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?