The Galilean Satellites: January 1610 Galileo’s sketches JPL Solar System Simulator Revealing Europa’sOcean Robert T . Pappalardo Jet Propulsion Laboratory California Institute of Technology

Mosaic by Ted Stryk

 2012 California Institute of Technology. Government sponsorship acknowledged.

Oceans Come and Go, and Return Again Pioneer 10 Views Europa (1973)

 1971–1977: Early satellite oceans

Arcturus proposed from thermal-compositional models [Lewis, Consolmagno, Fanale]

 Late 1979–1983: Tidal heating might maintain oceans, but convection of overlilying i ce mi ihtfght freeze oceans [Cassen, Peale, Reynolds, Squyres]

Neptune  1989: Tidal heating of Europa’s Pioneer 10 JPL Eyes on the Solar System ice could be sufficient to maintain a conductive ice shell above a global  Scan by imaging photopolarimeter ocean [Ojakangas & Stevenson]  Dec. 3, 1973, ~200 km/pixel [Reynolds & Cassen., 1979]

Voyagers View Europa (1979) Galileo Orbital Tour (1996-1999)

 Few large impact craters - young surface or “relaxation”? End of Galileo Europa Mission  Mottled terrain 31 Dec. 1999 - internal activity or only impacts?  Bright, lineated plains - crustal mobility [Schenk & Seyfert, 1980; Schenk & McKinnon, 1989]

12 Europa Encounters 9 “Non-Targetted” Encounters

Voyager 1 (20 km/pixel) Voyager 2 (2 km/pixel)

1 Galileo’s First Views of Europa (1996)

 Pits (endogenic?)  Spots (volcanic?)  Age brightening  Nonsynchronous rotation  Crustal mobility

Galileo Imaging Team (1996) Color composite by Paul Geissler

Europa’s Surface Europa’s Interior

ridged plains chaotic terrain

Europa’s Magnetic Interactions Ridges

Art by Michael Carroll

Mosaic by Ryan Sicilia

2 Ridge Formation Models Bands

shear heating

[courtesy L. Prockter]

Impacts Surface Composition

Pwyll Tyre

Non-ice candidates: - Sulfate salts

(MgSO4 • nH2O) - Sulfuric acid

(H2SO4 • nH2O)

Lenticulae (Freckles) Icy Lava Lamp?

T = 100 K cold, stiff ice

warm, flowing ice

Mosaic by Ryan Sicilia T = 260 K [courtesy A. Barr]

3 Icebergs? Chaos

[Schmidt et al., 2011] 270 m

Europa: Ingredients for Life? Understanding Europa’s Habitability: Key Issues  Water: More than 2x all of Earth’s oceans  Essential elements: From formation and impacts • Ocean: Existence, extent, and salinity  Chemical energy: Potentially from above and below • Ice Shell: Existence and nature of water  Stability: Variable, but “simmering” for 4 billion years within or beneath, and nature of surface- ice-oceaoceaecagen exchange

• Composition: Distribution and chemistry of key compounds and the links to ocean composition

• Geology: Characteristics and formation of surface features, including sites of recent or current activity “Black smoker” on Earth’s ocean floor Woods Hole Oceanographic Institution

Looking Forward: Europa Clipper

Operations Concept: Science: - 32 low altitude flybys of Europa from Jupiter Clipper orbit over 2.3 years Objective Enhanced w Recon Ocean  - Detailed investigation of globally distributed Ice Shell  regions of Europa Composition  - Simple repetitive science operations Geology  - Landing site reconnaisance capability Recon 

Langmuir Probe Magnetometer (LP) (x2) Payload: (Mag)

Clipper Recon Camera Instrument Neutral Mass (Recon) Enh w Recon Spectrometer (NMS) IPR Thermal Imager (Thermal) Floor SWIRS Gravity Science Antenna (GS) TI Technical Margins NMS Shortwave Infrared Spectrometer 39% 40% 75% MAG (SWIRS) LP Mass Power Data Baseline Ice Penetrating GS Radar(IPR) Recon Topographical Cost: $2.0B Imager (TI) Thermal $FY15, Phases A-E Excl LV Copyright 2012 California Institute of Technology. Government sponsorship acknowledged. 10/16/2012 Pre-Decisional — For Planning and Discussion Purposes Only 23

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