9.2 Jupiter's Galilean Moons
The amount of tidal heating is just right for life.
Does Europa have an ocean?
It's covered in an icy shell.
Europa's exterior is bright, white, and ice covered.
It is very smooth and has a few features only.
There are some faint ridge lines, giant cracks in the ice, looking like spiderwebs.
Little craters = surface is repaved very recently because liquid water comes out and freeze a new layer.
It has a metallic core, rocky interior, a water layer, and then ice surface.
The outer layers are actually: ice, soft warmer ice going through convection, and liquid water ocean beneath.
Evidence for liquid ocean:
Lack of impact craters. It means that it's erased easily, by water.
Another evidence: chaotic terrain.
They are like ice packs crisscrossed across the planet.
They are slushy ocean that froze, and then separated, so they are cracked and stuff looking like jigsaw puzzle.
There's also ridges on the planet, and there is evidence that suggests liquid water hushed out from below some of these ridges.
Galileo spacecraft detected a magnetic filed near Europa.
Because moons seldom have magnetic fields, this was weird.
It is because it is so close to Jupiter, and Jupiter has a strong magnetic field.
Consequently, the two planets pass through a magnetic current.
This current can pass through because salty ocean can conduct electricity. Therefore, this is evidence for a salty ocean under the icy crust.
If we tally up the evidence for an ocean on Europa, we can list the following:
• Calculations show that tidal heating can supply enough heat to keep most of Europa’s ice melted beneath a solid ice crust.
• The relatively small number of craters implies that the moon’s surface is young, perhaps only a few tens of millions of years old, indicating that it has
been recently repaved.
• Various features on the surface (chaotic and flooded terrain) suggest that liquid water sometimes wells up from below. • Europa has a magnetic field that is likely caused by currents produced in something that conducts electricity—like a salty ocean—as Jupiter’s magnetic
NASA is trying to send an orbiter to Europa with instruments that can prove the ocean idea.
They want to see if Europa will bulge a lot. If the core is liquid, the planet should be very stretchy and bulge towards Jupiter a lot!
Currently they thin Europa's crust is 20 to 25 km thick and the water layer is 80 to 170 km.
Could Europa have life?
summarizing the case for life on Europa:
1. There is indirect evidence for a liquid water ocean.
2. We expect the elements needed for life to be present in that ocean and on its floor.
3. There are possible energy sources to support life, but the total available energy is small compared to the energy available for life on Earth.
Taken together, there seems to be a good probability of life. But there doesn't seem to be enough energy for the development of complex sea creatures. We can
only find out for sure if we go there.
Earth had energy because in the water there was hot volcanic vents.
We don't know if it has volcanic activities inside. But it is possible, and the tidal heating, and radioactive decay etc should give it enough energy to melt some rocks
to create energy for an origin of life.
The problem is to find energy to sustain life: On Earth we have sunlight and other dead organisms, but that's not the case on Europa.
5 times farther means 25 times weaker sunlight.
If there is energy to sustain life, it is from the high energy particles trapped in Jupiter's magnetic field. They have enough energy to break up molecules when it his
a surface, and produce chemical reactions that produce energy.
Lastly, some of the potassium contained in the rocky material that makes up the moon will dissolve in to the the ocean and then we get energy from natural decay of
Could other moons of Jupiter have life?
Third from Jupiter, largest moon in the solar system.
Hard, brittle ice surface. Has both young and old surfaces, separated by sharp boundaries.
Some young areas and some old areas. The young areas were created from water eruptions which happened because of internal heat, so "waterly lava" which
The grooves were from tectonic stress that stretched the icy crust.
Galileo spacecraft went to the area and found two things:
1. It has it's own magnetic field, generated within the moon, indicating a molten convecting ocre like earth's outer core.
2. The magnetic field varies wit