Asteroids: Mass killers like no other- a primer (Pixabay)

Over billions of years, Earth has been bombarded by asteroids many time and these events have helped shape history and led it to become the human-dominated planet that we see today. (Pixabay)

However, it was not always so. Dinosaurs once dominated the Earth, but  an asteroid strike on Earth drove them into extinction and mammals, including humans, had the chance to overrun the Earth. So, mass-killers they may be, but to humanity, they did a favour. (Pixabay)

65-mn years ago, a nearly 9-mile-wide asteroid hit Earth. The resultant tragedy led to mass extinction of many species, including of dinosaurs. In fact, three-quarters of the planet's plant and animal species were destroyed. This was the Chicxulub asteroid.  (Pixabay)

So, what are asteroids? These are space rocks, small to big, that orbit the Sun like planets. (Pixabay)

Asteroids are the rocky remnants left over from the early formation of our solar system, which happened about 4.6 billion years ago. (Pixabay)

Asteroids are smaller than planets, often irregularly shaped, and in almost all cases, probably have no atmosphere. (Pixabay)

Sometimes, the gravity of nearby planets flings these asteroids out of their regular orbit to elsewhere in the Solar System. (Pixabay)

However, even before the dinosaur killer asteroid struck, there was another even larger asteroid that had hit Earth. Exactly what it destroyed and how it affected the future is still mystery. It was estimated to be twice the size of the asteroid Chicxulub. This was around 2 bn years ago.   (Pixbay)