SCARIEST asteroids threaten Earth: NASA explains what the dangerous PHAs are

The majority of asteroids occupy a specific place in the inner solar system. They reside within the asteroid belt between Mars and Jupiter. Yet, there are a few that stray from their orbits and come near the Earth. To identify all asteroids that fly close to our planet, NASA uses the classification of Near-Earth objects or NEOs. These are the asteroids that come within a range of 50 million kilometers to the Earth. However, within this category exists a terrifying sub-population of asteroids that can destroy the Earth if they ever struck our planet. NASA calls them ‘potentially hazardous asteroids’. But what are they exactly?

What are potentially hazardous asteroids (PHA)?

As per NASA, any NEO asteroids that are larger than 140 meters in diameter (460 feet) and have a probability of coming closer than 7.48 million kilometers (4.65 million miles) to the Earth, then these particular asteroids are called potentially hazardous asteroids. The classification indicates that these are the highest-risk asteroids that can cause harm to us. These space rocks come close enough to have a high chance of being pulled in by Earth’s gravity and are large enough to not disintegrate in the atmosphere. In short, these are the asteroids that can make it to the ground and cause a massive impact crater, destroying everything that is there- from life to homes.

The threat of potentially hazardous asteroids

According to the NASA CNEOS website, as many as 31000 NEOs have been discovered by the space agency. Among them, 2,300 have been identified as potentially hazardous asteroids. NASA postulates that many of these asteroids were once part of the main asteroid belt but as the solar system evolved, they shifted their orbit slightly, moving out of the belt.

Interestingly, about half the NEOs are bigger than 140 meters, but because of the large distance between them and the Earth, they have not been considered a threat.

NASA and other space agencies across the globe have also been working on improving their preparedness against such asteroid attacks. For example, NASA recently conducted its DART (Double Asteroid Redirection Test) mission where it launched a spacecraft to hit an asteroid and change its orbit. Other similar asteroid defense methods which have been kept in the discussion are the usage of nuclear weapons to explode asteroids, using rocket boosters to change their direction and remote detonators for a similar effect.

However, none of these methods have truly been tried and tested and if a massive asteroid were to head for our planet, it is hard to tell how successful the methods are likely to be.