THREATS TO THE EARTH

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COMETS

Asteroids are rocks in space, while comets are balls of dust and ice in space. There would be serious consequences if a large asteroid collided with the Earth.

Comets

Comets are balls of ice and dust that orbit the Sun. Their orbits are different to those of planets: they are highly elliptical (an oval).

A comet’s orbit takes it very close to the Sun, then far away, beyond the planets. The time to complete an orbit varies. Some comets take a few years, others millions of years.

The speed of a comet increases as it approaches the Sun. This is because the strength of gravity increase

Comets are often visible from Earth when they get close to the Sun. This is because the Sun’s heat vaporises material from their surface, forming a tail of debris

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ASTEROIDS

Asteroids are smaller than planets. They are rocks left over from the formation of the Solar System. Most are found in an ‘asteroid belt’ in orbit around the Sun between Mars and Jupiter. The minor planet Ceres is found here, too.

Asteroids can crash into each other. When they do, they can break apart and change orbit.

The orbits of some asteroids cross the Earth’s orbit. At various times during the Earth’s history, asteroids have hit it. A tremendous amount of energy was released, throwing up billions of tonnes of dust and hot rocks. Together with smoke from widespread fires, this blocked heat and light from the Sun. It changed the Earth’s climate, making it very cold.

It is thought that an asteroid colliding with the Earth helped to drive the dinosaurs to extinction. Scientists worry that an asteroid could hit again and cause a global catastrophe. The chances of this happening are very small, but the damage caused by a large asteroid would be huge.

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NEAR EARTH OBJECTS AND COLLISIONS

Asteroids are smaller than planets. They are rocks left over from the formation of the Solar System. Most are found in an ‘asteroid belt’ in orbit around the Sun between Mars and Jupiter. The minor planet Ceres is found here, too.

Asteroids can crash into each other. When they do, they can break apart and change orbit.

The orbits of some asteroids cross the Earth’s orbit. At various times during the Earth’s history, asteroids have hit it. A tremendous amount of energy was released, throwing up billions of tonnes of dust and hot rocks. Together with smoke from widespread fires, this blocked heat and light from the Sun. It changed the Earth’s climate, making it very cold.

It is thought that an asteroid colliding with the Earth helped to drive the dinosaurs to extinction. Scientists worry that an asteroid could hit again and cause a global catastrophe. The chances of this happening are very small, but the damage caused by a large asteroid would be huge.

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REDUCING THE THREAT OF NEAR EARTH OBJECTS

The asteroid belt

Most asteroids lie in the asteroid belt, between Mars and Jupiter.

Jupiter is a very large planet with a very large gravitational field strength. Its gravity stops rocks from coming together to form a planet. Instead, they orbit the Sun as asteroids.

Reducing the threat of NEOs

Scientists are searching for NEOs using telescopes. Over 4,000 have been detected, varying in size from a few metres across to over a kilometre across. NEOs could also be monitored using satellites.

If an NEO were to be detected on a collision course with Earth, it may be possible to deflect the NEO using explosions. If enough force could be applied early enough, the NEO could be nudged into a different trajectory that missed the Earth. NASA’s Deep Impact mission in 2005 showed that we can send a probe to an asteroid and hit it.

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Comments

Abdullahi

  • very good

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