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 Mars). 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 Very 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) Tharsis Montes (three sisters!) Elysium Mons (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 Gale 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 South 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 Russell 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 (aHD2/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.