Mercury and Venus:

Mercury and Venus are the two planets closest to the Sun. The conditions on each planet are very different.

Rocky Planets:

Both Mercury and Venus are made of solid rock, but they look completely different. About 60% of Mercury's surface is covered in craters caused by meteorites crashing into the planet. This makes it look very similar to Eorth's moon.

Venus has many volcanoes. There is a major difference between the atmospheres on the two planets. Mercury has almost no atmosphere. Venus has a thick atmosphere of corbon dioxide covered by spinning clouds of sulfuric acid.

Temperature:

Although Mercury is the closest planet to the Sun, Venus is actually the hotter planet. Mercury's temperature reaches 427 degrees Celsius during the day. Since there is no atmosphere to trap heat near the surface of the planet, the temperature falls to -180 degrees Celsius at night.

On Venus, any heat that finds its way through the thick atmosphere is trapped near the surface of the planet, producing a greenhouse effect. The temperature reaches 480 degrees Celsius. This heat also means water cannot exist as a liquid on either Mercury or Venus.

The inner solar system is separated from the outer by the asteroid belt.

The solar system is the port of the Milky Way galaxy which is a barred-spiral galaxy.

There were 9 planets in the Solar System until 2006 when the International Astronomical Union decided that Pluto could no longer be considered a plonet due to its size being smaller than our moon.

If all the planets were joined together, the Sun would still be more than 700 times bigger. It contains over 99% of the solar system's mass.

It takes two million years for gamma rays produced in the core of the Sun to reach its surface.

The Sun is the largest object the solar system. It is about 332 950 times more mossive than Earth.

The relationship between the Sun and the Earth drives the seasons, currents in the ocean, weather and climate.

The Sun has been burning for about five billion years and will bum for another five billion.

If you stood on Venus, the atmospheric pressure would be the same as if you were 900 meters underneath an ocean on Earth.

Much of the surface of Venus, including craters, has been covered in lava from previous eruptions.

Mercury and Venus are the only two planets in our solar system that don't have moons.

Mercury has the greatest variation in surface temperature of any planet in the solar system - can be over 600 degrees Celsius.

Because there is no wind or rain on the Moon, any footprints left by the astronauts should remain for millions of years.

It is thought that Earth was hit by a lorge object and the debris that was ejected into space joined together to form the Moon.

The official Latin name for planet Earth is Terra. It is named after the Roman goddess of fertility and growth - Terra Mater.

The Moon is the only other planet or satellite in the solar system that humans hove set foot upon.

The length of each Martian season is almost twice as long as a season on Earth.

Mars has the least hostile environment of all the other planets in the solar system.

Mars has two small moons. They have uneven shapes and may have originally been asteroids.

After the Sun, the Moon and Venus, Jupiter is usually the fourth brightest object in the sky.

Saturn is almost exactly the same as Jupiter, just smaller. The only striking difference is the rings around Saturn.

Saturn's rings are thought to be particles of an old moon which was smashed to pieces in a collision million of years ago.

Jupiter is made of hydrogen and helium gases which also make up the Sun. If Jupiter had been any bigger, it could have become a star.