Life in Jovian Moons Notes

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

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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


1. some mechanisms in repaving cratering on surface; cyrovolcanism
2. Chaotic terrain on the surface is similar to frozen arctic ice pack, where ice is frozen into the ocean
3. 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