Earth’s top asteroid defences

Context:

If an asteroid threat emerged, Earth would need to be ready. Scientists are continually working to give the planet the best range of defensive strategies.

Asteroid defence

Four strategies are most likely, but many others are being explored to give us the best chance of deflecting a fast-travelling visitor from space.

Hide in the basement :For asteroids less than 20 metres in diameter, people could evacuate the affected area and then hunker down and take cover.The impact of a larger asteroid would be a catastrophe to a region, a continent or the entire world depending on its size.
Send in the nukes:Instead of burying the device near the centre of the threatening object, nuclear deflection scenarios involve stand-off bursts: The blast energy vaporises part of the asteroid and propels the space rock onto a new and safer path, far enough away from Earth that radiation and fallout wouldn’t be a problem.
Ram it with a spaceship: The kinetic impactor (KI) technique could provide a third option — and it can be (and is being) tested. The KI technique is very simple: ram a spacecraft into the asteroid of concern and use the spacecraft’s momentum to change the momentum (and orbit) of the asteroid.
Let gravity do the work:The technique would involve operating a spacecraft of very large mass very near the asteroid of concern, and using the mass of the spacecraft to attract the asteroid. Because the spacecraft position could be controlled it could tug the asteroid in any direction and change its orbit so it misses the Earth.

Asteroids

Asteroids are also known as minor planets.
They are rocky remnants left over from the early formation of our solar system about 4.6 billion years ago.
Most asteroids are irregularly shaped, though a few are nearly spherical and are known to have a small companion moon (some have two moons).

Classification of Asteroids:

Main Asteroid Belt: The majority of known asteroids orbit within the asteroid belt between Mars and Jupiter.
Trojans: These asteroids share an orbit with a larger planet, but do not collide with it because they gather around two special places in the orbit (called the L4 and L5 Lagrangian points). There, the gravitational pull from the sun and the planet are balanced.