Transcript Life in the Ocean?

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
Io’s Volcanoes
The most volcanically active world in the solar system.
Europa: An ice-covered world
Europa: Heated by tidal friction
Europa
– Tidal heating, similar to IO but
weaker
– Young cracked water ice crust
perhaps only a few kilometers
thick
– Thought to have a warm ocean
of salty liquid water below its
crust.
– 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-Crust
Ocean
..
.
Hydrogen-Carbon
compounds likely:
Amino acids
First New Ocean
Life in the
Ocean?
Since Balboa
Life in the
Ocean?
Conditions are
consistent with the
.
presence
of
volcanic
.
vents .(black smokers)
at bottoms of ocean.
Life could have
developed there.
Life in the
Ocean?
Complex life?
Probably requires oxygen
High energy
particles from
Jupiter
Collisions
disassociate
water
H
H
O
Hydrogen lost to space,
oxygen absorbed by ice
H
O
H
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 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
Callisto
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)
(yellow)
(green)
(blue)
nothing
planets close to stars will have
synchronized rotations
planets far from stars will have
synchronized rotations
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)
(yellow)
nothing
planets close to stars will have
synchronized rotations
Life beneath the surface of Europa would
most likely obtain energy from
(red)
(yellow)
(blue)
(green)
the Sun
Jupiter
radioactivity
tidal heating
Life beneath the surface of Europa would
most likely obtain energy from
(re)
(yellow)
(blue)
(green)
the Sun
Jupiter
radioactivity
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?
• Io
X
• Europa
Very active volcanically.
Hostile environment
?
• Ganymede
Subsurface saline
ocean, hydrothermal
vents?
? Subsurface saline
ocean? hydrothermal
vents?
• Callisto
saline
?? Subsurface
ocean?