Inner Planets

Mercury

Venus

Earth

Mars

Asteroids

Distance from the Sun (million Km)

60

110

150

230

-

Time to Travel once round the Sun ( Earth years)

0.2

0.6

1

2

-

Diameter (Km)

5000

12000

12800

7000

-

Outer Planets

Jupiter

Saturn

Uranus

Neptune

Distance from the Sun (million Km)

780

1400

2900

4500

Time to Travel once round the Sun ( Earth years)

12

30

84

160

Diameter (Km)

140000

120000

52000

50000

Dwarf Planets

Eris

Ceres

Pluto

Distance from the Sun (million Km)

6000

Time to Travel once round the Sun ( Earth years)

250

Diameter (Km)

3000

Mercury:  this is the smallest planet, roughly the size of our moon and is closest to the Sun.  Its mass is not great enough to produce a strong gravitational field and for this reason it is unable to sustain atmosphere. The gases just simply drift into space.  The side of Mercury facing the Sun can reach temperature high enough to melt lead (430ºC), while the dark side drops to -170ºC.

Venus:  It is almost the same size as the Earth.  It is an unpleasant planet.  It has a rocky surface, covered by dense clouds of sulphuric acid and carbon dioxide.  These clouds of gas entirely hide the surface of Venus. This traps the Sun's heat due to the ' Super Greenhouse Effect' and for this reason it surface temperature is higher then that of Mercury (approximately 500ºC).  Without this atmosphere, Venus' temperature would be a lot lower.  It reflects a lot of light, so Venus looks bright.  It is also known as the 'Morning and the evening Star'. 

Earth:  If you view the Earth from space, it looks blue with swirls of clouds.  Its surface is rocky, with mountains and canyons, which are covered with water and ice.  It is the only planet with water, oxygen and living thing.  Planet Earth has just the right conditions for life to exist, because it is at the right distance from the Sun.  It has one moon.  No doubt, other stars in the universe might have planets with the same life sustaining conditions.

Mars:  It is called the red planet.  It is dry cold desert of red rock, with massive mountains and canyons.  It is most like Earth.  It has a thin atmosphere of carbon dioxide (95%), nitrogen, oxygen, water vapour and noble gases.  there is no life on it.  It has 2 small moons.  The dark patch is a giant volcano.

Jupiter: The largest of the planets and the coldest.  It has no solid surface, it is a liquid giant.  It is made up of mainly liquid hydrogen and helium,  surrounded by these gases and clouds.  The bands of colour , in Jupiter are produced by different regions in the atmosphere.  The great red spot is thought to be an area where the atmosphere constantly swirls around a giant storm.  This spot is 3 times the size of Earth. Jupiter is surrounded by 16 moons.

Saturn:  A gas giant, very much like Jupiter.  It is made mostly of hydrogen and helium. It has the most striking ring system of all the outer planets.  The 18 rings are made from billions of tiny particles of rock and ice.  They are held together in orbit by the pull of Saturn's gravity.  It has 18 moons.

Uranus: Another gas giant, made up of hydrogen and helium.  It is different from other planet, because it is lying on its side as it goes round the Sun.  The spin axis of Uranus is tilted at 98°, so that at times it poles point towards the Sun, giving rise to extreme seasons.  It has 15 moons and 11 rings.

Neptune: Appears in the sky as tiny blue-green speck, using even the most powerful telescope on Earth, because it is so far away from the Sun, where the light is one thousandth as strong as on Earth. Neptune is a ball of water and rock, consisting of atmosphere of hydrogen, helium and methane.  The great dark spot is a storm, about the size of Earth.

Pluto: The smallest and the outer most of all the planets, discovered in 1930.  It is of low density, composed of rock and ice, with frozen methane on its surface and thinly spread in the atmosphere.  Pluto's elliptical orbit occasionally takes it within the orbit of Neptune.  It has one moon.