CHAP. 3.3 & 3.4 – THE INNER AND OUTER PLANETS
- The four inner planets are Mercury, Venus, Earth, and Mars. They are inner planets because they have
solid surfaces and called terrestrial plants (earth or land planets).
- The five outer planets are Jupiter, Saturn, Uranus, Neptune, and Pluto. They are outer planets because
all of them have surfaces are just gases (“gas giants”) – except for Pluto which has a solid surface.
- The outer planets atmospheres are mainly hydrogen and helium.
- They also have a large gravitational pull which keeps gases on the planet’s surface.
- The smallest of the terrestrial planets (not much larger than the moon) and closest to the sun.
- The interior is thought to be dense iron.
- Based on upon evidence gathered from the Mariner 10 probe, Mercury’s surface is covered with flat
plains and craters.
- It has no atmosphere and weak gravity.
- It has the greatest temperature range than any other planet: 430 degrees Celsius during the day and -170
degrees Celsius at night.
- Venus revolves around the sun in 7.5 Earth months but it takes 8 Earth months for it to revolve around
- Unlike most the planets and the moons, it rotates from east to west.
- Venus’ atmosphere is so thick with sulfuric acid and carbon dioxide. It acts like a blanket. In other
words, the pressure of Venus’ atmosphere is 90 times greater than Earth’s.
- It also traps heat so Venus is the hottest planet in the solar system with an average surface temperature
of 460 degrees Celsius. This trapping of heat by gases is called the greenhouse effect.
- The Magellan probe showed that Venus’ surface is mainly rock and active volcanoes.
- The Earth has three main layers – a crust, a mantle, and a core.
o The crust is solid and rocky. It covers the mantle.
o The mantle is a layer of hot, molten rock. It covers the core.
o The core is mainly iron and nickel. It is important to note here that the outer core is liquid but
the inner core is solid.
- The Earth is unique in that 70% of it is water at the surface. This has contributed to Earth’s surface
changing over time.
- It has a change of 4 seasons.
- Mars’ surface is iron rich. As a result, it gives Mars a reddish-color.
- Mars atmosphere is 95% carbon dioxide.
- The surface temperature on Mars ranges from -140 degrees Celsius to 20 degrees Celsius.
- There is a theory that large amounts of water may have flowed on Mars’ surface in the long distance
past due to evidence of canyons and coastlines.
- There now, scientists have found frozen water on the polar caps on Mars and water vapor (gas) in Mars’
- Mars is known for its dust storms that can last up to two years.
- The largest volcano in the solar system is on Mars and it is called Olympus Mons.
- Mars has to moons - Phobos (fear) and Deimos (terror)
- Jupiter is the largest of all the planets. It is 2 ½ times bigger than all the planets combined.
- Jupiter is known for its famous Great Red Spot. The Great Red Spot is a storm that is never-ending and
blows winds hundreds of kilometers per hour in strength.
- It is theorized that Jupiter’s has a dense core of rock and iron. The core is surrounded by a liquid mantle
of hydrogen and helium.
- The pressure from Jupiter’s atmosphere is 30 millions greater than Earth’s.
- Jupiter has many moons but it is known for its main four: Europa, Callisto, Lo, and Ganymede.
- Saturn is the second largest planet in the solar system and is known for the rings that surround the
planet. The rings are made of dust, rock, and ice.
- Saturn’s largest moon is Titan (it is larger than Mercury).
- Uranus is 4x bigger than Earth and has a blue-green color to it. The blue-green color is due to the
presence of methane in the atmosphere.
- It rotates on its axis once every 17hours. However, Uranus is titled at an angle of 90 degrees from
vertical. It looks like it is turning on its side.
- It also has rings like Saturn and about 25 moons which range from icy surfaces to lava-flowing surfaces.
- Neptune is a cold, blue planet and its atmosphere contains visible clouds.
- It is theorized that Neptune is shrinking, which is causes its core to heat up and release heat.
- It has 13 moons and the largest moon is Triton.
- Pluto is the smallest and densest among the planets.
- It has one moon called Charon.
- It takes Pluto 248 Earth years to orbit the sun just once.