Solar System

Chapter

Planet Groupings• Terrestrial Planets– Inner

• Mercury• Venus

– Earth– Outer

• Mars

• Gas Giants– Naked Eye

• Jupiter• Saturn

– Discovered with Telescopes• Uranus• Neptune

Terrestrial Planets

Mercury

Page 135-141

Mercury

• Visible Only a few hours before sunrise or after sunset.

• Sometimes the brightest object in the sky– Dark surface– Close to sun

• Temperature Extremes– Thin, Transient atmosphere (H2, He, Na,K,O2)

– Solar day is 176 earth days long

Mercury Surface

• Like Lunar landscape–Many impact craters

• No maria–Plains

• Scarps– Long Cliffs–Cooled, contracted, collapsed nonuniformily

Caloris Basin

• Caloris = “heat”• Closest area to the sun– Near Terminator• Huge impact area– Twice Size of Texas

• Small craters filled with lava• Opposite side jumbled hilly surface– Energy focused by the planet like a lens

By the NumbersStatistic Mercury Earth

Avg Distance from Sun .387 AU 1.0 AU

Eccentricity .21 .017

Orbital Speed 47.9 km/s 29.79 km/s

Period of Revolution (Yr) 88.0 Earth Days 365.26 Days

Rotation (Day) 176 Earth Days 24 hours

Inclination to orbit .5o 23.5o

Radius .382 Earth radii 1

Mass .0553 Earth mass 1

Density 5430 kg/m3 5520 kg/m3

Gravity .38 Earth 1

Albedo .12 .37

Avg Temperature 350 OC, -170 OC 60 OC, -90 OC

Atmosphere Thin, Transient, H, He,Na,K,O N2,O2, CO2, H2O (vapor)

Crust

Interior Structure• Average density similar to earth– Dense interiors– 5430 kg/m3 versus 5520 kg/m3

• High Iron content– Low iron on surface– High percent from core (Earth 17%, Mercury 42%)

• Rocky Mantle• Thin crust• Earth’s Greater Volume compresses interior

Venus

Page 141-147Bright Morning or Evening Star

Goddess of LoveEarth’s Sister Planet

Comparisons• Mercury and Venus– Not much in common– Neither has a moon– Venus twice distance from sun

• Venus and Earth– Same mass– Same size– ergo: same density– Venus is 30% closer to sun than earth

Appearance

• One of the brightest objects in sky – Sun and moon brighter

• Evening or Morning Star– Higher in sky than Mercury

• Often mistaken for a UFO– Light is refracted by atmosphere– Changes color and position

• Very bright– Light colored reflective clouds

1960’s Probes

• US and Soviets sent probes– US light weight orbiters– Russians heavy landers

• Soviets – Venera 1970- 1983– Transmitted for 23 minutes in 1970– Surface Temperature 750k (900 F)– Atmospheric Pressure 90 atm (90x earth),

2700ft underwater (1/2 mile)

Atmosphere

• Content– 96% Carbon Dioxide– 4% mostly Nitrogen– Vented from inside the planet

• Clouds– Layer between 48 to 68 km– Haze 20 km above and 20 km below– Appear yellow due to presence of sulfur– Droplets of concentrated sulfuric acid

Volcanoes

• Sulfur compounds – breakdown easily, must be replenished– likely from volcanoes

• Lightening– Indicate volcanoes– Cause short lived magnetic field

Intense Greenhouse Effect• Carbon dioxide is transparent to visible light.• Most of sunlight that strikes Venus is reflected• Some strikes the surface-heats the surface• Heat energy is reflected as infrared• Carbon dioxide absorbs this infrared radiation• Atmosphere heats• Some returns to surface, some radiated to

space.• Equilibrium is reached but very hot 750 K

Surface Features

• No water – • Venusian rock quite similar to lava rock on

earth – basalt see page 144• Surface mapped by radar from orbiting probes– Flat– Volcanic plains (filled smooth with lava)– Gentle rolling hills– 2 large highland areas (continents?)

Venus surface (continued)• Northern highland – Ishtar Terra– Babylonia goddess of love– size of Australia– highest mountain – Maxwell Montes• 11km versus 9km for Mt Everest

• Largest highland area – Aphrodite Terra– Roman goddess of love– Straddles the equator– ½ size of Africa

• No plate tectonics

Craters on Venus

• 1600 Volcano craters• Fewer than 1000 impact craters• Thick atmosphere vaporizes infalling objects

Composite of Infrared Images

Retrograde Rotation• Rotation is clockwise while revolution around

sun is counterclockwise.• Tilt to the axis is 177o

• Monumental Impact flipped the planet over

Earth 23oVenus 177o

By the Numbers

Statistic Venus Earth

Avg Distance from Sun .723 AU 1.0 AU

Eccentricity .007 .017

Orbital Speed 35.0 km/s 29.79 km/s

Period of Revolution (Yr) 224.7 Earth Days 365.26 Days

Solar Rotation (Day) 116.8 Earth Days 24 hours

Inclination to orbit 177.4o 23.5o

Radius .949 Earth radii 1

Mass .815 Earth mass 1

Density 5240 kg/m3 5520 kg/m3

Gravity .91 Earth 1

Albedo .59 .37

Avg Temperature 460 OC 60 OC, -90 OC

Atmosphere 96.5% CO2 , 3.5% N2, .003 H2O N2,O2, CO2, H2O (vapor)

