The Solar System
Chapter 8
Section 8-1
Planet Motion
Gravitational forces formed the solar system and
cause the planets to orbit the Sun
Objectives:
• Compare and contrast geocentric and
heliocentric models
• Describe each planets position
• Classify the planets based on location and
characteristics
Models of the Solar System
• Early scientists believed that the Earth
was the center of the Universe because
of their limited knowledge
• Hierarchy: Sun/Star, Planets, Solar
system, Galaxies, Universe
Geocentric Model
• The Earth was considered the center of
everything
• The Greek Scholar Ptolemy believed
that the Earth was surrounded by a
series of spheres that contained planets
and stars
• Planet comes from the Latin word
“planasthai” meaning “to wander”
Geocentric Model
Heliocentric Model
• 1543 the Polish astronomer, Nicholas
Copernicus proposed a new model
“Sun-Centered”
• He stated that the moon revolves
around the Earth and the Earth around
the Sun
Heliocentric Model
• In 1625, using a primitive telescope, the
Italian astronomer, Galileo Galilei reinforced
the ideas of Copernicus
• Observed the phases of the planet Venus and
the moons of Jupiter
• Confirmed that the Sun was the center of the
solar system
Galileo Galilei
Understanding the Solar
System
• In the 1626, the astronomer Johannes Kepler
concluded that the planets move around the
Sun in an elliptical orbit instead of
spherical/circular
Understanding the Solar System
• Kepler also discovered that the planets move
at different speeds around the Sun, the closer
the planet is to the Sun the faster it
moves/revolves
• One revolution/year on Mercury is 88 days
and it takes Neptune 164 years to complete
one revolution
Classifying Planets
The Planets can be classified in three ways
depending upon the information that you are
looking to obtain:
1. Size
2. Characteristics
3. Location
Classifying Planets
• Characteristics (Terrestrial and Jovian)
• Location (Inner Planets and Outer
Planets separated by the asteroid belt)
• Size (Jupiter to Mercury)
Origin of the Solar System
• The latest evidence suggests that our solar
system formed with a group of stars 4.6
billion years ago
• The force of gravity pulled and condensed a
collection of dust and gas “cosmic garbage”
together that was probably the result of an
exploded star
Origin of the Solar System
• As this collection of gas and dust began
to condense and spin it took shape.
• Temperatures inside the cloud increased
allowing the hydrogen in the cloud to
fuse into our Sun…and the rest is
history!
Origin of the Solar System
• Why do we think this? With the
improvements in satellite technology
we can actually see it happening
elsewhere in the galaxy/universe
Other Solar Systems
• Remember that our Sun is just one of
trillions of stars in our galaxy…it is a
very common type of star.
• Each star is a sun…not all have planets
revolving around them…but we have
discovered 200 so far that do.
Andromeda
Galaxy
Section 8-2
The Inner Planets (Inferior)
Objectives:
• Compare and contrast the other inner
planets with Earth
• Describe the important characteristics
for each inner planet
• Evaluate the success of various missions
to Mars
Planets Near the Sun
The planets near the sun are made of solid
material/rock “terrestrial” because the pull of
the Suns gravity attracted the heavier elements
close to it as the solar system formed
Size Comparisons
Mercury
• The smallest and closest planet to the
Sun
• Mariner 10 passed by from 1974-1975
and photographed 45% of the surface
• The core is suspected to be iron based
upon the magnetic field surrounding the
planet
Mercury
Mercury’s Surface
• Mercury’s core condensed and shark
faster that the outer layers resulting in a
surface the is covered with high cliffs
and mountains
Mercury’s Atmosphere?
• Mariner 10 did pick up traces of gas
surrounding the planet, but due to the
low gravitational pull of the planet the
gases are thought the be remnants of
solar wind
• Temperature varies from 427 C (800 F)
to -170 C (-274 F)
Venus
• Same size as Earth
• Venus has a dense atmosphere that is mostly
carbon dioxide
• The atmosphere contains sulfuric acid
• 2% of the suns light actually hits the planets
surface due to thick clouds
• Temp is a constant 450 to 475 C (1000 F)
Venus
Satellites to Venus
• 1970’s Russia/Soviet Union sent the
Venera probes that photographed and
mapped the surface
• In 1995 the United States probe
Magellan also mapped the surface in
more detail
Earth
• Third planet from the Sun with a
temperature range that allows water to
be in all three states (solid, liquid, and
gas)
• Meteors tend to burn up in the
atmosphere
• Ozone layer protects life from harmful
solar radiation
Earth
Mars
• Fourth planet from the Sun
• “Red Planet” due to iron oxide “rust” in the
surface rock
• Tilted 25 on its axis causing seasons
• Frozen carbon dioxide and (water?) at the
north and south poles
• Dust storms as seasons change make the
planet appear to change color
Mars
Mars Atmosphere
• The Martian atmosphere is much thinner
that that of the Earth and does not filter out
the harmful rays of the Sun
• Temperature ranges from 37 C (95 F) to -123
C (-300 F)
Martian Moons
• Mars has two heavily cratered moons,
Phobos and Deimos.
• Phobos is slowly falling toward Mars
and will eventually impact (50 million
years from now) the surface of Mars
Was Mars Once Covered with Water?
