Download Chapter 22 Touring our Solar System Solar System * Inventory • 1

Chapter 22
Touring our Solar System
Solar System
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Inventory
• 1 Sun
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• asteroids
• comets
• meteoroids
• The list will continue to grow
Planetary Properties
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Order of planets
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Sizes of Planets
* Sun contains 99.9% of solar system's mass
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Planets are relatively close to the Sun
* Planetary orbits become more widely spaced with increased distance from the Sun
• Distance roughly doubles with each planet (_____________________)
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Planets all revolve counterclockwise
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All planets have nearly the same orbital plane as the ecliptic except Pluto (170) and Mercury (70)
Terrestrial and Jovian Planets
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Terrestrial Planets (___________________________________________)
* Inner planets
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* Closely spaced orbits
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* Small sizes
* Predominantly rocky surfaces
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* High densities
* Slower rotation rates
* Weaker magnetic fields
* No rings
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* Thinner atmospheres, except Venus
• Due to low escape velocity - speed needed to escape a planet’s gravity
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Jovian Planets (Jupiter, Saturn, Uranus, Neptune)
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* Far from the Sun
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* Large masses
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* Low densities
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Faster rotation rates
Stronger magnetic fields
Many rings
Thick atmospheres
• Due to huge escape velocities
Formation of the Solar System
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* Cloud of gas and dust contracted
* Contraction created heat and pressure
* Sun formed at the hot center
* Giant, cooler swirling matter surrounded
* Cooler regions away from the Sun caused condensation and the formation of
proto-planets (proto-planetary disks = ___________________)
Earth and the Moon in Bulk
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Physical Properties
* Earth is more massive
* Earth is larger
* Earth is more dense
* Earth has stronger gravity
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• Escape velocity is more on Earth
* Rotation rate is faster on Earth
• Earth always sees the same side of the Moon’s face
• ________________________ – rotation period is equal to the revolution period
* Distance to the Moon is 384,000 km (240,000 miles)
* Overall Structure
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Effect of tides on Earth's rotation
* Earth's rotation is slowing down about 2 milliseconds every century
• Caused by the tidal effect of the Moon and Sun
* The Moon is spiraling away from Earth until the two become synchronized
• Eventually the Moon will be 550,000 km away
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Lunar Air
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* Very little amounts of water frozen in the rocks
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* Day temperatures can reach _________
* Night temperatures can reach __________
* No sound on the Moon
The Surface of the Moon
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* Dark areas meaning "seas“
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* Solid basaltic lava flows
* 3.2 - 3.9 billion years old
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Front side has more mare than back side
Largest feature – Mare Imbrium (sea of rains)
Distinctive Mare
• Oceanus Procellarum – “Ocean of Storms”
• Mare Nubium – “Sea of Clouds”
• Mare Serenitatis – “Sea of Serenity”
• Mare Tranquilitatis – “Sea of Tranquility”
• Mare Fecunditatis – “Sea of Fertility”
• Mare Crisium – “Sea of Crises”
• Mare Vaporum – “Sea of Vapors”
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Lunar Highlands
* Lighter colored uplands
• Rocks are more than 4 billion years old
• Heavily cratered
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Craters
* The moon is pocked with numerous craters
* Craters result from constant meteoritic impact
* Slideshow of craters
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Lunar Erosion
* No erosion is caused by weather
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• 10km crater occurs every 10 million years
• 1 m crater every month
• 1 cm crater every few minutes
• A steady "rain" of micrometeoroids eats the surface of the Moon
Origin of the Moon
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* A Mars sized object hit the Earth sending numerous pieces of debris into orbit around
the Earth
* Computer models suggest this possible scenario
* Debris would have coalesced into a solid object
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Mercury
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* Very small planet (close to the size of our Moon)
* Very dense, 2nd only to Earth
* Has numerous craters
* Difficult to see detail through a telescope because it’s so close to the Sun
* Looks a lot like our Moon
* Fast revolution (88 days)
* Slow rotation (59 days)
• 2 months long night
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* Night temperatures - __________)
* Daytime temperatures - (__________)
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• Life could not exist at those extremes
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No atmosphere because little gravity and hot temperatures would release air to space
Meteoroids and harmful radiation always bombard the surface
The poles are always very cold (-2350F) since the Sun’s angle is always very low
Mercury's surface
• Numerous craters
• No signs of water or weather
• Has some fault scarps
Internal structure
• Has a weak magnetic field (10X less than Earth)
• Large, heavy iron-rich core
