisto that the interior is not differentiated!! → slow formation.

18. Callisto • Eroded craters point to ice sublimation.

19. Callisto • Ancient big impacts may have released mantle slush.

20. Io and Geological Activity • Io, being similar in size to the Earth's Moon, might be expected to be a geologically dead world.

21. The Galilean Satellites • Jupiter has four planetary-sized moons first seen by Galileo and easily visible in binoculars.

22. Io and Geological Activity • It turns out to be the most volcanically active world in the Solar System.

23. Io and Geological Activity • It turns out to be the most volcanically active world in the Solar System. • No impact craters! • Coloration from Sulfur and sulfur compounds. • Density = 3.0 g/cm3 • mostly rock • formed in a “warm location”? • ices baked away?

27. Io's “Atmosphere” • The volcanic activity produces a continuously escaping tenuous atmosphere of sulfur and sodium near Io, and a “torus” of this material around Jupiter.

28. Heating Io Internally – Tidal Stretching • Io has an elliptical orbit due to tugs from the other large Galilean satellites. • The solid body of Io experiences significant, regular tidal distortion as a result (the orbit takes just under 2 days)

29. Heating Io Internally – Tidal Stretching • The tidal stretching heats the interior of Io significantly, so much so that volcanism is rampant.

30. Europa and Tidal Heating • Europa is the next Galilean satellite out from Jupiter • Craters are rare on Europa as well • tidal heating is much weaker – greater distance / slower orbit • Europa, however has an icy surface – easier to melt.

31. Europa and Tidal Heating • Europa is the next Galilean satellite out from Jupiter • Craters are rare on Europa as well • tidal heating is much weaker – greater distance / slower orbit • Europa, however has an icy surface – easier to melt.

32. Europa and Tidal Heating • Europa also has a density close to 3.0 g/cc. • The outer layer of ice is the top of a true frozen-over “ocean” about 100 kilometers deep. • Weak tidal heating combined with radioactive decay keep Europa warm enough keep the ocean liquid below a few kilometers of icy crust. • Liquid water in the outer solar system!!!

33. Europa and Tidal Heating • Europa also has a density close to 3.0 g/cc. • The outer layer of ice is the top of a true frozen-over “ocean” about 100 kilometers deep. • Weak tidal heating combined with radioactive decay keep Europa warm enough keep the ocean liquid below a few kilometers of icy crust. • Liquid water in the outer solar system!!!

34. Europa as an Abode for Life • Europa's ocean is likely habitable if life formed or was delivered there. • Interestingly, it is now thought that life on Earth may have originated near submerged volcanic vents. • The most primitive life forms on Earth, the extremophiles, thrive in extreme environments – e.g. boiling water.

35. Europa as an Abode for Life • Europa's ocean is likely habitable if life formed there. • Interestingly, it is now thought that life on Earth may have originated near submerged volcanic vents. • The most primitive life forms on Earth thrive in extreme environments – e.g. boiling water.

36. Exploring Europa's Ocean • A few decades from now?