Inner Planets

The Inner Planets

The Inner Planets are the four planets  which have the closest orbits to the Sun.  These are Mercury, Venus, Earth and Mars. It is this close proximity to the Sun that allowed the the temperatures for the rock and metal to condense . They all are solid with rocky surfaces which is different to the Outer Plants which are Gas Giants.


Mercury is one of the densest planet in the solar system and it is the closest planet to the Sun. In appearance its is similar to our Moon -  it is a similar size, a grayish colour and covered with impact craters. Mercury is the closest planet to the Sun. It can be seen with the naked eye, although it is difficult to recognize because it so close to the Sun. It looks like a star in shortly before Sun rise and shortly after Sun set.   Its atmosphere is very thin and it gives virtually no protective shield from the solar radiation. So the temperature varies from 400C during the day and -200C at  night.


Venus is the second planet from the Sun. Has thick cloud cover and it is the hottest planet in the solar system and this is due the 96.5% carbon dioxide in its atmosphere causing a green house effect and trapping the heat. A part from the Moon it is the bightest object in the sky – it is often called the Morning Star.  It can easily seen with the naked eye – in the morning  and evening.


Earth is the third planet from the Sun and can be easily seen without a telescope. Its atmosphire protects its surface from radiation and provides ideal conditions of life. It is the only planet  in the Solar System that is covered with liquid water.


Mars is the forth planet from the Sun and it is the last inner planet. It can be seen with the naked eye and a large but a telescope can start to bring out surface detail. It has a thin atmosphere.  It has a red appearance which is due the surface rust of iron minerals - due to this it is known as the Red Planet. It has two moons – Phobes and Deimos.







Distance from Sun

36 million miles

67 million miles

93 million miles

142 million miles


3,031 miles

7,500 miles

7,926 miles

4,218 miles

One Rotation

59 Earth days

243 Earth days

24 hours

24.4 Earth days


88 Earth days

225 Earth days

365.256 Earth days

687 Earth days






Matt Armitage & H.C.O