Enceladus & Life
23 February 2016
Io
Europa
Enceladus
All these moons are heated by tides that stretch and press them
Enceladus
•
•
•
Size: 513.2 × 502.8 × 496.6 km
Composition: ice and rock
Jets – source of Saturn’s E-ring
Habitability:
• Enceladus ejects plumes of salt
water + grains of silica-rich sand,
nitrogen (in ammonia), nutrients
and organic molecules
• This indicates that hydrothermal
activity—an energy source—
may be at work in Enceladus's
subsurface ocean.
• The underground warm water
provides a possible location
for life, perhaps similar to that
found under the ice cover of
Antarctic lakes.
Enceladus Surface
• Voyager images (1980,1981) showed both
heavily cratered and smooth regions
• Cassini saw great fractures in the south, called
‘tiger stripes’
• These cracks probably extend down to water
reservoirs, because ice grains and vapor jet
out of them
• These are the warmest parts of Enceladus
surface
Enceladus Interior
• Differentiated: Rocky core at the center,
surrounded by ice mantle, with water oceans
and seas, covered by a cold, icy crust
• Some unknown plumbing brings the water
under pressure to the surface, where it freezes
and shoots out like an ice cannon
• Thus the jets can sample the interior without
needing to land and drill down
ISS observation of jets
“Tiger stripes”
Enceladus… the next Io???
Stellar occultation
-> gas in plumes
Magnetic perturbation
-> local ionization
Cryovolcanism
Enceladus’ Cryovolcanic Style
• Enceladus jets: water
escapes at ~200 kg/sec!
• Io’s eruptions don’t
reach escape velocity!
• Why the difference?
Tiger Stripes
IR images
-> Temperature:
Tiger Stripes
are warm
Source of heat?
• Tidal heating
• Radioactive
heating
• Chemistry
(ammonia)
Tiger Stripes close-up
Even closer!
Discussion Topic: Talk with those near
you
• What types of experiments would you carry to
Enceladus to look for life?
Latest Enceladus Images from
Cassini
14 October 2015
Cassini’s
Last
Photo
Future Search for Enceladus Life
• First: Where is the water?
– At South Pole tiger stripes
– 1-50km deep
• Getting to Enceladus is not easy, it is a long trip, requires
multiple rocket burns to reach it and to land softly
• How to reach water
– Fly through plumes
– Land safely near the plume (not easy because the surface is
rough) and then drill (hot brick?)
• Staged approach
– Saturn orbiter with multiple flybys provides detailed maps; then
an Enceladus orbiter and lander; finally, mobility to explore with
a rover
• Tests for life
– Microscopy, culture a sample, labeled nutrients, identify life
molecules: amino acids, polypeptides, polysaccharides, lipids,
nucleic acids and DNA
Summary
•
•
•
•
Enceladus is heated by tides
Water erupts in jets to form a giant plume
This shows a salty, underground ocean
Enceladus has all the requirements for life
– Liquid water, biogenic elements from rocks and
meteorites, energy from sunlight and geothermal
• Search for life by flying through and by drilling
down to the ocean