Enceladus & Life 23 February 2016

Io Europa Enceladus All these moons are heated by tides that stretch and press them

Size: × × 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

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???

Magnetic perturbation -> local ionization Stellar occultation -> gas in plumes

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