Dead planet!

Living things need air and water to stay alive, and neither of these is available on the Moon. The atmosphere of the Moon is a higher vacuum than can be created in most scientific laboratories....

How far away is the Moon?

The distance of the Moon away from the Earth was settled once and for all after the Apollo astronauts left a small reflector on the Moon's surface. Lasers were directed at this...

What is a lunar month?

For thousands of years people have used the Moon to measure the passing of time and the seasons. The Moon revolves around its own axis every 29 1/2 days, which is also the time it takes...

Why does the Moon shine?

The Moon is by far the brightest object in the night sky, but it has no light of its own. Moonlight is simply the reflected light of the Sun. Parts of the Moon that are not in sunlight...

What is a lunar eclipse?

The Earth casts a long shadow into space, and when this shadow passes over the Moon it causes an eclipse. A lunar eclipse can only happen during a full Moon, when the Sun is directly...

What is the Moon?

The Moon is the Earth's only satellite, and it has been orbiting our planet for at least 4,000 million years. It is a rocky sphere about 3,476 km in diameter, which is about one-quarter...

What are meteorites made of?

Meteorites are made of rock or metal. They enter the Earth's atmosphere at speeds of at least 11 km per second, which makes them glow brightly. Several thousand meteorites enter the...

What happens when a meteorite hits the ground?

When a large meteorite hits the ground it can produce a crater. Meteorite craters are rare on the Earth, because the atmosphere slows the meteorite and also usually burns it up. Many...

Space bombardment

Many asteroids have struck the Earth already, and many scientists believe that such an impact resulted in the extinction of the dinosaurs about 65 million years ago. At that time an...

What is an asteroid?

Asteroids are small rocky or icy bodies that orbit the Sun. They are sometimes called minor planets. Most asteroids are found in an orbit between Mars and Jupiter, and more than 7,000...

What is the tail of a comet?

You cannot see the nucleus of a comet with the naked eye, but you can sometimes see its tail. It appears as a smear of light that moves very gradually across the sky. As a comet...

What is a comet?

Comets are often described as 'dirty snowballs’. The solid centre, or nucleus, of a comet consists mostly office mixed with sooty material. The nucleus is quite small, and is usually...

What are shooting stars?

Shooting stars, or meteors, are streaks of light that cross the night sky, although they can only be seen for one or two seconds. They are caused when a solid piece of rock called a...

Do other planets have moons?

Apart from the Earth, most of the other planets have moons although these are usually quite small. Saturn has the most moons - it has at least 18. Some of these are very strange. Enceladus...

What makes Neptune blue?

Neptune is covered with a blue ocean of liquid methane gas. It is a very cold place at the farthest part of its orbit it is 4,000 million km from the Sun. Its surface temperature...

Which are the outer planets?

Uranus, Neptune and Pluto are the outer planets. They are so far away that they were discovered only when powerful telescopes were developed. Pluto, the smallest and most remote of...

What are the rings of Saturn?

Shining rings of billions of tiny chips of ice, rock and dust surround Saturn. The rings reflect light strongly and can be clearly seen through a telescope from the Earth. It was first...

Where is the largest known canyon?

On Mars! There is no running water to wear away the rocky landscape on Mars, so huge valleys can survive for millions of years. A system of enormous canyons called the Valleys Mariners...

The Red Planet

Mars is covered by a stony desert that contains lots of iron oxide, making it appear a rusty-red color. At one time Mars had an atmosphere containing oxygen, and it has valleys through...

Could we live on Venus?

Science fiction writers thought that life might exist beneath the thick clouds covering Venus. We now know that conditions there are too extreme for life as we know it. Robot spacecraft...

What are sunspots?

Groups of black blotches appear on the surface of the Sun every 11 years. These blotches are called sunspots. They are areas that are about 1,000°C cooler than the rest of the Sun's...

Crash bang!

In 1994, the most spectacular event ever seen by human eye in the Solar System happened when a newly discovered comet struck the planet Jupiter. The comet had been shattered by Jupiter's...

What are the inner planets?

The four planets that are nearest the Sun are called the inner planets. In order from the Sun, they are Mercury, Venus, Earth and Mars. The inner planets are different from the outer...

Which planet is closest to the Sun?

Mercury is the closest planet to the Sun. The temperature on the side of the planet facing the Sun is as high as 430°C.The shaded side of Mercury which faces away from the Sun is...