‘City Killer’ Asteroid Now Has 3.1% Chance of Hitting Earth, Says NASA 

This image made available by University of Hawaii's asteroid impact alert system shows the motion of asteroid 2024 YR4 over about one hour, Dec. 27, 2024. (ATLAS / University of Hawaii / NASA via AP)
This image made available by University of Hawaii's asteroid impact alert system shows the motion of asteroid 2024 YR4 over about one hour, Dec. 27, 2024. (ATLAS / University of Hawaii / NASA via AP)
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‘City Killer’ Asteroid Now Has 3.1% Chance of Hitting Earth, Says NASA 

This image made available by University of Hawaii's asteroid impact alert system shows the motion of asteroid 2024 YR4 over about one hour, Dec. 27, 2024. (ATLAS / University of Hawaii / NASA via AP)
This image made available by University of Hawaii's asteroid impact alert system shows the motion of asteroid 2024 YR4 over about one hour, Dec. 27, 2024. (ATLAS / University of Hawaii / NASA via AP)

An asteroid that could level a city now has a 3.1-percent chance of striking Earth in 2032, according to NASA data released Tuesday -- making it the most threatening space rock ever recorded by modern forecasting.

Despite the rising odds, experts say there is no need for alarm. The global astronomical community is closely monitoring the situation and the James Webb Space Telescope is set to fix its gaze on the object, known as 2024 YR4, next month.

"I'm not panicking," Bruce Betts, chief scientist for the nonprofit Planetary Society told AFP.

"Naturally when you see the percentages go up, it doesn't make you feel warm and fuzzy and good," he added, but explained that as astronomers gather more data, the probability will likely edge up before rapidly dropping to zero.

2024 YR4 was first detected on December 27 last year by the El Sauce Observatory in Chile.

Astronomers estimate its size to be between 130 and 300 feet (40-90 meters) wide, based on its brightness. Analysis of its light signatures suggests it has a fairly typical composition, rather than being a rare metal-rich asteroid.

The International Asteroid Warning Network (IAWN), a worldwide planetary defense collaboration, issued a warning memo on January 29 after the impact probability had crossed one percent. Since then, the figure has fluctuated but continues to trend upward.

NASA's latest calculations estimate the impact probability at 3.1 percent, with a potential Earth impact date of December 22, 2032.

That translates to odds of one in 32 -- roughly the same as correctly guessing the outcome of five consecutive coin tosses.

The last time an asteroid of greater than 30 meters in size posed such a significant risk was Apophis in 2004, when it briefly had a 2.7 percent chance of striking Earth in 2029 -- a possibility later ruled out by additional observations.

Surpassing that threshold is "historic," said Richard Moissl, head of the European Space Agency's planetary defense office, which puts the risk slightly lower at 2.8 percent.

- Webb observations in March -

"It's a very, very rare event," he told AFP, but added: "This is not a crisis at this point in time. This is not the dinosaur killer. This is not the planet killer. This is at most dangerous for a city."

Data from the Webb telescope -- the most powerful space observatory -- will be key in better understanding its trajectory, said the Planetary Society's Betts.

"Webb is able to see things that are very, very dim," he said -- which is key because the asteroid's orbit is currently taking it out towards Jupiter, and its next close approach will not be until 2028.

If the risk rises over 10 percent, IAWN would issue a formal warning, leading to a "recommendation for all UN members who have territories in potentially threatened areas to start terrestrial preparedness," explained Moissl.

Unlike the six-mile-wide (10-kilometer-wide) asteroid that wiped out the dinosaurs 66 million years ago, 2024 YR4 is classified as a "city killer" -- not a global catastrophe, but still capable of causing significant destruction.

Its potential devastation comes less from its size and more from its velocity, which could be nearly 40,000 miles per hour if it hits.

If it enters Earth's atmosphere, the most likely scenario is an airburst, meaning it would explode midair with a force of approximately eight megatons of TNT -- more than 500 times the power of the Hiroshima bomb.

But an impact crater cannot be ruled out if the size is closer to the higher end of estimates, said Betts.

The potential impact corridor spans the eastern Pacific, northern South America, the Atlantic, Africa, the Arabian Peninsula, and South Asia -- though Moissl emphasized it is far too early for people to consider drastic decisions like relocation.

The good news: there's ample time to act.

NASA's 2022 DART mission proved that spacecraft can successfully alter an asteroid's path, and scientists have theorized other methods, such as using lasers to create thrust by vaporizing part of the surface, pulling it off course with a spacecraft's gravity, or even using nuclear explosions as a last resort.



