Outline of my three lectures:

1.Brief introduction of planetary geology of the solar system.

2.Tectonics of rocky planets in the inner solar system (Mercury, Venus, and ).

3.Tectonics of icy satellites in the outer solar system (Europa and Enceladus). LectureLecture 1:1: IntroductionIntroduction toto planetaryplanetary geologygeology ofof thethe solarsolar systemsystem (a(a grandgrand fieldfield trip)trip) Picture is ~1 billion light years = 1025 - 1026 m; large voids in space  The largest scale “picture” ever taken.  Each point is a galaxy like our Milky Way, clumped together as ‘superclusters‘.  The universe is “bubble” about 15 billion years old, and it is mostly empty space. 1021 m Our Sun orbits about the center of the Milky Way once every 250 to 300 million years. The small white circle around the Sun has a radius of 1600 Our Sun and ly. the solar system

The majority of the stars you can see with your eye lie within this small area.

OurOur SolarSolar SystemSystem Where did the solar-system material come from? Galactic recycling: star formation and explosion created and dispersed primitive light elements (H and He) and newly formed heavy elements.  The universe was created by Big Bang.

 The universe is expanding in all directions.

 Using the observed expanding rate, the age of the universe is estimated to be ~15 billion years old.

 Although the universe is expanding in all directions, gravity operates at local scales and pulls things together to make galaxies and stars.  Big Bang produces hydrogen and helium.

 Gravity pulls gas clouds together to form galaxies and stars.

 Nuclear fusion occurs when pressure and temperature exceed critical point in the center of a gas cloud, the star: light-weight atomic nuclei smashed together to form heavier nuclei.

 When dying, a star explodes and scatters elements they produced into space. Born in clouds of gas and dust produced by early star formation and explosion

Explosion Nuclear of star fusion scattering creating elements heavier produced elements by start than formation hydrogen process and helium Origin of Elements  Material making up our solar system was recycled from early star formation and destruction.

 98% of solar system material are helium and hydrogen, and 2% are everything else, which contributes to the formation of the rocky planets.

98% mass of our solar system Inner Solar System: Four rocky/terrestrial planets

Mercury Mars Venus Earth Ourter Solar System: Four rocky/terrestrial planets Rocky Planets

Mercury Some basic facts about Mercury:  Surface temperature: 100 K at night and 700 K during the day.  Extremely thin atmosphere containing H, He, Na, and K.  Weak magnetic field but is capable of deflecting the solar wind.  Highly cratered surface with local water ice.  Large iron core. Vaporizing sulfur left stable minerals bounding empty air holes. The spongy rock is weak and crumbled by its own weight or during impact-induced shaking, forming the pitted depressions. Formation of central peak ring

Close up view Creating a crater depression is similar to splashing water with a water drop.

(1) Europa (icy satellite of Jupiter): 5 km.

(2) Mars: 8-10 km.

(3) Moon: 15-20 km.

(4) Venus: Craters with diameters < 10 km are scarce, due to its thick atmosphere; dominantly complex craters with central uplifts and multi-ring crater basins.

(5) Earth: 2-4 km.

(6) Mercury: 10 km. D = 1.2 km Age = 50,000 years Impact object: Iron meteorite

A decrease in the rate of neutron release an indication of the presence of water ice. This is because abundant hydrogen atoms in the ice layer prevent the neutrons from escaping into space.  Radar-bright materials in north pole were postulated as water ice in permanently shadowed regions.

 The MESSENGER spacecraft confirms water ice.

 Total volume: 100 billion to 1 trillion tons at both poles; ice could locally be > 20 m thick. Relative size of core, mantle and crust of Earth and Mercury large core for Mercury In summary, Mercury has  A very thin atmosphere.  A dipole magnetic field (1.1% that of Earth's magnetic field).  A heavily cratered surface.  An extreme high daily temperature variation (100-700 K).  A large metallic core. Venus  Dense carbon dioxide atmosphere.  High surface temperature (>750 K) due to greenhouse effect.  No water!!  No active magnetic field!!  Reverse spinning direction!! A shaded relief map of Venus constructed from radar altimeter data collected by the Magellan orbiter. Ishtar Terra from the polar view (my favorite feature as it is so similar to Tibet!!)

Plateau

Rifts

Cronae Basins (plural of Crona) Plateaus on Venus and Earth

Tibetan plateau on Earth

Ishtar Terra on Venus In summary, Venus has  A dense carbon-dioxide atmosphere.  No active magnetic field (and perhaps never had a one??).  Moderately cratered surface with an age < 800 Ma.  Current surface shows no water. Mars

 A thin atmosphere (0.6% of Earth’s atmosphere Pressure)  No active magnetic field  Had magnetic field and a dense atmosphere in the first 500 Ma of its history

Dichotomy Boundary Northern low lands (3-4 km below mean elevation)

Southern low lands (1-2 km above mean elevation) Dichotomy Thinner crust (32 km) and a similar old age to the Boundary southern highlands; cratered surface is buried

Thicker crust with many craters (58 km) Impact origin for the dichotomy boundary Mode-1 mantle convection for the origin of the dichotomy boundary Utopia Basin

