Extraterrestrial Volcanism

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1 Extraterrestrial Volcanism What does it take to create volcanic activity? How do different planetary conditions influence volcanism? Venus Volcanism in our solar system. Io Europa

2 Mercury Venus Earth/Moon Rocky Planets Mars Gaseous Planets Jupiter Saturn Uranus Neptune

3 Requirements for Volcanism Source of Heat Primordial Heat Radiogenic Heat Tidal Heat (Io) Solar Heat (Triton) Europa Something to Melt Io

4 Earth s Moon The Moon originated by an impact between Earth and a Mars-sized body, hence it is made mostly of material that was once in Earth s mantle. The Moon's surface is currently geologically dead. No atmosphere at this time, little in the past.

Although seismic evidence and detailed observations of its orbit and

5 Lunar Interior The Moon underwent limited differentiation but has a comparatively small core. Although seismic evidence and detailed observations of its orbit and rotation suggest there is still some molten material in its interior, no magma has reached its surface recently.

Two distinct terrain types: Surface of the Moon Light, cratered highlands made of anorthosite, a plutonic igneous rock, around four billion years old.

6 Two distinct terrain types: Surface of the Moon Light, cratered highlands made of anorthosite, a plutonic igneous rock, around four billion years old. Light highlands Darker, blotchy mare basins of low viscosity basalt flows that are very extensive, with flow fronts meters high. Three distinct phases of volcanic activity. Mare basins No obvious volcanoes; some rare volcanic domes.

7 Contrasts between Terrestrial and Lunar Volcanism Lunar volcanism is extinct; most is older than 3 billion years. No linear patterns of volcanic mountain chains on the moon (i.e., no arcs or hot spot trails). No evidence for lunar plate tectonics. Nearly no evidence for anything other than basaltic volcanism on the moon. Most lunar basalt is in larger craters or the thin crust of the nearside. Basalt deposits are flat and very broad. Dominantly fissure eruptions. Lunar gravity is one-sixth that of Earth. Very little water in the basalts. Little explosivity in eruptions. Ejecta widely spread, so no build-up of cones. No subduction/water to form continental crust.

8 Unusual Volcanic Features Certain volcanic features are cryptic: Flow fronts Wrinkle ridges Sinuous rilles Meandering channels from a few meters to several km wide, several hundred km long. May be the result of collapse of lava tubes and thermal erosion. Also some vestiges of explosive activity, probably driven by the last remaining CO 2, forming widespread but thin dark deposits; no cinder cones seen.

9 Sinuous Rilles Giant lava tubes or channels?

10 Dark Mantling Deposits May indicate some explosive volcanism.

11 Lunar Pyroclastic Deposits Approximately 100 identified Identifiable by dark deposits From very deep sources, perhaps down to 400 km Richer in volatiles than other lunar basalts Age of deposits generally greater than 3.5 billion years

12 Venus Similar in size and density to Earth, but closer to Sun; water couldn t form oceans. Covered in clouds of CO 2. Surface temp 500 o C and pressure 90 bars. Exceeds both Earth and Mars in number of preserved volcanic landforms, over 22,000 on just 25% of the surface area. Most abundant are small shields (2-8 km diameter) with small central crater, in large fields or colles.

13 Venusian Volcanism Long lava flows, km long. Long lava channels, or canali. One is the longest single channel in the solar system at 6800 km (Earth s Nile is 6497 km). Calderas, paterae, typically km in diameter, usually in sites of prior extensive eruptions.

14 Venusian Volcanic Features Lava Flows

15 Venusian Volcanic Features Sapas Mons, a volcano 400 km across and 1.5 km high

16 Venusian Volcanic Features The cone volcanoes in this cluster are about 2 km in diameter and 200 meters high. Sacajawea Patera is an elliptical caldera measuring 260 by 175 km.

17 Venusian Volcanic Features This cluster of four overlapping domes average about 25 kilometers in diameter with maximum heights of 750 meters. These features can be interpreted as viscous eruptions of lava coming from a vent on the relatively level ground

18 Jupiter s Moons (the Galilean Satelites) Io Europa Ganymede Callisto

19 Io Ganymede Europa Callisto

The innermost of Jupiter s four Galilean satellites. Io Size and density comparable to Earth s Moon. Only body outside Earth with confirmed active volcanism, with 100 active centers identified.

