Known Locations Voyager view of Europa · Cryovolcanism GLY 424/524 ... Known Locations • Triton...
Transcript of Known Locations Voyager view of Europa · Cryovolcanism GLY 424/524 ... Known Locations • Triton...
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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