Isidis Basin

Hella Basin Argyre Basin

Alba Patera (6.8 km) Montes (three sisters!) (13.9 km)

Olympus Mons (21.2 km)

Valles Marineris

Outflow channels much like those on Earth

Magnetic field existed only in its first 300-400 Ma history

Phoenix lander

Mars Science Laboratory (Curiosity) Mars Science Laboratory (MSL) is a robotic space probe mission to Mars launched on November 26, 2011 and landed Curiosity in Crater on August 6, 2012

Spirit & Opportunity c. 2004 Pathfinder c. 1997 MSL “Curiosity” Launch: Nov. 25, 2011 Landing: Aug 6, 2012 62 MSL site at Gale crater (selected 10/18/2011) Landing and science: http://mars.jpl.nasa.gov/msl/news/whatsnew/index.c http://www.youtube.com/wat fm?FuseAction=ShowNews&NewsID=1164 ch?v=0m56hJbESqs

MSL mission science: http://www.nasa.gov/multimedia/videogallery/ index.html?collection_id=18895&media_id=18416 173 Mission updates at: http://mars.jpl.nasa.gov/msl/news/whatsnew/ 63 Context of Curiosity Landing Site in Gale Crater, with Ellipse. The central mount is known as Mt. Sharp. Its formation involves first water and then wind!

Powerful wind erosion

Clifford and Parker (2001 Icarus 154, 40-79) delineated locations of several proposed shorelines. Carr and Head (2003 Journal of Geophysical Research, 108, No. E5, 5042) presented more compelling evidence. Yes, beach on Mars!!!

Where did the water go?

North Pole Pole Mainly water ice, but covered by ~1 m (north pole) and 8-m (south pole) thick dry ice.

North Pole South Pole

Frozen water everywhere: “Recurrent slope lineae” (RSL) on Mars: incrementally grow during warm seasons and fade in cold seasons Asteroid Belt Asteroid Belt 79 Ceres (940 km) Pallas (570 km) Vesta (525 km) Hygeia (444 km) Ida + Dactyl (moons: common)

20 km

0.2 km 10 km Eros

Itokawa Vesta, Ceres and Earth’s moon the Moon with sizes shown to scale

Ceres Vesta

Lead scientist for the Dawn Mission: My former graduate student Jen Scully Prof. Chris at UCLA worked on buried ice and formation of gullies. Digital Topography of Vesta (north and south polar regions 30 km Vesta Ceres: Heavily cratered surface Digital topography in polar projection Digital topography in cylindrical projection Paradox: lack of water ice at the surface despite its low density requires the presence of ice. Surface of Ceres  Bright spots, commonly associated with clay, are some form of salt containing magnesium sulfate hexahydrite (MgSO4·6H2O)

Jupiter Warm zones are light and whereas dark zones are cool and falling Jupiter has a powerful magnetic field

Major findings by the Galileo spacecraft (1989-2003): a.Io's volcanism. b.liquid ocean under icy surface of Europa, Ganymede and Callisto. c.Ganymede’s magnetic field! d.Established global structure of Jupiter's magnetosphere.

Galilean moons of Jupiter Rocky Satellite Icy Satellites Galilean moons of Jupiter Rocky Satellite Icy Satellites

Io and “pipe tectonics” for early Earth Very young lava, some of which are still “warm” as detected by infrared cam era. 2 6 September, 2 0 1 3 | Vol. 5 0 1 | Predictions of the Heat Pipe Model: (1)A cold and thick lithosphere was developed as a result of frequent volcanic eruptions that advected surface materials downwards. (2)Declining heat sources over time led to an abrupt transition to plate tectonics a rapid decrease in heat-pipe volcanism. Snapshots of the temperature field for two-dimensional models of mantle convection from Moore and Webb (2013) with different “internal-heating

Rayleigh number”, RaH. In the model, melt extracts to and spreads over the surface instantaneously, while the cold lithosphere advects downwards to conserve mass.

Moore and Webb (2013 Nature) Lithospheric temperature as a function of downward advection rate (0.1 mm/yr, 1.0 mm/yr, and 10 mm/yr) and lithosphere thickness (120 km, 150 km, and 180 km)

Very low temp at a great depth when recycling rate is high (10 mm/yr) Moore and Webb (2013 Nature) Relative fraction of heat transport and dimensionless maximum lithospheric stress as functions of the dimensionless internal heating rate (αHD2/k).

Volcanic heat-pipe transport dominates at higher internal heating rates.

At very high heating rates (Io), lithospheric thickness variations lead to larger stresses.

Moore and Webb (2013 Nature) Internal heat production, surface conductive heat transport and surface volcanic heat transport as functions of dimensionless time in a model with a finite yield stress.

“Plate breaking At the time when the events” volcanic heat flow becomes small compared with the conductive heat flow, the plate breaks and the entire lithosphere is replaced in a sudden overturn.

