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Planet Fact Sheet
The Inner or Terrestrial Planets
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Mercury, Venus, Earth and Mars share certain characteristics:
– All are rocky bodies.
– All have solid surfaces.
– Except for Mercury all have at least a thin atmosphere
They are called Terrestrial planets because of their resemblance to Earth.
Mercury
 Named after Speedy messenger of Roman gods
 Closest planet to the sun
 Revolution around the sun = 88 Earth days
 Rotation on its axis = 59 Earth days
 Crater-covered surface with steep cliffs
 Almost no atmosphere
Venus
 Named after Roman goddess of beauty and love
 2nd closest planet from the sun
 Revolution around the sun = 224 Earth days
 Rotation on its axis = 243 Earth days
 Venus and Earth are of almost the same size, mass, and density, but
differ greatly in other areas.
 Surface pressure = 91 times more than Earth’s
Earth
 3rd planet from the sun
 Revolution around the sun = 365 days
 Rotation on its axis = 24 hours
 Earth has one large moon.
 Geologic records indicate that over the last 250 million years, Earth’s
surface has undergone many changes.
Mars
 Named after Roman god of war
 4th planet from the sun.
 Mars is about 50% farther from the sun than Earth is.
 Its orbital period is 687 days
 It rotates on its axis every 24 hours and 37 minutes.
 Mars’s seasons are like Earth’s seasons because the same axis.
 Has the largest volcano in the solar system, Olympus Mons.
 About half the size of Earth. No geological activity likely now. No
magnetic field.
 Evidence of massive water erosion some time in the past. Scientists
are searching for liquid water now.
 Two satellites, Phobos and Deimos
 (possibly captured asteroids)
 High winds often create dust storms
The Outer or Jovian Planets
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Jupiter, Saturn, Uranus and Neptune share certain characteristics:
– All are large, gaseous bodies.
– All have very thick atmospheres, with possibly liquid interiors and
solid cores
– All have rings
They are called Jovian planets because of their resemblance to Jupiter.
Jupiter
 Named after the king of the Roman gods
 5th planet from the sun
 Jupiter is the largest planet in the solar system and has a mass more
than 300 times that of Earth.
 The orbital period of Jupiter is almost 12 years. Jupiter rotates on its
axis faster than any other planet—once every 9 hours and 50 minutes
 Jupiter has at least 60 moons.
 It also has several thin rings that are made up of millions of particles.
 Great Red Spot = hurricane-like storm (as much as 20,000 years old)
 Very high atmospheric pressure
 Giant magnetic field
Saturn
 Named after a Roman god
 6th planet from the sun
 Rotates every 10 hours and 30 minutes
 Revolves around the sun every 29.5 years
 Surrounded by rings made of icy particles; at least 7 major rings
 Violent atmospheric storms
 Very cold
 Has a large magnetic field
 Lowest density of all the planets
 The orbital period of Saturn is 29.5 years.
 Saturn rotates on its axis every 10 h and 30 min.
Uranus
 Named after the father of Saturn in Roman mythology
 7th planet from the sun
 Rotates every 17 hours
 Revolution around sun every 84 years
 Extreme atmospheric pressure; atmosphere is 11,000 kilometers thick
 Rotates on its axis at a 90 degree angle; appears laying on its side
 Rings of methane ice surround it
 Has at least 24 moons and at least 11 thin rings
Neptune
 Named for the Roman god of the sea
 8th planet from the sun
 Revolution around the sun every 164 years
 Rotation 16 hours
 Surface-ocean of water, liquid methane, and rocky core
 Five rings surround Neptune made of dust particles formed from
meteorites