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When and who discovered Jovian moons?
1610: Galileo discovered four objects
Moons of Saturn, Uranus and Neptune soon followed
differ enormously in size composition, density and atmospheres
Ganymede and Titan are larger than Mercury
What are some features of Jovian Moons?
orbit parent planet in same rotational direct and around their equators
likely formed in place with rest of solar system
some orbit at include angles and retrograde their parent planet (likely captured objects from early solar system)
Triton (Neptune’s largest moon) likely captured by releasing a satellite of triton and being dragged through Neptune atmosphere
Synchronous rotation (like moon with earth due to tidal friction slowing rotational rate)
What is the composition of Jovian moons?
mixture of rock and ice in the outer solar system
decrease in density from their planets (like planets from sun)
Jupiter has densest moons due to higher abundance of ice
What energy is there for life on Jovian Moons?
Tidal sources are main source of energy (tidal heating)
Io is extreme case with most volcanic activity in solar system
How does Io, Europa and Ganymede compare orbits?
1:2:4:
every 4 orbits of IO, Europa orbits 2, Ganymede orbits 1
Is life possible on jupiter’s moons?
Io: too many volcanoes, no liquid water
Europa: maybe right amout of tidal heating for a subsurface ocean, covered in smooth ice from cyrovolcanism, thin ice crust with subsurface ocean on top of rocky interior with iron core
What evidence is there for Europa’s oceans?
All strong evidence for global subsurface salt water ocean
some mechanisms in repaving cratering on surface; cyrovolcanism
Chaotic terrain on the surface is similar to frozen arctic ice pack, where ice is frozen into the ocean
Measurements of Europa’s changing magnetic field indicate it is produced by a salty, conductive ocean of water interacting with jupiter’s magnetic field
What life is possible in Europa’s oceans?
likely has medium and organic molecules for life
Energy is third requirement for life and is scant
tidal heating could have similar effects to deep-sea vents on earth
only energy for small, localized communities
photosynthesis only possible for life 10s of meters from the surface
reactions with Jupiter’s magnetic field might enrich ice with energy-rich hydrogen and oxygen
What features does Ganymede have?
partially active surface with young and old regions based on cratering
largest moon in solar system
magnetic field (like Europa) from molten core and Jupiter
maybe global subsurface ocean
High-pressure forms of ice beneath ice blocking energy transfer from rock
Life possible but limited and deep
What features does Callisto have?
farthest and most cratered
rock and ice
fluctuating magnetic field
maybe global subsurface ocean
not in resonance and has little tidal heating
heat from radioactive decay, with thick, icy exterior shell
ocean may be kept fluid through salts and ammonia
What features does Titan have?
appreciable atmosphere (nitrogen: 90% vs Earth’s 77%, little to no oxygen, carbon dioxide, methane, etc)
second largest satellite in solar system
similar composiiton and density to Callisto (rock, ice)
atmospheric pressure 1.6x earth
frozen surface
What is the origin of Titan’s atmosphere?
result of icy ammonia evaporating, loses hydrogen and leaves nitrogen atmosphere
methane evaporating react with UV forming hydrocarbons
Methane should run out unless from a source
Maybe evaporating pools of liquid methane
What is Titan’s singular atmosphere?
slightly smaller than Ganymede
compositon leads to atmosphere (methane ice sublimates at lower temp than water ice)
Titan is only methane ice moon vs. other water ice moons
Cometary impact energy: comets speed relative to their distance from sun, faster when closer
Slower impacts, therefore didn’t destroy the atmosphere
What is the cassini-huygens mission?
smalled lander to first non-earth moon
shows titan’s geography is similar to earth (coastal regions, rivers but carrying methane and ethane)
shows noble gasses in atmosphere implying from outgassing not impacts
points to cryovolcanism
Is life possible on Titan?
energy for life is scarce
liquids are not water (ethane and methane instead)
slow life from less energetic reactions
energy could be extracted from organic compound in atmosphere
shape hints at subsurface ocean which could support life
life would be challenging but not impossible
What are features of Enceladus?
geologically active
tiger stripes indicate warmer portions of crust with pressure and stress and cracking, spray salty water into space
young ice
ongoing volcanism
silica particles that only form at high temps prove energy for life
What are features of Triton (Neptune)?
captured by neptune
cantalope terrain, limited cratering
young surface
source of internal heat is unknown
possibly a subsurface ocean
What is chemical disequilibrium?
necessary for condition of life
chemical energy move into chemical equilibrium so chemical reactions cease
natural on Earth
on any geologically active world
What are redox reactions?
electric charge is shuffled between elements
involves an electron donor and electron acceptor
backbone of most energy (photosynthesis)
process could provide energy for life in subsurface coeans
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