Our Solar System is composed of 8 planets orbiting around one star: the Sun.
The 4 closest planets to the Sun are relatively small and telluric (made of rocks and metals).
While the the 4 others are enormous balls of gases.
Note: Pluto is not classified as a planet of our Solar System since 2006.
The importance of an atmosphere
Observe and compare Mercury and Venus. Then the Earth and the Moon.
Please read more on the atmosphere here
Mercury and Venus
Mercury is the closest planet to the Sun however Venus is much warmer. Why?
Because Venus’ atmosphere is dense and thick with too many greenhouse gases. These gases capture (and absorb) the Sun’s energy and Venus overheats.
The Earth and the Moon
The Earth’s average temperature is 15°
The Moon’s average temperature is -20°
Despite being at a similar distance from the Sun, their temperature is not similar.
The reason is that the glasshouse effect of the Earth’s atmosphere enable the Earth to retain the solar energy.
Without our perfectly balanced atmosphere, the Earth would be almost as cold as the moon.
Our source of energy
This star is a gigantic ball of fire burning hydrogen and producing heat and light.
It is our vital source of energy. Without it, life would be impossible on planet Earth.
Solar energy triggers:
- Water cycle,
- and photosynthesis.
- Diameter +/- 110 Earth
- Mass +/- 333 Earth
The smallest planet of our Solar System
It has a rocky surface with several craters and temperatures between day and night fluctuate a lot because it has no atmosphere to protect it.
- Diameter +/- 1/3 Earth
- Mass +/- 1/20 Earth
- Orbit 88 days
- Rotation 59 days
- Atmosphere none
The Evening Star
This planet has a very thick atmosphere. Greenhouse effect is so important that solar rays penetrate but can’t escape from it.
Venus is so hot that it continuously shines in our sky, it is a very useful guiding tool.
- Diameter +/- 1 Earth
- Mass +/- 1 Earth
- Orbit 255 days
- Rotation – 243 days
- Atmosphere very dense and acidic
The only (known) planet where life started.
It has an atmosphere containing appropriate greenhouse gases. Our atmosphere captures the right amount of solar energy while releasing the remaining heat.
- Diameter 13000 kilometers
- Mass 6 x 1024 kilograms
- Orbit 1 year = 365 days
- Rotation 1 day
- Atmosphere balanced
It has a rocky surface.
It has several craters because it has no atmosphere to protect it against meteorites and other celestial bodies.
Without atmosphere to temper it, there are important temperature fluctuation.
- Diameter +/- 1/4 Earth
- Mass +/- 1/100 Earth
- Orbit 28 days
- Rotation 27 days
- Atmosphere none
The red planet
The second smallest planet with the largest volcano of our Solar System.
It’s a rather cold planet : it is far away from the Sun and its very thin atmosphere does not retain the solar radiation (rays).
- Diameter +/- 1/2 Earth
- Mass +/- 1/10 Earth
- Orbit +/- 2 years
- Rotation +/- 1 day
- Atmosphere hardly none