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Cryovolcanism

GLY 424/524

April 12, 2002

What is it?

• Eruption of “ice” onto a planetary surface

• May be composed of– Water ice

– Methane ice

– Ammonia ice

– Probably others

Known Locations

• Triton– Neptune’s moon

– Voyager observed active methane geysers

– Driven by solar energy

• Europa– Jupiter’s second moon

– Young surface

– Albedo, temps consistent with water ice• But probably not pure water ice

Voyager view of Europa

Europa

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Voyager seesEuropa Europa Characteristics

• Jupiter’s second moon (between Io andGannymede)

• High albedo

• Few impact craters

• Smooth surface with dark bands

Europa Characteristics

• Diameter = 3138 km– Smallest of the gallilean satellites

– Slightly smaller than our Moon

– 6th largest satellite in the solar system

• Gravity = 1.31 m/s2

• Density = 3010 kg/m3

– ρwater = 1000 kg/m3

• Silicate core

• Water mantle & lithosphere

Europa’sInterior

Surface

• Few impact craters– Young surface

– <30 Myr?

• <1 km relief– Weak surface (150°C)

• Relatively high albedo– ~0.64

• Consistent with water ice

Two Terrains

• dark– Mottled, brown or gray

– Hilly, hummocky

• light– Smooth plains

– Criss-crossed with dark bands

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F.o.v. ~240 km16°S, 196°W

Galileo sees Europa Geologic Units: Plains

• Smooth– Generally dark

– Circular to irregular in planform outline

– volcanic

• Ridged– Tectonic ridges

– Among oldest features on Europa

• Undifferentiated– Depends on image resolution

Dark bandsF.o.v. ~2000 km

Geologic Units: Chaos

• Platy, knobby, fractured, and rotated blocksof crust

• Interpreted to be surface crust disrupted byinternal activity– Evidence for internal heat source?

– Mantle (water ice?) plumes?

Chaos terrain: 30 km x 50 km

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Geologic Units: Bands

• Linear, curved or wedge-shaped zones

• Contrasting albedo (brightness)

• Margins may look like bounding ramps orridges

• Band interiors commonly higher thanadjacent terrain

• Magma-filled fractures?

Bands360 x 770 km

Geologic Units: Ridges

• Straight or curved

• Single or double

• More complex designs– Curved

– Branching

• Interpretations– Spatter ridges

– Filled fractures

– Linear diapirs

F.o.v. ~1260 kmDark bandsSmooth plains

Thera and Thrace MaculaF.o.v. ~675 km

F.o.v. ~20 km

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F.o.v.~15 km “The Puddle”

~ 3km across