Solar System

Mars

Page 147-162God of War

Alien Lair

Favorite Hangout for Aliens• Christian Huygens telescopic observations– 1659– Dark surface feature– 24 hour rotation

• Giovanni Schiaparelli– 1877– 40 dark lines– Canali = channels, translated as Canals

Aliens continued• Percival Lowell– Wealthy– Built major observatory (late 19th century)– “Observed” 160 Martian canals– Speculated canals used to bring water from polar

ice caps to dry equatorial area

• War of the Worlds– Orson Welles radio broadcast– Martian invasion– Listen

Spacecraft to Mars

• Beginning in the 1970’s• Mariner Missions• Currently 3 Rovers on Mars (2 active)• Surveys• Pictures• Chemical Sampling• Planned manned missions to Mars ???

Mars Surface

• Red – rocks and dust indicating high iron oxide• Dry- dusty (dust storms and dust devils)• Broad plains• Shallow craters• Enormous inactive volcanoes• Vast canyons

Mars Surface continued• Vastitas Borealis – Northern Vastness or

Northern Lowlands• Southern Highlands– 5km higher than north– Heavily cratered– hilly plains

• Difference may be due to Plate Tectonics• Valles Marineris– Parallel to equator– 4000 km (1/5 of circumference)– 4 miles deep and 120 miles wide– Large crack that formed as planet cooled.– Like a Grand Canyon from Los Angeles to New York

Olympus Mons

• Largest Volcano in the solar system• Size of Missouri• 16 miles (26 km) high – 3x Mt Everest– Mauna Loa (highest on earth) 17 km above ocean

floor

Olympus Mons and Hawaiian Islands

Cluster of Cones

• Near Olympus Mons• Cone shaped craters• Similar cones in Iceland on Earth• Believe they were formed by water under the

surface vaporized by lava from the volcano and burst through the surface

• Compare to the holes in pancakes-

Other Evidence for water on Mars

• Polar Ice Caps– Frozen carbon dioxide on surface– Perhaps frozen water under surface

• Dried up river beds• River deltas• Sedimentation laid down by water• Water formed hematite• Recent evidence of flow

Evidence for water on Mars

• “Bubble” Cones• Polar Ice Caps– Frozen carbon dioxide on surface– Perhaps frozen water under surface

• Dried up river beds• River deltas• Sedimentation laid down by water• Water formed hematite• Recent evidence of flow

Search for Life on Mars

• No canals or cities• No structures • Viking spacecraft in 1975– Compact biological laboratory– No evidence of life– Methane – produced by life forms (cow burps)

• Meteorites from Mars on Earth– Possible bacterial life

Martian Atmosphere

• Very thin– 0.6% of earth atmospheric pressure

• 95% Carbon Dioxide– Nitrogen, Argon, trace Oxygen– Little water vapor because of low gravity

Martian Interior

• Lots of questions waiting for seismic detectors• Crust 40km thick in north/70km in south• Molten core– Less molten than earth– Once more molten

• No magnetic field, but once had magnetic field• No tectonic plate motion now

Martian Moons• Two tiny moons close to surface– Discovered in 1877– Phobos = fear– Deimos = panic

• Phobos– Larger– Potato shaped– Heavily cratered

• Deimos– Football shaped

• Captured planetesimals (rock fragments)

By the NumbersStatistic Mercury Venus Earth Mars

From Sun .387 AU .723 AU 1.0 AU 1.52

Eccentricity .21 .007 .017 .093

Orbit Speed 47.9 km/s 35.0 km/s 29.79 km/s 24.1 km/s

Revolution 88.0 Earth Days 224.7 Earth Days 365.26 Days 687 earth days

Solar Day 176 Earth Days 116.8 Earth Days 24 hours 24 hr 39m 35s

Inclination .5o 177.4o 23.5o 25.19o

Radius .382 Earth radii .949 Earth radii 1 .53 earth radii

Mass .0553 Earth mass .815 Earth mass 1 .107 earth mass

Density 5430 kg/m3 5240 kg/m3 5520 kg/m3 3950 kg/m3

Gravity .38 Earth .91 Earth 1 .38 earth

Albedo .12 .59 .37 .16

Avg Temp 350 OC, -170 OC 460 OC 60 OC, -90 OC 20 OC, -140 OC

Atmosphere Thin, Transient, H, He,Na,K,O

96.5% CO2 , 3.5% N2, .003 H2O

N2,O2, CO2, H2O (vapor)

95.3% CO2 2.7% N2, .03% H2O

Comparison of Planetary Features

• Page 160-162• Table 5-1

Planet Project• Graphic Display– Photos and information

• Written Report (+500 words)• Oral Presentation• 3 Sources– Astronomy magazine– Text book– One other- “not wiki”

• Physical description– Size, orbit, rotation, orbit– Moons– Unusual feature

• Space probes that have visited– Names, dates , what was discovered