To be clear: The asteroid is not going to hit us.
There was a while there when it seemed like it could. Suffice to say those were heady days in the asteroid-tracking community. But as of March 2021, NASA has confirmed that there is absolutely zero chance the space rock known as 99942 Apophis will strike this planet for at least 100 years. So, phew. Cross that particular doomsday scenario off the list.
What remains true, however, is that on Friday, April 13, 2029, an asteroid wider than three football fields will pass closer to Earth than anything its size has come in recorded history.
An asteroid strike is a disaster; an asteroid flyby, an opportunity. And Apophis offers one of the best chances science has ever had to learn how the Earth came to be — and how we might one day prevent its destruction.
In the movies, incoming asteroids appear without warning from the depths of space and speed directly toward us until missiles or Bruce Willis heroically destroy them.
In real life, asteroids orbit the sun on elliptical paths. They are often spotted years, if not decades, before a potential collision — which is not great for dramatic tension but better for planetary survival.
Apophis was discovered in 2004. After calculating its potential orbits, astronomers were startled to realize it had a 3% chance of hitting Earth in 2029. In a nod to its horrifying potential, they named it Apophis, an Egyptian god of chaos.
“We were shocked,” said Paul Chodas, who manages NASA’s Near-Earth Object Program Office at the Jet Propulsion Laboratory in La Cañada-Flintridge. “That is very serious and, actually, a very unexpected and rare event.”
Astronomers use a color-coded warning system called the Torino Scale to gauge the degree of danger an asteroid or comet presents to Earth in the next 100 years. Since the scale’s creation in 1995, none of the roughly 30,000 near-Earth objects known to exist in the solar system had ranked higher than 1 on the zero-to-10 scale.
Apophis was a 4.
The longer astronomers track an asteroid, the more clearly defined its orbit becomes. Within a few months, scientists were able to rule out the possibility of a 2029 strike. Within a few years, they were able to dismiss the even smaller chance of a hit in 2036.
And in 2021, radar observations confirmed that Apophis will not strike when it passes us in 2068, leaving Earth in the clear for at least a century.
With humanity’s safety assured — from this threat, at least — the coast was clear to geek out on some asteroid science.
“We’ve never seen something that large get that close,” said Lance Benner, a principal scientist at JPL.
“Close,” in the space world, is a relative term. At its nearest, Apophis will pass roughly 19,000 miles (31,000 kilometers) above Earth’s surface. That’s about one-10th the distance to the moon.
