This is an old study guide that was requested by students in the Fall 2005 semester.
The Origin of the Solar System
Four Challenges
1. Patterns of Motion
2. Categorizing Planets
3. Asteroids and Comets
4. Exceptions to the Rules
Formation of the Solar System
q How do we know what the Earth’s interior is like?
q The waves generated by earthquakes (seismic waves) allow us to study the Earth’s interior revealing four layers:
o thin crust
o a mantle of hot solid silicates
o a liquid iron and nickel outer core
o inner core of solid iron and nickel
Plate Tectonics - The Earth’s crust drifts on top of the mantle.
Perhaps the continents we have today were part of a super continent (called Pangea) millions of years ago.
The Earth’s Atmosphere
q troposphere - the lowest level of Earth's atmosphere where all weather occurs78% Nitrogen, 21% Oxygen
q stratosphere - the second layer of the Earth's atmosphere where ozone can be found
q mesosphere - the third layer of the Earth's atmosphere where meteorites vaporize
q ionosphere - the fourth layer of the Earth's atmosphere kept partly ionized by solar UV radiation
Origin of the Earth’s Atmosphere:
The nitrogen (N2), carbon dioxide (CO2) and water (H2O) of our atmosphere may have come from volcanic gases vented over the Earth’s history or from evaporated remains of comets that hit Earth in its infancy. Plant life produced the oxygen (O2) by photosynthesis.
The Greenhouse Effect is the trapping of infrared radiation by an atmosphere. It helps stabilize the surface temperature for a planet.
Lunar Surface Features
q Moon craters that were created billions of years ago by asteroid impacts.
q For many craters you will see long, light streaks of pulverized rock called rays.
q You can also see lunar canyons called rilles.
Lunar Missions
q The Lunar Surveyor spacecrafts were among the first to reach the moon’s surface.
q There were 6 manned missions to the lunar surface.
q 12 Americans during the Apollo program
Maria
q The large, smooth, dark areas on the Moon are called maria (MAR-ee-a), from the Latin word for "seas".
q The singular form is mare (MAR-ay).
q Example: Mare Tranquilitatis
is the "
The Moon has a synchronous rotation.
q This means that we only see one side of the Moon from the Earth.
q Does the moon rotate?
o Yes
q Is the farside always dark?
o No
q Is the a part of the moon that we never see?
o Yes...but...
Theories of the Moon’s Formation
q Fission
q Capture
q Binary Accretion
q Collision-ejection theory - proposes that the Earth was struck by a Mars-size object within the first 100 million years after our planet formed.
Tides
q What causes tides on Earth?
q What are Spring Tides?
q What are Neap Tides?
q Mercury has phases like our Moon.
q Mercury is only seen near the Sun in the morning or evening.
q Surface Features: Impact Craters, Scarps (or cliffs), No Atmosphere
q Surface Temperatures: 800°F during the daytime, -280°F at night
q Mercury was first imaged by the Mariner 10 spacecraft.
q Slow Rotation: Mercury makes only 3 rotations every 2 orbits. This is an example of spin-orbit resonance.
q Venus has phases like our Moon.
q Venus is always seen near the Sun as a "morning star" or "evening star". (Seen more often than Mercury.)
q Surface Features: Lava Domes, Shield Volcanoes, A Few Craters
q The surface is completely hidden beneath a permanent cloud cover.
q The surface of Venus was first imaged with radar by the Magellan spacecraft.
q The Greenhouse Effect heats Venus' surface: 900°F
q Retrograde Rotation: Venus is the only planet that rotates "backwards". (243 days for one rotation)
q Mars has polar ice caps made of carbon dioxide.
q The surface of Mars has a red color due to large quantities of iron in its soil.
q The Viking landers sent back close of views of a barren Martian surface.
q The largest volcano in the solar system, Olympus Mons, can be found on Mars.
q Early Earth-based observations showed canali on the surface of Mars. Canali means “water channel”.
q There is clear evidence that Mars once had great quantities of water. But it is now “locked up” in...
o Subsurface permafrost
o polar caps
q Mars may once have had a dense atmosphere. But it was lost to...