• This is still in dispute, the current
temperatures do not allow for liquid or
gaseous water to exist on the surface
• There are indications in the land that look
like the result of running water, but are more
likely the result of the seasonal dust/wind
storms
NASA on Mars
• NASA began sending meaningful missions to
Mars in 1971 (Mariner 9)
• The satellites photographed a large valley in
the surface that may have been carved out by
water. (it would stretch from California to
New York) Valles Marineris
Vallis
Marineris
Satellites and Mars Missions
•
•
•
•
•
•
Mariner 9
Viking
Mars Global Surveyor
Mars Pathfinder
Odyssey
Mars Exploration Rover Mission (Spirit and
Opportunity)
Viking Probes (1976)
The two probes, Viking I and Viking II
photographed the surface and landed taking
rock samples and looking for signs of life
Global Surveyor, Pathfinder, and
Odyssey
• These three missions photographed the
walls of the Valles Marineris and found
it to be layered. Does that indicate
sedimentary rock (water) or is it
volcanic in nature?
Mars Exploration Rover Mission
(2003)
These “rovers” found deposits of hematite that
are usually the result of crystallization in
standing water.
Martian Meteorites
• Meteorites have also been found on Earth
that are believed to have come from the
surface of Mars as the result of impact.
• A meteorite from Mars (ALH84001) was
found in 1996 in Antarctica and appeared to
show fossilized microorganisms.
Section 8-3
The Outer Planets
Objectives:
• Compare and contrast the outer planets
• Describe the important characteristics for
each outer planet
• Evaluate the success of NASA missions
Galileo and Cassini
Size
Comparisons
Why are the Outer Planets so
Different?
• Compared to the inner planets, the outer
planets contain large amounts of hydrogen,
helium, methane and ammonia
• The outer planets had more material to work
with because of their distance from the Sun
and its gravitational pull
Jupiter
• The fifth planet from the Sun
• The largest planet, contains double all of the
other planets combined
• 90% hydrogen, 9 % helium, 1% ammonia,
methane and water vapor
• If the planet has a core, we do not know its
composition or size
Jupiter
Jupiter
• The atmosphere contains clouds of
white, red, tan and brown swirling in
high pressure gas
• The Giant Red Spot is a continuous
storm that has been raging for at least
300 years
Space Probes to Jupiter
• 1979 Voyager I and Voyager II
• 1995 Galileo
• Made observations about the
atmosphere and the moons of Jupiter
Jupiter’s Moons
• More than 60 moons orbit the planet
• Most of them are captured asteroids, but
four of them are large enough to be
considered planets
• Ganymede, Callisto, Io, Europa
Saturn
• The sixth planet from the Sun
• Nine times larger than Earth
• Largest and most complicated ring
system of any planet
• 60 known moons revolve around it
• Similar composition to that of Jupiter
with an unknown core
Saturn
Saturn’s Rings
• Saturn's rings are made up of billions of ice
and rock particles
• The particles are the result of asteroid
collisions and the pull of Saturn's gravity and
each of its moons
• There are actually made up of thousands of
individual ringlets
Uranus
•
•
•
•
•
•
The seventh planet from the Sun
Four times the size of Earth
Voyager II flew by it in 1986
At least 27 moons
Smaller ring system than Saturn
The clouds around the planet give it bluegreen color
Neptune
• The Eighth planet from the Sun
• Voyager II passed by in 1988
• Internal planetary heat causes high
winds
• At least 13 moons, Triton is the largest
• Faint ring system
• Methane gas gives it a true blue color
Neptune
Dwarf Planets
• Pluto, discovered in 1930, orbits once every
248 years
• Eris, discovered in 2005, orbits once every
557 years
• Ceres, discovered in 1801, orbits once every
4.6 years. Located in the asteroid belt
between Mars and Jupiter
Comets and Other Objects
• Comet (rock, dust, ammonia, and water) that
begins to melt and form a coma (head) and
tail as it approaches the Sun.
• Asteroid (rock similar to that of the terrestrial
planets)
• Meteorite (smaller asteroid)
Section 8-4
Life in the Solar System
Objectives:
• Evaluate other planets in the solar system
and the possibility of them containing life
• Examine life forms that exist in exotic
locations on Earth
• Discuss locations in which life might exist on
other planets
Life As We Know It
• We often think that we are the only form of
life in the Universe, but that is life as we
understand it.
• Life on this planet is carbon based and needs
liquid water
Exotic Life on Earth
• Life has been found on Earth in places that
we never thought to look or never could look
before technology
• Extreme heat, extreme cold, extreme
pressure
• This opens up the possibility of life existing in
places we never thought possible
Can Life Exist on Other
Worlds?
As we investigated the other seven planets we
have seen no real evidence that life as we know
it could exist anywhere else in our solar system
as we know it.
Life on Mars?
During most of the Earth’s history, life was
mostly made up of one-celled organisms, could
those organisms have also existed on Mars if
there was indeed liquid water there at one
time?
Face on Mars…
Europa (Moon of Jupiter)
• The Galileo space probe showed us that
Europa has ice covered oceans
• On Earth we have found life in extremely cold
water, could it exist on Europa as well?
Titan (Moon of Saturn)
• Titan appears to have an atmosphere of
nitrogen, water, and hydrocarbons
• Could these be the recipe for life as we know
it on Titan?