Feb. 16 th Feb. 23 rd Classification atmosphere, composition, distance, rotation, revolution? Phases vs. Epicycles (position with respect to sun) Terrestrial 1. Mercury (moon like) Rotation 58.65 days Day = 176 days Revolution 88 days 2/3 ratio tidal braking with eccentric orbit (58.646 vs 87.969) Axial tilt 0 degrees Size radius 2439km Composition silicate rocks and Fe/Ni core Density about 5.4g/cc Information from density Mantle thin (639km) silicate rocks (Basalt) Core thick (1800km) Fe/Ni solid Heat of location, early collision Tectonically inactive Craters Scarps possibly due to craters or shrinkage Hummocky terrain Atmosphere none Temperature and size Surface Temperature 100 to 700 degrees Kelvin 1% of Earth no liquid core, slow rotation, possibly residual 2. Venus (Earth like?) Rotation 243 days retrograde Early collision Day = 117 days Revolution 224.7 days
Axial tilt 177.4 degrees (retrograde 2.6 degrees) Size radius 6052km Composition silicate rocks and Fe/Ni core Density about 5.25g/cc Information from density and analogy with Earth Mantle silicate rocks Core Fe/Ni solid Tectonically active Two highland regions (based on radar mapping) Magellan Spacecraft Ishtar and Aphrodite (8% of surface) Volcanic Shield volcanoes/domes Sampled by Venera - pictures Lightning may indicate activity/increases in SO2 Small number of craters Volcanic activity and atmosphere Difference from Earth due to Water/Crustal Thickness? Atmosphere 96% CO2 3.5% Nitrogen, trace water vapor and others From spectrum and space probes Clouds sulfuric acid droplets 30km to 60km reflectivity = brightness Dense 100 times Earth Surface Temperature uniformly 750 degrees Kelvin Greenhouse effect Weak - slow rotation Earth Moon (Luna) Done as Analogs 4. Mars (Earth like) Rotation 24.6 hours Revolution 687 days Axial tilt 24 degrees Size radius 3398km Composition silicate rocks and Fe/Ni core
Density about 3.94g/cc Information from density and Mars Global Surveyer Mantle silicate rocks (Basalt) Core Fe/Ni solid Tectonically active Enormous volcanoes (Olympus Mons 26km tall) Trenches (Valles Marineris) 5000km long,100km wide, 10km deep Craters Low tectonic activity Atmosphere 1%of Earth (CO2 and Nitrogen) Water present but rare Obvious channels due to water flow Lower Pressure from: Early Collision, Low Gravity Polar Caps south = dry ice south = water ice elevation Surface Temperature average 218 degrees Kelvin No planet-wide magnetic field Satellites (Demos, Phobos) 20 km across not particularly spherical Influences on Planet Character Mass and Radius Internal Activity Sunlight Water Content Biological Processes Jovian 5. Jupiter (Jupiter like) Rotation 9.9 hours Significant equatorial bulge Revolution 11.86 years
Axial tilt 3 degrees Size radius 71,492km Composition theoretical considerations Density 1.3 g/cc 10,000km deep liquid Hydrogen eventually metallic liquid hydrogen core = two time size of Earth (silicate and iron) HOT = 30,000 K emits more radiation than it receives Rising heat leads to convection Atmosphere Hydrogen, helium and hydrogen compounds Methane CH4, Ammonia NH3 and Water H2O Clouds particles of water ice and ammonia compounds Convection currents Winds = up to 300km/hr Rising gas between belts swirled into vortexes Great Red Spot Convection in liquid metallic hydrogen = strongest magnetic field in solar system (20 times Earth) account for radius and 20,000 times stronger Ring one, thin ring of rock dust, must be replenished Satellites (roughly 62 at current count) Galilean Satellites Io Radius 1,821km density 3.5 strong and changing orbit due to Jupiter and Europa = internal friction Volcanic plumes and lava Sulfur is major component = yellow red Europa Radius 1,565km density 2.99 cracked egg crust of ice, lines of mineral-rich water No craters friction heat keeps interior Liquid allows surface to flow Ganymede Radius 2,634km density 1.94
craters like our moon but probably ice not enough craters = some are removed May have iron/rocky core Callisto Radius 2,403km density 1.85 craters of ice may have ocean beneath icy crust Other Satellites are a few to a hundred km and some have orbits at high angles to others 6. Saturn (Jupiter like) Rotation 10.66 hours Significant equatorial bulge Revolution 29.5 years Axial tilt 26.7 degrees Size radius 60,268km Composition theoretical considerations Density 0.69 g/cc Less than water Similar to Jupiter (mostly hydrogen and helium) Spectra bear this out emits more radiation than it receives condensation and gravitational energy of He drops Atmosphere Hydrogen, helium and hydrogen compounds Methane CH4, Ammonia NH3 and Water H2O Clouds particles of water ice and ammonia compounds Less dramatic than Jupiter due to colder temperature Ammonia gas freezes into particles making lower Clouds indistinct Convection in liquid metallic hydrogen Rings 100,000km wide, few 100 m thick Doppler shift = different velocities inner and outer Obeys Kepler s third law Spectra = mostly water ice but different colors suggest variable composition