20 The innermost of Jupiter s four Galilean satellites. Io Size and density comparable to Earth s Moon. Only body outside Earth with confirmed active volcanism, with 100 active centers identified. 500 km 3 /yr of lava erupted, (8-15 km 3 /yr on Earth); over 300 times as much lava despite having only 1.5% the mass of Earth. Few craters- a young surface as a result of persistent volcanism.

21 Io Active plumes that rise hundreds of km above surface. Eruption temps much higher than those on Earth, 1300 o C or more. Ultramafic? Possible sulfur lava flows from remobilized deposits What causes heating?

22 Io Radioactive decay is not sufficient to heat Io s interior. Tidal forces- from orbiting Jupiter- create gravitational kneading that keeps its combined metal and silicate interior hot and partially molten. Visible spots on left correspond to hot spots on image at right

23 Pillan Patera 140 km - high plume Io s Volcanic Plumes Prometheus 75 km - high plume

24 Io s Volcanic Features 7th Orbit 10th Orbit Note new dark spot, 400 kilometers (249 miles) in diameter, (which is roughly the size of Arizona), surrounds Pillan Patera volcanic center. Six months elapsed time, Galileo spacecraft.

Io s Volcanic Features The reddish, white and black areas are surface deposits, consisting of mixtures of salts, sulfur and sublimate deposits of

25 Io s Volcanic Features The reddish, white and black areas are surface deposits, consisting of mixtures of salts, sulfur and sublimate deposits of volcanic origin. Many of the black spots in these pictures are associated with craters of possible volcanic origin. The smallest features are 10 km across.

Model for Sulfur Volcanism on Io Sulfur is ejected as S2, as confirmed by Hubble in 1999.

26 Model for Sulfur Volcanism on Io Sulfur is ejected as S2, as confirmed by Hubble in Upon landing, this sulfur rearranges into S3 and S4, producing a reddish color. Eventually these join to form conventional S8 rings with the ordinary pale yellow sulfur color.

27 Io s Volcanic Features The central feature has been named Loki Patera. The large dark area might be a lake of liquid sulfur with a raft of solid sulfur inside.

28 Io to Europa

29 Europa Cryovolcanism One of the Galilean moons of Jupiter (total of 63 known moons). Similar in size to Earth s Moon. Surface covered by water ice, very few craters.

30 Europa s Surface Red linear features are cracks and ridges caused by Jupiter s tides. Blocky chaotic terrain of broken ice blocks. Red material is a non-ice contaminant (salts from ocean below?). Few impact craters - young surface.

31 Europa Blocks which are thought to have broken apart and "rafted" into new positions. Evidence for liquid ocean beneath,

32 Europa s Surface Dark spots (lenticulae = freckles) are possible evidence for warmer ice from below moving upwards. Each spot is about 10 km across.

33 Flows on Europa 186 km Possible ice flow cutting across a ridge, perhaps erupted as a viscous, glacial mass.

34 Europa Two current models for Europa s interior. Combined with the geologic data, the presence of a magnetic field leads scientists to believe an ocean is most likely present within Europa today.

35 Io Ganymede Europa Callisto

36 Ganymede Dark areas: old, heavily cratered. Light areas: younger, tectonically deformed. Bright spots: recent impact craters and ejecta.

37 Ganymede Tectonics Ejectafilled impact crater Double impact crater Tectonic rifting of impact crater

38 Ancient Surface Flow on Ganymede

39 Europa Few craters. Young surface. Active icy tectonics and flows. Ganymede Some cratering Range of ages Early icy tectonics, similar to Europa. Callisto Cratered Old surface Eroded, covered by dark layer.

The Galilean Satellites. Jupiter has four planetary-sized moons first seen by Galileo and easily visible in binoculars.

The Galilean Satellites. Jupiter has four planetary-sized moons first seen by Galileo and easily visible in binoculars. 1 The Galilean Satellites Jupiter has four planetary-sized moons first seen by Galileo and easily visible in binoculars. 2 The Galilean Satellites Jupiter has four planetary-sized moons first seen by Galileo