Moore and Webb (2013 Nature) Thermal boundary layer overturns shown in the simulation, interpreted as initiation of subduction in the 2- D model

Storm in Saturn’s atmosphere

Cassini spacecraft. Image What drives the powerful magnetic field of Jupiter and Saturn? Helium Rain Second possible explanation:

1.Compositional gradient inside Saturn with a more heavy element content inside. 2.This leads to layered convection.

Compositional gradient

Second-largest moon in the Solar System, mean radius = 2576 km. Only moon with a nitrogen-rich dense atmosphere in the Solar System.

What do you see? Other geologic features: what do you see here and what does it say about the environment of Titan? Surface age of less than a few million years.

The tiger stripes are 2 km wide and 0.5 km deep. Gas Giants Trans- Neptune Objects ( belt and Oort Cloud)

Ice Giants Methane in Uranus’ (and Neptune’s) atmosphere makes  Rocky core (possible look blue because of methane’s with a metallic absorption property. component), water and methane ice mantle, and a gas envelope.

 Atmosphere.

 Magnetosphere.

 Rotation axis tilted 97o with a retrograde spin.

 Icy moons with tidally induced tectonics.

Uranus' Odd Orbital Inclination • 84-year orbital period Poles

• Alternate between 42 years of sunlight and 42 years of darkness. What caused the retrograde spinning: probably a big impact event during the initial formation state of the solar system Magnetosphere: non-coaxial with spinning axis. The angle between the geographic and magnetic north is about 60o. Convection and rotation are decoupled. Uranus has 27 known natural satellites, among them 5 are major spherical moons; Voyager 2 was only able to image the southern hemispheres of these moons (why??) Miranda Ariel Umriel Titania Oberon

Influence of tides increase towards Uranus, expecting more tectonic activities and thus younger ages of the surfaces. Almost true, but not exact! Miranda (472 km in diameter): “grooved” terrain was caused by upwelling of warm ice and surface extension

Ariel (1,158 km in diameter)

1. Ariel is the brightest moon in the Uranian system.

2. A network of interconnected rift valleys 100s km long and reach depths of 10 km. Axial tile angle = 28o, similar to that for Earth (23o) and Mars (25o)  The densest gas giant.  Structure: similar to Uranus  Atmosphere: similar but more stormy.  Magnetosphere: similarly odd as that of Uranus.  Its moons: only one that has a significant size.  Its relationship to Kuiper belt.

Atmosphere:

Similar in composition and temperature profile to Uranus (its surface is warmer than that of Uranus).

Stronger storms.

A trace amount of methane causes its blueness.

Large “black spot” similar to the “red spot” on Jupiter. Magnetosphere:

A stronger quadrupole field than dipole field.

Spinning axis and magnetic north has a 47o angle.

Neptune’s moons:

Triton: largest with R = 1353 km; retrograde orbit; possibly captured from Kuiper belt.

Proteus: largest irregularly shaped moon in solar system, 218 km x 208 km x 201 km.

Nereid: third largest moon R = 170 km.

The rest of the moons are all smaller than 100 km in radius and irregularly shaped. Eruption centers: dark streaks are leftover dusts after gas and ice being Surface features of Triton: removed. 40% of Triton's surface imaged by Voyager 2.

Active geysers erupting gas and “ice lava”.

Ridges, troughs, furrows, hollows, plateaus, icy plains and few craters.

Reflective southern cap covered by frozen nitrogen and methane.  “Cantaloupe terrain”: an organized cellular pattern of noncircular dimples.

 Resemble salt domes exposed on Earth (Gulf of Mexico).

 Mean separation of the cells is 47 km, which requires an ice crust ∼20 km thick.

Salt domes (block dots) in the Gulf of Mexico A vertical cross section of salt structures across the gulf Jan Hendrik Oort (1900-1992) hypothesized in 1950 that a spherical cloud of predominantly icy planetesimals may lie roughly 50,000 AU, or nearly a light-year, from the Sun.

• InnerThis image Oord is copyright clouds by the Leidenare Observatory distributed on a disk. • Outer Oord clouds are in a spherical shell Our solar system

Unknown until 1992 Kenneth Essex Edgeworth, (1880 - 1972), Irish

Gerrit Pieter Kuiper, (1905 - 1973), Dutch - American Jane Luu and David Jewett discovered the first real Kuiper Belt Object: 1992 QB1, which led to the demise of Pluto as a planet, as it is merely one of many Kuiper Belt objects (KBO) The objects listed below include everything outside Neptune, some of which may belong to the Oord Cloud Closest Approach July 14, 2015 Size and Density

• Pluto’s diameter resolved to 2370 km.

• Diameter larger than previous estimates, indicating lower density.

• Charon’s diameter is 1208 km.

A

B

400 km 120 km Central Regio Two materials on Pluto’s surface: (1) light but strong water ice, and (2) denser but viscous nitrogen fluid that flows like glaciers. Valley Glaciers

126 km Water Ice Mountains Tartarus Dorsa

106 km Pits Canyons

Layered Atmosphere Kuiper Belt consists of Trans-Neptune objects including Pluto  > 900 objects with sizes larger than 1,000 km may exist in the inner Oort cloud.

 Some inner Oort cloud objects could rival the size of Mars or even Earth, but they are too faint to be detected.