• Unsure if core is liquid or solid
• Solid core prevents tectonic processes
Planet is dry and lifeless
4.6 billion years old
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2nd brightest object in night sky next to the Moon
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Covered in veil of clouds
225 day orbit
Very slow rotation (243 days)
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Similar to Earth in size, density, mass, and location (__________________)
Surface
• Can't see the surface because of clouds
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• Map of Venus vs. Earth
• Has mostly a smooth surface with rolling plains
• Erosion by the atmosphere is prominent
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– Most pronounced features are volcanic
– Large pancake lava domes exist
– Flattened due to high atmospheric pressures
– Resembles shield volcanoes on Earth
– No active volcano has yet been observed
– Rocks resemble basalt and granite
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– The 2 Landers lasted about an hour and eventually melted the circuitry
due to intense heat
– Very few visible craters
Internal Structure
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– Most likely due to the slow rotation
• Believed to be similar to Earth but with a softer crust due to the high
temperatures
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Atmosphere
• Average surface temperatures are near 9000F
• 96.5% carbon dioxide and 3.5% nitrogen
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• Constant lightning strikes with atmospheric pressures 90 times more than on
Earth
Venus has no moons
Life probably never existed on Venus
It’s sobering to realize how a planet so much like the Earth but just a little closer to the
Sun could have evolved so differently
Mars
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* Rotation period of 24.6 hours
* Atmosphere
• Thin layer of CO2
• 1/150th of Earth’s atmospheric pressure
• Mars has clouds and storms
• 95.3% carbon dioxide
• 2.7% nitrogen
• 1.6% argon
• Water vapor, oxygen, and carbon monoxide
* Surface
• Frozen polar ice caps of H2O and CO2
– Polar caps grow and shrink with changing seasons
• Numerous large volcanoes
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– Tharsis Ridge (Bulge)
– Currently unknown if volcanoes are active
• Huge canyons exist
– _______________ is a canyon much larger than the Grand Canyon
– Was not formed by running water
– Large crack formed as the Tharsis Ridge formed
– Flowing water is thought to create most canyons
• The northern hemisphere is more flat while the southern hemisphere is more
cratered
• Evidence of flowing water on Mars
– Runoff and outflow channels observed
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– Water seepage from hillsides
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– Springs from within a hill
– Ancient meandering stream channels
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– When the volcanism stopped the atmosphere was no longer provided
with water vapor and the land dried up
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• Mars has huge global wide dust storms
Several missions have landed on Mars
• Currently “Opportunity” and “Spirit” missions
Internal Structure
• No known magnetosphere
• Core must be non-metallic, non-liquid, or both
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• Temperatures can reach 700F near the equator during the day
* Mars has 2 moons (Phobos, Deimos)
• Very small and irregularly shaped
• Thought to be captured asteroids
* Mars photo slideshow
Jupiter
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* 21/2 times the mass of all the other planets, asteroids, and satellites combined
* If Jupiter was 10 times more massive, it would have been a star
* 3rd brightest object in night sky (telescope view)
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• Rotation = 9.9 hours, Revolution = 11.86 years
• Atmosphere experiences differential rotation
* Small tilt axis of 3 degrees
* Atmosphere
• Primarily H (86%) and He (14%)
• Parallel cloud bands exist
– Bands caused by convection from below
• ______________________ – a storm system 2 times the size of Earth
– A huge storm with smaller storms embedded
– Rotates like a huge hurricane
• Extensive colors in the atmosphere
• Extremely turbulent atmosphere
• Winds can reach 700 mph
• Probes reveal Jupiter’s atmosphere is layered
* Interior Structure
• Internal heat source produces huge convection
– Jupiter emits twice as much energy as it receives
• Huge magnetosphere (larger than the Sun)
• Outer core is liquid metallic hydrogen
• Very intense pressure in Jupiter
• Central temperature can reach 40,000 K
• Surface may be a gigantic ocean of liquid H
• Small central rocky core
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* Jupiter has a thin ring system
Saturn
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• Recent evidence reveals the rings may be slowly disappearing
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Saturn as viewed from Earth
• The changing views of Saturn’s rings
Fast rotation
• Rotation = 10.5 hours, Revolution = 29.6 years
Has great differential rotation
Tilt axis of 27 degrees
Atmosphere
• Similar atmosphere to Jupiter
– 92.4% H
– 7.4% He
• Atmospheric color not as vivid as Jupiter
• Clouds are thicker than on Jupiter
• Winds can exceed 930 mph
• Huge storms exist
• Very turbulent atmosphere
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Interior Structure
• Extensive magnetosphere produces aurora
• Much like Jupiter
• Thinner metallic hydrogen outer core
• Smaller rocky core
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Uranus (telescope view and VLT image)
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* Kepler's law could not predict the exact path, so this meant another planet must be
farther out past Uranus
* Much less massive than Jupiter and Saturn
* Nearly a twin to Neptune
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• Currently unknown why it's tipped over
* Uranus has rings as well
* Atmosphere
• Hydrogen 84%
• Helium 14%
• Methane 2%
• Blue color is due to the methane content
• Uranus is greenish compared to Neptune
* Rotation = 17 hours, Revolution = 84 years
