Slide 1Slide 2Slide 3Slide 4QuestionsSlide 6Slide 7Slide 8Slide 9Slide 10Greenhouse EffectSlide 12The Interior of the EarthSlide 14Slide 15TidesSlide 17Slide 18Slide 19Determining rotation rate of a planetVenusSlide 22Anomalous rotation of VenusSlide 24Olympus MonsMarsSlide 27Slide 28Slide 29Slide 30Slide 31Differential RotationSlide 33Slide 34Slide 35Slide 36Slide 37Slide 38Slide 39Slide 40Slide 41Info for the TestBring a #2 pencil.No electronic devices: No cell phones, headphones, etc.No books, notes, etc.No hats.Grades will be posted on the Mastering Astronomy website.Two Kinds of Planets"Terrestrial"Mercury, Venus,Earth, Mars"Jovian"Jupiter, Saturn, Uranus, NeptuneDistance from Sun?Size?Composition?Density?Rotation Rate?Number of moons?Rings?Heavy or light elements?Two Kinds of Planets"Terrestrial"Mercury, Venus,Earth, Mars"Jovian"Jupiter, Saturn, Uranus, NeptuneClose to the SunSmallMostly RockyHigh Density Slow Rotation (1 - 243 days)Few MoonsNo RingsHeavy Elements (Fe, Si, C, O)Far from the SunLargeMostly GaseousLow Density Fast Rotation (0.41 - 0.72 days)Many MoonsRingsLight Elements (H, He)Origin of PlutoNow known to be just one of the largest of a class of objects in the outer reaches of the Solar System:The Kuiper Belt ObjectsQuestionsWhat are some of the smaller objects (or debris) found in the solar system?Comets, asteroids, meteoroidsWhat is the main reason that we study these smaller objects? (What information do they contain that the planets and moons do not?)Solar system debris is unevolved => gives direct evidence of conditions during solar system formation!Nucleus: ~10 km ball of ice, dustComa: cloud of gas and dust around nucleus (~106 km across)Tail: can have both ion and dust tails (~108 km long). Always points away from Sun.Comet StructureSolar System FormationOur solar system started out as a giant cloud of cold gas that collapsed under its own gravity.So, why is our solar system flat?Conservation of angular momentum!What role did dust play in the formation of our solar system?Condensation theory: 1) Dust grains act as "condensation nuclei": gas atoms stick to them => growth of first clumps of matter. Also radiate heat => help to cool gas => faster gravitational collapse.What term describes the process by which smaller particles collide and stick together to form larger clumps?Condensation theory: 1) Dust grains act as "condensation nuclei": gas atoms stick to them => growth of first clumps of matter. Also radiate heat => help to cool gas => faster gravitational collapse. 2) Accretion: Clumps collide and stick => larger clumps. Eventually, small-moon sized objects: "planetesimals". 3) Gravity-enhanced accretion: objects now have significant gravity. Mutual attraction accelerates accretion. Bigger objects grow faster => a few planet-sized objects.Greenhouse EffectWhat is the greenhouse effect and how does it differ on Earth and on Venus?Runaway Greenhouse Effect on VenusThe Interior of the EarthHow does temperature vary as we get closer to the core of the Earth?What about density?Earth's Internal StructureTemperature and density increase with increasing depth.How do we obtain information about the structure of the Earth's interior?Like all waves, seismic waves bend when they encounter changes in density. If density change is gradual, wave path is curved.S-waves are unable to travel in liquid.Measurement of seismic waves gives info about density of Earth's interior and which layers are solid/molten.TidesWhat causes the tides?When are the highest (and lowest) tides seen?The Lunar Surface● Large, dark featureless areas: "maria" or "seas". More recent lava flows.● Lighter areas at higher elevation: "highlands".● Many craters (due to meteorite impacts). Only important source of erosion!● Highlands have 10x the crater density of maria => Highlands are older.mariahighlandsImpact Theory Early in Solar System, when many large planetesimals around, a Mars-sized object hit the forming Earth, ejecting material from the mantle which went into orbit around Earth and coalesced to form Moon. Computer simulations suggest this is plausible.MercuryMass = 0.055 MEarth Radius = 0.38 REarth Surface Temp: 100 - 700 KAverage distance from Sun =.39 AUMoonlike: Surface craters, no atmosphere (escaped long ago due to high surface temp & low mass)Orbital period = 88 daysRotation period = 59 days (Exactly 2/3 of Mercury’s year!)Composite image from Mariner 10 1970sDetermining rotation rate of a planetUse reflected radio waves to determine line ofsight doppler shifts.VenusThick clouds prevent viewing of surface. (UV Image)High temperatures and pressures, acidic gases, make it difficult to land anything on surface.Led to much speculation.How did we get info about surface?"Radar Mapping" technique measures altitude space probetime for signal to return tells you the altitude of surface feature.Planet SurfaceAnomalous rotation of Venus•Extremely slow - Venutian solar day longer than Venutian year!•Retrograde - Sun rises in the west and sets in the east!•Most likely due to a collision during solar system formationProperties of the PlanetsWhich planet has the largest known volcano in the solar system?Olympus MonsLargest known volcano in Solar System – 3X the height of Everest!MarsWhat is the main reason that many scientists think Mars may have once harbored life?What is the most likely origin of the two moons of Mars?Evidence for Past Surface Water"runoff channels" or dry rivers"outflow channels" teardrop "islands" in outflow channels standing water erosion in craters?Mars' Moons Phobos and DeimosPhobos: 28 x 20 kmDeimos: 16 x 10 kmProperties similar to asteroids. They are probably asteroids captured into orbit by Mars' gravity.Discovery of NeptuneNeptune predicted to exist because of irregularities in Uranus' orbit.Neptune discovered in 1845 by Johann Galle.Gravitational perturbation of Uranus’ orbit by unseen planet led to discovery of Neptune! Kepler’s and Newton’s laws in action & Nice example of how the scientific method worksJupiter's BandsLighter-colored "zones" and darker-colored "belts".Shadow of a moonGreat Red SpotBeltZone- Zones and belts are Jupiter's high and low pressure systems, respectively.- They mark a convection cycle. - Jupiter's rapid rotation stretches them horizontally around the entire planet.- Temperature difference between zones and belts => different chemistry =>