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 world

Europa: Heated by tidal friction

Europa –Tidal heating, –Tidal heating, similar to IO but weaker water ice crust –Young cracked water ice crust perhaps only a few kilometers thick warm ocean of salty liquid water –Thought to have a warm ocean of salty liquid water below its crust. –life?

– Icebergs

ice cliffs

Grooves & channels

Glaciers?

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-CrustOcean.. Life in the Ocean?.. Hydrogen-Carbon compounds 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

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 crust outer warm ice mantle inner silicate mantle metallic 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

“Classic” cratered iceball. No tidal heating - no orbital resonances. But it has magnetic field! This is not understood.

Callisto Scarp 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? IoIo EuropaEuropa GanymedeGanymede CallistoCallisto X Very active volcanically. Hostile environment Subsurface saline ocean, hydrothermal vents? ? Subsurface saline ocean? hydrothermal vents? ? Subsurface saline ocean? ??