o Space
o Subsurface permafrost
o polar caps
q Moons of Mars
o Two tiny moons, Phobos and Deimos, orbit close to Mars' surface.
o These are probably asteroids captured by Mars early in its history.
q Mars has neither civilization nor fields of plants, but microbial life forms still seem possible.
q Over 86% of its mass is hydrogen, and 13% helium. The remainder consist of methane, ammonia, and water vapor.
q Jupiter rotates rapidly - about once every 10 hours.
q Jupiter has reddish belts and light-colored zones.
q Jupiter has cyclones caused by differential rotation. e.g. The Great Red Spot
q Jupiter has a thin ice ring.
q Galilean Satellites of Jupiter
o Io has lots of sulfur volcanoes caused by tidal forces from Jupiter.
o Europa has a fractured ice surface and perhaps has an oxygen atmosphere.
o Ganymede is the largest satellite in the solar system and has a thick mantle of ice.
o Callisto is a dark icy world with numerous impact craters.
q Jupiter host at least 16 moons.
q Several space probes have imaged Jupiter and its moons.
o Voyager 1
o Voyager 2
o Galileo spacecraft
q Saturn's surface and interior are similar to that of Jupiter.
q Saturn rotates rapidly with differential rotation.
q Saturn’s Rings...
o ... are less than 1 mile thick.
o …are composed of fragments of ice and ice-coated rock.
o …are made up of thousands of ringlets.
o … are kept in shape by shepherd satellites.
o … were formed by perhaps a comet passing within the Roche Limit of Saturn.
q The large dark gap in Saturn's rings is called Cassini's division.
q Saturn host at least 22 moons. Only 7 are spherical.
q Titan is the largest of Saturn's moons and has a rather thick atmosphere.
q Voyager 1 and Voyager 2 flybys gave us data and pictures of Saturn and its moons.
q The Cassini spacecraft is now on its way to Saturn.
q First planet in recorded history to be discovered.
q Discovered by William Herschel in 1781.
q The planet's axis of rotation lies almost in the plane of its orbit.
q The surface of this planet is almost featureless and has a blue-green color caused by methane clouds.
q Uranus has 15 moons of which only 5 can be seen from Earth-based telescopes.
q The rings of Uranus were first discovered using stellar occultation.
q Uranus was visited by Voyager 1 and 2 in the 1980's.
q ...was predicted to exist due to perturbations in the orbit of Uranus.
q ...was discovered in 1846.
q ...also has a blue-green color caused by methane clouds on the surface.
q ...has a Great Dark Spot similar to Jupiter's Great Red Spot.
q …has faint ice rings.
q
q Triton
is
q
q Pluto was discovered in 1930 by Clyde Tombaugh.
q The Pluto-Charon system is more like a pair of ice planets.
q Both Pluto and Charon have synchronous rotation.
q Belt Asteroids - are those found between the orbits of Mars and Jupiter.
q Trojan Asteroids - share Jupiter's orbit about the Sun.
q There are empty regions in the asteroid belt called Kirkwood Gaps.
(Created by Jupiter’s gravity)
q The asteroids are probably fragments of planetesimals, the bodies from which planets were built.
q About 20 to 30 new asteroids are discovered every year.
q There are over 30,000 known asteroids.
q Examples:
Ceres (diameter = 625 miles)
Gaspra (3 by 12 miles)
Toutatis (0.5 by 2 miles)
q There are two reservoirs for comets
q Kuiper Belt
q Oort Cloud
q The Sun produces two tails on comets: the dust tail and the ion tail.
q Examples: Halley's Comet, Hale-Bopp, Shoemaker-Levy 9
Comet Halley
q It orbits the Sun every 76 years.
q It was imaged in 1986 at close range by Giotto, a European satellite.
Comet Shoemaker-Levy 9
q Was shatter by Jupiter’s gravity in 1992.
q All pieces hit Jupiter in the summer of 1994 leaving dark impact scars.
Meteors
q meteoroid - small debris moving though space
q meteorite - space debris found on Earth
o Types
§ iron meteorites
§ chondritic meteorites
q meteor
o a.k.a. “shooting star”
o a small bit of rock that is heated by friction in the Earth’s atmosphere and gives off light
q meteor shower - results from the Earth passing though a comet's path