possibly carbon compounds Gaps gravitational effects of local moons Cassini gap = Enceladus Shepherd satellites Short-lived, replenished from moons Roche Limit approx 2.44 planetary radii Satellites (roughly 31 at current count) Titan Radius 2,575km density 1.88 g/cc has its own atmosphere mostly N hydrocarbon oceans chemical calculations methane rain Other Satellites are 750 km or less but have similar densities. 7. Uranus (Jupiter like) Rotation 17.24 hours Revolution 84 years Axial tilt 97.9 degrees Equator roughly perpendicular to orbit Moons orbit equatorially Early impact Size radius 25,559km Composition theoretical considerations Density = 1.32 g/cc More heavies than Jupiter but no Fe/Silicates Light and Abundant = water? Fits size of bulge Possible rocky core (small) Atmosphere Hydrogen, Methane CH4, Water Blue color, methane absorbs the red Uneven heating due to tilt may explain lack of clouds Convection in liquid water? Also tilted but well off from spin axis. Rings narrow, thin rings of small particles Color suggests not ice(carbon or organic molecules) Narrowness may be due to shepherding satellites Satellites (roughly 27 at current count)
5 large/others small, all under 800km Miranda Odd structure and geography Early impact/gravity restored pieces 8. Neptune (Jupiter like) Rotation 16.11 hours Revolution 165 years Axial tilt 29.56 degrees Size radius 24,764km Composition theoretical considerations Density = 1.64 g/cc Inferred to be similar to Uranus Atmosphere Hydrogen, Methane CH4, Water Blue color, methane absorbs the red Clouds frozen methane Emits more radiation than receives Convection currents = cloud bands Wind Speed in excess of 2000km/hr Present Ring very narrow, sometimes clumped Shepherd Satellites Satellites (roughly 13 at current count) Triton huge and backward orbit! And highly tilted! Size = 1,353km Atmosphere present Geysers from interior but crater marked Dwarf Planets Pluto Density = 2.1 g/cc Tenuous atmosphere Mostly Nitrogen and Carbon monoxide Small gravity offset by extreme cold (40K) Moon (Charon) orbit = 6.4 days Dozens of presumably icy object a few hundred km in
diameter orbit at similar distance from the sun as Pluto Others are bigger (Quaoar 1300km diameter) Asteroids Small rocky bodies 2-4 a.u. from sun Combined mass < 1/1000 mass of Earth 1000km to 1km or less irregularly shaped carbonaceous, rocky, metallic Differentiation argues for destroyed planet. Fragments of Planetesimals Gaps in the asteroid belt due to Jupiter s gravity Kirkwood Gaps Apollo asteroids (700 ish) Earth collisions roughly every 10,000 years Meteorites shooting star = meteoroid Heated by friction with atmosphere (10-40km/sec) Most vaporized but bits that remain meteorite Rocky, Iron, Rocky-Iron Small, rounded rocky chunks = chondrules Rapidly melted and cooled 4.5 billion years old Carbonaceous chondrules Carbonaceous matter including amino acids Comets Nucleus and tail Ice and gases (dirty snowball) Giotto (European Space Agency) Density = 0.2 g/cc fluffy Spectra of Tail = CO2, CO and Water broken into O2 and H2
Tail = radiation pressure (solar wind) Always points away from sun Fate is to be dissipated by sun over time Kuiper Belt In the disk of the solar nebula from Neptune s orbit to our beyond Pluto Ort Cloud Swarm of comet nuclei far beyond the orbit of Pluto Planetesimals tossed out by planetary gravitational Interactions Spherical shell out to some 150,000 a.u. Theories on Formation Origin of Solar System Interstellar Clouds Few light years in diameter Hydrogen 71%, Helium 27% tiny traces of C, O, and Si Interstellar dust particles Large molecules to microns Silicates, iron compounds, carbon compounds and water frozen into ice Spectral lines of light passing through Similar to composition of Sun Rotating collapse caused flattening Condensation in the Solar Nebula Few million years flattened disk with central bulge 200 a.u. diameter inner parts hot, outer parts cold Condensation Gas cools below critical temp. Fe @ 1300K Silicates @ 1200K
Highest vaporization temps. condense first Inner belt (Fe, silicates) Outer belt (ice) Little water, hydrogen, etc in inner part due to ease of vaporization. Accretion and Planetesimals Tiny particles due to condensation stick together Collisions causes growth to mm or km Rocky-iron inner belt Rocky-iron-ice outer belt Planets Collisions could be destructive or constructive Faster in outer belt because of the abundance of water With sufficient growth, gravity can attract and hold an atmosphere (hydrogen abundance = size) Collisions release heat, melt planets and allow differentiation by mass. Moons Planetesimals orbiting planets Scaled down version of planet formation Final Stages Rain of planetesimals causing craters Impacts Formation of our moon. Odd rotation of Venus Odd rotation of Uranus Some survived to make moons, asteroids, comets Atmospheres Inner planets by outgassing volcanically or impacts Outer planets by gravitational capture Cleaning up Sun s heat drive flow of gas outward Solar System to Scale Giant Impacts E =1/2mv 2 Extinctions
Possible Planets beyond our solar system! In 2008-373 (most quite large) Gravitational effect on local star Doppler wobble Pulls star side to side Gravitational lensing Transits affect light intensity Direct observation 10km asteroid = several billion nuclear weapons