Homework 7 will be posted shortly

YU55

If it had struck land, it might have caused a magnitude seven earthquake and left a city-sized crater.

If it has struck the ocean, it would have raised a large tsunami.

Jupiter’s Galilean Satellite’s

Orbital resonances among Galilean Satellite’s

Io’s Volcanoes

The most volcanically active world in the solar system.

Io

Europa: An ice-covered worldEuropa: An ice-covered world

Europa: Heated by tidal frictionEuropa: Heated by tidal friction

EuropaEuropa

– Tidal heating,Tidal heating, similar to IO but weaker

– Young cracked water ice crustwater ice crust perhaps only a few kilometers thick

– Thought to have a warm ocean warm ocean of salty liquid waterof salty liquid water below its crust.

– life?life?

– Icebergs

ice cliffs

Grooves

&

channels

Glaciers?

Earth: arctic ocean

Earth: arctic ocean

Europa’s interior warmed by tidal heating.Internal structure derived from measurements taken

by spacecraft in the Jovian system.

Salty - Europa has a magnetic field

Sub-CrustSub-CrustOceanOcean ....

Life in the Ocean?

..

Hydrogen-Carboncompounds likely:

Amino acids

First New Ocean

Since Balboa

......

Conditions are consistent with the

presence of volcanic vents (black smokers) at bottoms of ocean.

Life could have developed there.

Life in the Ocean?

Life in the Ocean?

Complex life? Probably requires oxygen High energy

particles from Jupiter

H

O

H

Collisions disassociate

water

H

H

O

Hydrogen lost to space, oxygen absorbed by ice

On timescale of several million years, oxygen moves

through ice to ocean

Missions to Europa

http://www.jpl.nasa.gov/europaorbiter/

Ganymede

Ice-covered moon

Craters and pressure ridges

Ganymede• Largest moon in the solar system• Clear evidence of geological activity • Tidal heating expected - but is it enough?

Ganymede

Wrinkles due to tectonic movement in ice crust in (distant) past - possible water deep below?

Model of Ganymede's interior:

cold rigid ice crustouter warm ice mantleinner silicate mantlemetallic core.

Ganymede• Cratering

– Dark areas: cratering upon cratering several byr old– Bright areas: far fewer craters and grooves– Explanation: “lava” (i.e., water) eruptions followed by freezing

• Ocean?– Magnetic field convecting core– Part of magnetic field varies with Jupiter’s rotation electrically

conducting interior (brine?)– Salts found on the surface

• Heat source– Less tidal heating than Europa (larger distance from Jupiter)– Large mass more radioactivity– Much less heat than in Europa thick crust (>150 km?) Much harder to prove the existence of life, never mind finding it

Callisto

Callisto• “Classic” cratered iceball.

• No tidal heating - no orbital resonances.

• But it has magnetic field! This is not understood.

CallistoScarp close up

Possible water deep?

Callisto• Cratering

– Heavily cratered everywhere no water gushing to the surface

• Gravity– Undifferentiated: mix of ice and rock throughout

• Induced magnetic field– Exists underground ocean? Not clear.

• Heat source?– Does not participate in the tidal resonance– Radioactive decay: only possibility for heating of

interior

Given our discussion of tidal synchronization of the rotation and orbital periods, what might this say about planets and stars?

(red) nothing(yellow) planets close to stars

will have synchronized rotations

(green) planets far from stars will have synchronized rotations

(blue) it will depend upon the composition of

the planet

Given our discussion of tidal synchronization of the rotation and orbital periods, what might this say about planets and stars?

(red) nothing(yellow) planets close to stars

will have synchronized rotations

Life beneath the surface of Europa would most likely obtain energy from

(red) the Sun (yellow) Jupiter(blue) radioactivity (green) tidal heating

Life beneath the surface of Europa would most likely obtain energy from

(re) the Sun (yellow) Jupiter(blue) radioactivity (green) tidal heating

Life in the subsurface ocean of Europa will most likely consist of

(red) creatures similar to seals and penguins which enter the ocean through holes in the icy crust

(yellow) plants on the ocean floor(green) simple single-celled organisms(blue)fish and other complex aquatic

organisms

Life in the subsurface ocean of Europa will most likely consist of

(red) creatures similar to seals and penguins which enter the ocean through holes in the icy crust

(yellow) plants on the ocean floor(green) simple single-celled organisms(blue)fish and other complex aquatic

organisms

Life on Galilean Moons?Life on Galilean Moons?

• IoIo

• EuropaEuropa

• GanymedeGanymede

• CallistoCallisto

XX Very active volcanically. Very active volcanically. Hostile environmentHostile environment

Subsurface saline Subsurface saline ocean, hydrothermal ocean, hydrothermal vents?vents?

??

Subsurface saline Subsurface saline ocean? hydrothermal ocean? hydrothermal vents?vents?

??

Subsurface saline Subsurface saline ocean? ocean?

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