'God of chaos' asteroid can hit Earth, but only if THIS happens. 'The odds of...'

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Apophis, the "god of chaos" asteroid, has a higher chance of hitting Earth than previously thought, new analyses suggest. The asteroid is moving towards our planet and will make a dangerously close approach in 2029. 

Apophis was first discovered in 2004 and it was placed at level 4 on the Torino impact hazard scale - 0 means no chance of hitting and 10 means "a collision is certain" and might cause global climatic catastrophe.

Since NASA started monitoring potentially hazardous Near-Earth Objects (NEOs), this was the first asteroid to be assigned a rating of four on the scale. NASA describes the rating as, "A close encounter, meriting attention by astronomers."

As per current observations, the asteroid will safely pass by Earth, posing no threat in 2029, 2036 and 2068. However, the new study takes into account a slight chance that something hits Apophis while it is en route to our planet. 

Canadian astronomer Paul Wiegert looked at the odds of a small object colliding with Apophis and setting it on a course towards Earth. Wiegert and co-author Ben Hyatt had earlier ruled out a collision but still found a small chance of a collision with other material.

The astronomers tried to study what size object could change the trajectory of Apophis and put it on a route on which it might hit Earth. They also studied other scenarios of an object hitting it which can put the asteroid on an Earth-bound trajectory in the future after 2029. 

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What they found was that an impactor of around 0.6 metres (2 feet) can push the asteroid into one of the 2029 "keyhole" trajectories. This would set it up for a later collision with our planet. However, an impact in 2029 will happen only if Apophis collides with an object of around 3.4 metres (11.2 feet).

How likely is a collision?

The likelihood of an asteroid hitting Apophis is extremely low. Even if an impact does happen, the direction would also matter. Wiegert studied the number of objects over 3.4 metres in size in space and says the odds of an asteroid impacting it between now and 2029 are exceptionally low. 

"The odds of an unseen small asteroid deflecting Apophis enough to direct it into a collision with Earth in 2029 (d ≳ 3.4 m, Δv > 5 × 10−2 m s−1) are approximately 10−8," Wiegert says in the study.

"Given that only 5% of such impulses are in the correct direction to generate an Earth impact, the overall probability of a small impact directing Apophis into a collision with the Earth is less than one in 2 billion."

However, for a later impact after 2029, he puts the odds at less than one in a million. Despite being good odds, the risk of an impact still exists. 

How do we know if Apophis has moved?

To know if this has happened, Wiegert says we need to wait another three years. "An additional element of the story is that Apophis has been largely unmonitored by telescopes since May 2021 and will remain so through 2027," he explained. 

This is because "of the relative geometry of Apophis, Earth, and the Sun, which puts the asteroid in the daytime sky for the time span in question."