11 Planetary Exploration Travel to exotic locations

11 Jupiter’s four “Galilean” moons Similar size to our moon Visible with binoculars:

11 Io: Innermost large moon Similar in size to the Moon. Intensely volcanically active! (40 times as active as Earth) Hundreds of active volcanos, plumes hundreds of miles high Why? This was unexpected. –Scientists expected to see something like our moon –Io is too small for internal heat and too far from the sun for solar heat

11 Io Glowing in the Dark... Galileo images show glowing gases, hot volcanos, in Jupiter’s shadow Volcanic glow suggests volcanos are too hot to be “ordinary” basalt magma

11 Tidal Heating of Io Where does the energy come from? Tides distort Io when closer to Jupiter: surface moves 100 meters every day Continually changing shape heats interior

11 Eruptions

11 Learning about the volcanos What kind of volcanos are they? How hot are they? What are they made of? What can they tell us about volcanos on Earth?

11 Links to the Earth There have been huge eruptions on Earth that have never been seen by humans, but similar events are frequent on Io.

11 Zooming in on Jupiter and Io Jupiter and its moons from a backyard telescope (1,000,000 miles across)

11 Zooming in on Jupiter and Io Best view of Jupiter from an Earth- based telescope (100,000 miles across)

11 Zooming in on Jupiter and Io Jupiter and Io from Hubble (60,000 miles across)

11 Zooming in on Jupiter and Io Io against Jupiter, from Galileo (2200 miles across)

11 Zooming in on Jupiter and Io Io volcanos Prometheus and Culann (450 miles across)

11 Zooming in on Jupiter and Io Prometheus lava flow, Io (50 miles across)

11 Zooming in on Jupiter and Io Edge of Prometheus lava flow, Io (6 miles across)

11 Tvashtar, November 1999 Fire Fountains seen by Galileo SSI From Hawaii

11 And again by Galileo SSI in February, 2000 Also seen from the ground Also seen from the ground

11 What we’ve learned Volcanos are hotter than Earth’s volcanos (up to 2700 F vs F): like volcanos early in Earth’s history Eruptions much like terrestrial ones (but bigger): fire fountains, lava flows, lava lakes

11 Europa: Abode of life? Little known before Galileo... Icy, fractured, surface

11 Zooming in on Europa:

x 140 km

11 32 x 42 km

11 Eroded appearance at highest resolution Few impact craters 1.7 x 4 km

11 Surface layer has fractured and separated: floating on ocean, or slush?

11 Craters subdued, rare: young(?), soft surface

11 Ocean on Europa? Jury is still out – but many scientists agree Galileo data shows evidence for thin rigid crust over soft interior, but can’t tell if interior is liquid, or slushy ice Surface is probably very young, currently active, but possibly as old as 1 b.y., which would probably rule out ocean

11 Comparative planetology

11 Surface Processes Io –Volcanism (endogenic) –No craters (young surface) Europa –Tectonics (endogenic) –Cryovolcanism (endogenic) –Few craters (young surface) Ganymede –Tectonics (endogenic) –Some craters (older surface) Callisto –Mostly Craters (very old surface)