1. Europa and Life
5 October 2016

2. The Galilean Satellites of Jupiter
In 1609, Galileo used his recently invented telescope to look at Jupiter
He saw 4 small ‘stars’ moving with the planet
He concluded that they were moons orbiting Jupiter, like planets circling the Sun
Although he called them the ‘Medician’ stars in honor of his patron, Duke Cosimo of Medici, we know them as the Galilean satellites

3. If we remove water density increasesIo
3.57 g/cc
Ganymede
1.94 g/cc
Europa
2.97 g/cc
Callisto
1.86 g/cc
If we remove water density increases
Orbital Resonance
Io Europa Ganymede Callisto
Tidal Heating

9. Europa: general characteristics
Size:
R = ±0.5 km
Composition:
silicate rock and H2O ice
Interior:
water-ice crust and probably, subsurface ocean, and an iron–nickel core
Surface:
temperature averages about 110 K (−160 °C) at the equator and only 50 K (−220 °C) at the poles -> water ice acts like rock
Atmosphere:
Tenuous, O2
Size:
R = ±0.5 km
Composition:
silicate rock and H2O ice
Interior:
water-ice crust and probably, subsurface ocean, and an iron–nickel core
Surface:
temperature averages about 110 K (−160 °C) at the equator and only 50 K (−220 °C) at the poles -> water ice acts like rock
Atmosphere:
Tenuous, O2
Slightly smaller than the Moon, Europa is primarily made of silicate rock and has a water-ice crust and probably an iron–nickel core.
tenuous atmosphere composed primarily of oxygen

12. Warm ice..or..liquid water?
Europa: interior
Warm ice..or..liquid water?
or some combination?

13. Europa: surface
hypothesis proposes that heat from tidal flexing causes the ocean to remain liquid and drives geological activity similar to plate tectonics
the smoothest surface of any known solid object in the Solar System
Europa's most striking surface features are a series of dark streaks crisscrossing the entire globe, called lineae

16. Conamara Chaos
mysterious “brown gunk” is probably sea salt baked by radiation -> means underlying ocean is in direct contact with rock and enriched with potentially life-nurturing amounts of minerals
produced by the disruption of the icy crust of Europa

18. Compare to California’s San Andreas Fault
Europa
Astypalaea Linea
San Andreas Fault

19. “cycloid” ridges
daily fracturing?
(120 miles across)

20. Lenticulae – “freckles” – convective upwelling of warm buoyant ice

22. Icebergs?
(25 miles across)

23. Tilted ice blocks look like the Arctic Ocean too…

24. Europa’s surface shows few craters

25. Tyre multi-ring impact structure
Few large impact craters: ->
Suggests 60 Myr surface age.
A couple of multi-ringed impacts: -> Penetrated 20 km thick ice!

26. Few large impact craters: ->
Suggests 60 Myr surface age.
A couple of multi-ringed impacts: -> Penetrated 20 km thick ice!

27. Europa: ocean and atmosphere
surface pressure of Europa's atmosphere is 10−12 atm
tenuous ionosphere
H2, O2, O that escapes Europa's gravity form a gas torus in the vicinity of Europa's orbit around Jupiter -> feeds Jupiter’s magnetospheric plasma
A lot of water
periodically occurring plumes of water 200 km high
ionosphere (an upper-atmospheric layer of charged particles) around Europa created by solar radiation and energetic particles from Jupiter's magnetosphere

28. Europa: potential habitability
one of the top locations in the Solar System in terms of potential habitability and the possibility of hosting life
Life could exist in its under-ice ocean, perhaps subsisting in an environment similar to Earth's deep-ocean hydrothermal vents.[

30. Discussion Topics
What experiments would you take to Europa to find the water and search for life? Talk with those near you and make a short list.
Would you land on Europa? Why or why not?
Where would you land?

31. Summary
Many of the icy bodies in the outer Solar System are internally differentiated
Thanks to tidal heating, Europa and Enceladus may have a liquid ocean between the icy crust and the rocky core
Warm rock in contact with water heats it: this starts convection. Hot water can emerge from cracks in the surface: this provides chemical energy for possible life
If Earth life arose at hydrothermal vents, it could happen there, too. Also light can reach into the cracks, possibly allowing temporary photosynthesis