The Solar SystemChapter 8

Section 8-1Planet 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 PlanetsThe Planets can be classified in three ways

depending upon the information that you are looking to obtain:

1. Size2. Characteristics3. 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 8-2The 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 SunThe 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 8-3The 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

http://solarsystem.nasa.gov/multimedia/gallery/Backlit_Saturn1.jpg

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 blue-

green 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 8-4Life 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?