1. Our Solar System
Ag Earth Science
Mr. Silva

2. The Terrestrial Planets
 The four planets closest to the sun.
 Mercury, Venus, Earth, and Mars
 The terrestrial planets are much like
Earth.
 The four inner planets:
 Are relatively small and dense
 Have rocky surfaces (crusts), mantels, and
iron cores

3. More on the First Four
 Mercury and Mars have crusts that are
scarred by craters.
 Earth and Venus do not have craters because
their surface is continually eroded.
 Common characteristics of the terrestrial
planets:
 Higher temperature than outer planets
 Have few (if any) moons
 No rings around the terrestrial planets

4. Mercury
 Characteristics:
 Smallest and closest to the sun
 Dense with large Iron core
 Fastest moving planet - 88 day revolution
 Temperature and Atmosphere:
 It takes 88 days for sunrise to sunset
 During the day, temperature = 430 deg. C
 At night, temperature = 170 deg. C
 Virtually NO atmosphere - temp makes particles
move fast, little gravity makes it easy for
particle to escape into space

5. Venus
 Characteristics:
 The brightest object in Earth’s night sky (with the
exception of the moon)
 Rotates in the opposite direction to which it revolves
around the sun
 Rotation rate is VERY slow - takes 243 days to rotate on
its axis (a day is longer than a year!)
 Temperature and Atmosphere:
 Difficult to study because of clouds
 Atmosphere is so thick that pressure is 90x greater than
that on Earth
 Atmosphere is made mainly of CO2 which traps heat and
increases surface temp
 Surface temp is 470 deg. C

6. Earth
 Earth = Suitable atmosphere and
temperature for water to exist as liquid!
 H2O supports tens of thousands of different
species of living organisms and has shaped
the surface through erosion.
 Has gravity to hold most gas molecules =
thick atmosphere
 Geologically alive!

7. Mars
 Characteristics:
 Most Earth-like of all planets
 Weathering of iron-rich rock give it red tint
 Has largest volcano in solar system (Olympus Mos)
 Atmosphere and Temperature:
 Thin atmosphere and distance = temp range of -140
deg. C to 20 deg. C
 Atmosphere is mainly CO2 (much like Venus but
much thinner)
 No liquid water on Mars - but thought that there
once was
 Mars also has seasons due to the tilt of its axis

8. Asteroids
 Beyond Mars is a region known as the
asteroid belt
 Astronomers have discovered more than
10,000 asteroids and more are thought to
exist
 Asteroid are:
 >1 kilometer in diameter
 Only 3 are larger than 500 kilometers across
 It used to be thought that asteroids were
fragments of a shattered planet - not what is
thought today

9. Scientific Discovery
• It is said that Scientific Discovery can happen in
different ways:
• Discovery by accident
• Theories predict phenomena that scientists try to find
• Uranus (Yoor uh nus) and Neptune were discovered by
these two methods
• Uranus discovered by chance - thought it was a dim
star
• Neptune was found when someone predicted that
there was something affecting Uranus’ orbit.

10. Gas Giants
• The “Gas Giants” are the next four planets in the
Solar System
• Jupiter, Saturn, Uranus, and Neptune
• Common Characteristics:
• Much colder than terrestrial planets
• More massive than terrestrial planets
• Composed of mainly Hydrogen and Helium
• No solid surface - intense pressure means that H and He
exist in liquid form
• Small dense cores of metal and rock

11. Jupiter
• The first planet beyond the asteroid belt and the
largest/massive planet in the solar system
• Jupiter could hold more than 1,300 Earths and is named for
the ruler of the Roman Gods
• Jupiter is composed of mainly H and He
• Atmosphere:
• Clouds on Jupiter move fast because Jupiter moves fast
• Brown bands are colder and move faster than the white bands
• The great red spot is a giant storm on Jupiter, caught between bands
of warm and cold air
• These storms don’t dissipate like they do on Earth - the Great Red
Spot was first observed in 1664

12. Jupiter’s Moons/Fun Facts
• Jupiter has over 50 moons!
• Ganymede and Callisto are the size of Mercury
• Io and Europa are the size of Earth’s moon
• Ganymede, Io, and Europa have metal cores and rocky
mantels (Io is covered in active volcanoes - Ganymede, Europa,
and Callisto are covered in ice)
• Scientists believe that the ice on Europa rests on top of a liquid
salt water ocean
• FUN FACTS:
• One day on Jupiter is less than 10 hours on Earth
• It takes almost 12 Earth years for Jupiter to revolve around the sun
• The Great Red Spot is the size of three Earths

13. Saturn
• The second largest planet in the solar system and known for its
rings!
• Rings are ice particles or ice covered rock - most are snowball sized
• Rings are 274,000 kilometers in diameter yet only tens of meters thick
• Atmosphere:
• Largest atmosphere of any in the solar system
• Saturn has the lowest average density of any planet
• Atmosphere is made of H and He
• Scientists think that He condenses and as He raindrops fall towards the
center of the planet, their energy is changed to heat

14. Uranus
• Uranus is another Gas Giant which is extremely cold and has
an atmosphere made of H and He
• Like other Gas Giants, it is assumed that Uranus has a rocky
core surrounded by a thick mantel layer of liquid water and
dissolved ammonia
• Uranus has rings, although they are not as impressive or
reflective as Saturn’s rings
• Uranus is tiled on its side, and it rotates in the complete
opposite direction that it revolves around the sun
• The northern and southern hemispheres alternate between
being exposed to the sun for years - causing disturbances on the
surface

15. Uranus’ Moons/Fun Facts
• Uranus has more than 20 moons
• FUN FACTS:
• Uranus is thought to have been tilted on its side by a
collision with another planet sized object
• The rings and moons of Uranus follow the irregular
rotation of the planet
• One day on Uranus is about 17 Earth hours
• It takes almost 84 Earth years for Uranus to revolve
around the sun
• Blue-Green color comes from methane in the atmosphere

16. Neptune
• Neptune has approximately the same size and
composition of Uranus
• Neptune has clearly visible cloud patterns in its
atmosphere, and gets the blue tint from methane in
the atmosphere
• Neptune has large storms in its atmospere which last
for many years
• The Great Dark Spot was identified by Voyager 2 in 1989
and then disappeared in 1994

17. Neptune’s Moons/Fun Facts
• Neptune has 8 moons
• Triton is the largest moon - has a thin
atmosphere and an icy crust
• FUN FACTS:
• Neptune also has a small band of coal colored
rings
• One day on Neptune is about 15 Earth hours
• It takes almost 165 Earth years for Neptune to
revolve around the sun.

18. Pluto – A Planet No More 
• Pluto is small and dense - much like the moons
of the Gas Giants
• Pluto is made up of a mixture of ice and rock
• Pluto has a single moon - Charon - which is
almost identical in size (almost like a double
planet)
• Pluto is now considered a “dwarf planet” and
is not recognized as having official planet
standing