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Although it will not collide with Earth, the asteroid once labelled “urban killer” has now returned to the spotlight as it may hit the moon this time.
KTLA spoke with Davide Farnocchia, navigation engineer at NASA’s Jet Propulsion Laboratory. He shared how scientists tracked the changing paths of the 200-foot asteroid.
“You could call it a city killer, but none of the cities are at risk. The Earth is out of the way,” Farnockia said. “But the moon isn’t.”
First discovered in December 2024, the asteroid 2024 YR4, is closely monitored in 2032 as a potential lunar shock factor.
2024 YR4: “Urban Murderer” threatened to collide with Earth in 2032
A few weeks after its discovery, YR4 made headlines when the probability of hitting the Earth surged to 3.1%, becoming the most threatening asteroid observed for over 20 years. That risk earned it to 3 on the Turin scale. This indicates that rarely used classifications signal uncertain but reliable threats.
Farnocchia recalled the moment when his team had to warn astronomers of shock probability.
“We had to inform them and say, ‘Look, this object should get a higher priority in the schedule to watch the asteroid tonight,” recalls Farnocchia. “We needed more data to prove it was off the planet, and that’s what happens almost always.”
However, instead of fading out of concern, the risk level for YR4 has increased.
By mid-February 2025, asteroids had a 32nd chance of affecting Earth. The effect of that size could have destroyed the metropolitan area if it hit the land.
“YR4 represents the most important impact risk of the past 20 years,” Farnocchia said. “But we told us early that the probability would likely decrease as we get more data, and that’s exactly what happened.”
By the end of February 2025, improved measurements had helped to eliminate the impact on the planet, but the story did not end there.
It’s not a threat to the Earth, but what about the moon?
While the Earth was off the risk list, the moon quietly replaced it.
In May 2025, scientists were far from sight since their last look at the YR4 on NASA’s James Webb Space Telescope. The data, released in June, refined the predicted route on December 22, 2032, increasing the chances of a monthly impact to 4.3%.
This is up from 3.8% in April to just 1.7% at the beginning of the year.
Still, Farnocchia emphasized: “The moon is smaller than Earth, but it’s a larger body, so even a 200-foot asteroid is not going to do much.” He pointed out that it would not change the movement of the moon.
Also, while it may sound prominently 4.3% of the time, it is still considered low by risk standards. Still, it’s rare for Farnocchia to see the moon become a potential target.
“That should be less,” he said. “In fact, you have a greater impact on the Earth than the Moon – it checks out. It’s much easier to hit the Earth than the Moon… But now the Moon happens to be in the realm of possibilities.”
The 2024 YR4 may not be surprising, but Apophis will
If the 2024 YR4 hits the moon, don’t expect a light show.
“If it hits the moon, the impact is not visible to the naked eye,” Farnockia said. “You’ll need a pretty big telescope, but still, it may be difficult to detect from Earth.”
But Skywatchers don’t have to wait long for something even more dramatic.
On April 13, 2029, the asteroid Apophis (approximately 1,100 feet wide) is closer to Earth than many satellites, and wears a rare and safe sight.
“It’s getting so close, and given its size it’s brighter to the naked eye. It’s going to be as bright as a tiny dipper star,” Farnockia said.
Apophis ‘Flyby’ is one of the closest recorded to an object of that size to date. NASA says it may be the first such event that humans have witnessed on modern instruments.
“Asteroids approach Earth on average every millennia, so events like this may not have happened at any time in recorded human history,” the organization says. “Undoubtedly, this is the first time that happened when humans had the skills to observe it.”
This composite image shows the moon (left) and asteroid 2024 YR4 (right) captured on the Gemini Southeres scope in Chile. (International Gemini Observatory/Noirlab/NSF/Aura/M. Zamanivia AP) Davide Farnocchia, navigation engineer at NASA’s Jet Propulsion Laboratory, can be seen in an interview with KTLA. July 2025 (KTLA) This image is made available by the University of Hawaii Asteroid Impact Alert System and shows an arrow with the asteroid 2024 YR4 on December 27, 2024. (European Space Agency via AP) This animation shows the distance between the Apophis asteroid and Earth at the time of the closest approach of the asteroid. The blue dots are many satellites orbiting our planets, while the pink represents the International Space Station. (NASA) This image, made available by the University of Hawaii’s Asteroid Impact Alert System, shows the movement of the asteroid 2024 YR4 for approximately an hour on December 27, 2024 (via ATLAS/HAWAII UNIVERSITY OF AP) This image, provided by NASA, shows the view from orbit. (Ernie T. Wright/NASA via AP)
How good is NASA to predict impact?
It’s very good – and it gets better.
“We found some very small objects before we reached Earth. They burn harmlessly, but we predict that the effects and location felt like a huge achievement,” Farnockia said.
New observation and modeling techniques allow us to predict not only the location of impact, but also the recovery of fragments from impact.
“Recently, we were able to predict where the impact was, and recover the metstone. This is kind of interesting because it is the final verification that predicted the correct impact point,” he said. “One colleague was informed of the expected impact in Canada, so he just went outside and set up a camera to watch it. It was really cool.”
Why is it important?
The moon is not in real danger, but the 2024 YR4 has become an important case study of NASA’s planetary defense system. It was the first object Apophis climbed to 3 on the Turin scale, and the first object to be tracked with a James Webbspace Telescope, improving impact projection by nearly 20%.
“There’s a lot to say about the YR4. It was really interesting to see the trajectory behaved as expected,” Farnockia said. “I like to see how predictions evolve with each new set of observations, which is a sign that the model is working well.”
NASA expects YR4 to look at another round of observations in 2028.
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