* Has a central rocky core
* Has 27 moons
Neptune (Hubble view)
* 1st planet discovered using mathematical predictions
* Bluish fuzzy disk through a telescope
* Slightly smaller than Uranus
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* Rotation period = 17 hours
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Revolution period = 165 years
Atmosphere
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• High frozen cirrus clouds
• Winds can reach 1250 mph (windiest planet)
• Hydrogen 84%
• Helium 14%
• Methane 2%
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Neptune has rings
Neptune has 13 moons
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Discovered in 1930 by Clyde Tombaugh
• Partially named after famous astronomer, Percival Lowell, who searched for
the 9th planet until his death in 1916
Dirty frozen snowball
Recently demoted to dwarf planet status
• More resemblance to a large Kuiper Belt Object (KBO) than a planet
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• Recent findings reveal 2 more possible moons
Small Solar System Bodies
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Meteoroids
* Rocky fragment less than 100 m in diameter
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• Caused by friction heating up an object entering Earth's atmosphere
* Typically lasts for only a few seconds
* Meteorite * ____________________ - Earth passes into the remnants of an old comet’s tail
• Prominent events calendar
* Most are sand sized particles
* Primarily composed of iron and nickel
* Friction scars the meteoroid’s surface
* 4.4 - 4.6 billion years
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* Over 250,000 known asteroids
* Fragments of rocky material more than 100 meters in diameter
* Most are found in the Asteroid Belt
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* Revolve counterclockwise, except one
* Most stay close to the ecliptic plane
* More eccentric orbits than the planets
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• Share an orbit with Jupiter
• Remain 600 ahead and behind Jupiter in orbit
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• Also known as “Near Earth Objects” (NEO)
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• Most asteroids will remain within the belt
• Some have highly elliptical orbits
• Over 3000 known
• Current map of objects
• Become deflected by the gravities of Mars and Jupiter
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• most are less than 1km wide, but one is greater than 10 km
• Icarus (mile-wide) is an Earth-crossing asteroid
Largest asteroid “Ceres” is 587 miles wide
Asteroid views
• close-up view -- Irregular shaped -- Rotating
Landed on asteroid Eros in 2001
Asteroids originate from the fragments of broken planets and rocks that never formed
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Comets
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Discovered as a faint, fuzzy patch far from the Sun
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Mostly icy with some rocks and typically 1-10 km wide
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They brighten and develop a tail as it nears the Sun
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Have no internal light, only reflected
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Comet features
* Nucleus –
• Only the nucleus exists far from the Sun
* __________ - heated mass forms a gaseous and dusty glow around the nucleus
• coma gets larger as it nears Sun
• can be as large as Jupiter
* Tail
• Largest portion of a comet
• can stretch a distance of 1 AU
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– ion tail –
– dust tail - curved white tail of comet
• Tails are faced away from the Sun
* Hydrogen envelope - engulfs the coma and the tail
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Famous comets
* Hale-Bopp (1997)
* Hyakutake (1998)
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• 76 year period
• Documented every time since 240 B.C.
• In 1986, it was probed by ESA
• Will return in 2061
* Origins
• Short period comets originate in the _________________
– Periods less than 200 years
• Long period comets originate in the __________________
– Can stretch up to 100,000 AU
– Surrounds the entire solar system
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Comets have highly elliptical orbits
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They get smaller with each pass since they melt a little each time they pass by the Sun
Is Earth on a Collision Course???
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The solar system is cluttered with meteoroids, asteroids, comets, and comet remnants which
travel at great speeds
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We know that comets and asteroids have collided with Earth more frequently than 1st
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Evidence of impacts
* Earth is littered with over 100 impact structures called "____________“ and many are
very old
• Meteor Crater
– Winslow, AZ
– 25,000 years ago
– 1.2 km wide, 0.2 km deep
– Meteoroid was about 50 m wide
• Gosses Bluff (Australia) – 140 million years ago
• Manicouagan Crater (Canada) – 200,000 million
* Recent incidents
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– In 1908, a spectacular explosion occurred in Siberia from a "fire-ball"
brighter than the Sun
– Shock waves broke windows 1000 miles away
– Trees were scorched, de-limbed, and flattened up to 19 miles away
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– Object exploded just above the surface
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– Produced brilliant flashes and dark zones
• Asteroid 2002 MN
– 100 meter object passed within 75,000 miles of Earth (1/3rd the distance
to the Moon)
– It was detected 3 days after it passed our planet
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– In April 2029, this object will pass only 15,000 miles above Earth’s
surface (15 times closer than the Moon)
– Has a 350 meter diameter
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“Sooner or later” these objects will come back and make an impact
End of Chapter 22
Touring our Solar System
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