Inner-planets

Inner planets 

 Mercury,Venus,Earth,and Mars are the solar system's inner planets. On the face of it ,they are world apart but underneath the
surface ,it is a different story. The inner planets all formed from the same material abut 4.6 billion yers ago. All are a mix of rock and metal, with intriors that are roughly divided into layers.
The heavier metals are concentrated towards the centre, while the lighter rock is on top.Each of these planets was bombarded by asteroids and comets early in the solar system's history,and each has been affected by volcanic activity too. Mercury's heavily cratered face still bears the scars of the early bombardment, but the surfaces of other three worlds have changed over time.

In the Sun’sglare 

 Mercury is the smallestof the Solar System’s planets and lies closest to the sun. It is a lifeless world that has hardly changed in 3 billion years. The planet’s entire surface is pitted with crashed in to it while Mercury was young. The craters range from small,bowl-shaped ones to the huge Caloris Basin ,which is nearly one-third the width of the planet. Mercury orbits the Sun more quickly than any other planet,but it nrotates slowly:for evry tow orbits, it spins around just three times. So a “day”on Mercury (sunrise to sunrise)takes 176 Earth days.Such long days and nights, coupled with a evry thin atmosphere,giv Mercury the greatest surface temperature range of all the planets. In the daytime, the surface is hot enough to melt lead, but at night it’s cold enough to liquefy air

 Lava land 

 Venus is sometimes described as Earth’s twin because it’s almost the same size as our planet and has a similar internal structure.But the tow worlds are vary different. Any astronaut who tried to walk on venus would be killed in seconds. The surface is as hot as the inside of a pizza oven, and the crushing air pressure is 90 times greater then that on Earth.

 Living world 

 Third out from the Sun ,Earth is the largest of the inner planets.It’sthe only planet with liquid water flowing freely on the surface, and it’s the only planet in the Universe known to sustain life.

 The red planet 

 The second smallest planet in the Solar System,Mars is half the size of Earth. It’s sometimes called the red planet because of its rusty colouring. A vast canyon called valles Marineris stretches a qurter of the way around this frozen desert world.