River Seine Reopens to Public Swimming for 1st Time in a Century

A view of one of the three Seine swimming pools, Thursday, July 3, 2025 which will open during the 'Paris Plages' event from July 5 to Aug. 31 in Paris. (AP Photo/Aurelien Morissard)
A view of one of the three Seine swimming pools, Thursday, July 3, 2025 which will open during the 'Paris Plages' event from July 5 to Aug. 31 in Paris. (AP Photo/Aurelien Morissard)
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River Seine Reopens to Public Swimming for 1st Time in a Century

A view of one of the three Seine swimming pools, Thursday, July 3, 2025 which will open during the 'Paris Plages' event from July 5 to Aug. 31 in Paris. (AP Photo/Aurelien Morissard)
A view of one of the three Seine swimming pools, Thursday, July 3, 2025 which will open during the 'Paris Plages' event from July 5 to Aug. 31 in Paris. (AP Photo/Aurelien Morissard)

For the first time in over a century, Parisians and tourists will be able to take a refreshing dip in the River Seine. The long-polluted waterway is finally opening up as a summertime swim spot following a 1.4 billion euro ($1.5 billion) cleanup project that made it suitable for Olympic competitions last year.

Three new swimming sites on the Paris riverbank will open on Saturday — one close to Paris’ Notre Dame Cathedral, another near the Eiffel Tower and a third in eastern Paris.

Swimming in the Seine has been illegal since 1923, with a few exceptions, due to pollution and risks posed by river navigation. Taking a dip outside bathing areas is still banned for safety reasons.

The Seine was one of the stars of the Paris Olympics in 2024, whether as the scene of the ambitious opening ceremony or the triathlon and marathon swimming competitions. That didn't go without challenging hurdles such as rainfall increasing levels of bacteria, which postponed some competitions.

This city's authorities have given the green light for the public opening, with water quality results consistently in line with European regulations.

Making splashes in Paris city center “It’s a symbolic moment when we get our river back,” said sports coach and influencer Lucile Woodward, who will participate in the first amateur open water competition in the Seine on Sunday.

Woodward, who enjoyed a dip alongside Paris Mayor Anne Hidalgo just before the start of the Olympic Games, is confident things will go well.

“We're going to enjoy swimming in it, being there and setting an example," she said. "Once people will see that in the end there are hundreds of people who have fun and enjoy it, everyone will want to go!”

“For families, going to take a dip with the kids, making little splashes in Paris, it’s extraordinary,” Woodward added.

Olympic athletes competing in the river was a spectacular reward for the cost of the cleanup effort.

In the run-up to the Games, authorities opened new disinfection units and created a huge storage basin meant to prevent as much bacteria-laden wastewater as possible from spilling directly into the Seine when it rains.

Houseboats that previously emptied their sewage directly into the river were required to hook up to municipal sewer systems. Some homes upstream from Paris also saw their wastewater connected to treatment plants instead of the rainwater system flowing directly into the river.

Green flag for swimming Paris Deputy Mayor Pierre Rabadan said water is tested daily to confirm it's safe to swim. As on French beaches, different colored flags will inform visitors whether or not they can go in.

“Green means the water quality is good. Red means that it's not good or that there's too much current,” he said.

Tests have been in line with European regulations since the beginning of June, with only two exceptions due to rain and boat-related pollution, Rabadan said.

“I can’t make a bet on the numbers of days when we’ll have to close this summer, but water quality seems better than last year,” he added. “We’re in a natural environment ... so weather condition variations necessarily have an impact."

Last year, several athletes became ill after competing in the triathlon and open water races during the Olympics, though in most cases it was not clear if the river was to blame for their sickness.

World Aquatics stressed the conditions met the sport’s accepted thresholds.

“The legacy of these efforts is already evident, with the Seine now open for public swimming — a positive example of how sports can drive long-term community benefits,” the organization said in a statement to The Associated Press.

Skepticism remains about water quality Dan Angelescu, founder and CEO of Fluidion, a Paris and Los Angeles-based water monitoring tech company, has routinely and independently tested bacterial levels in the Seine for several years. Despite being in line with current regulations, the official water testing methodology has limitations and undercounts the bacteria, he said.

“What we see is that the water quality in the Seine is highly variable,” Angelescu said. “There are only a few days in a swimming season where I would say water quality is acceptable for swimming.”

“All we can say is that we can raise a hand and say look: the science today does not support the current assessment of water safety used in the rivers around Paris, and we think that there is major risk that is not being captured at all,” he said.

Some Parisians also have shown skepticism toward the idea of swimming in the Seine. The feeling is often reinforced by the water's murky color, floating litter and multiple tourist boats in some places.

Enys Mahdjoub, a real estate agent, said he would not be afraid of swimming, but rather "a bit disgusted. It’s more the worry of getting dirty than anything else at the moment.”

A dream come true Until the end of August, swimming sites will be open for free at scheduled times to anyone with a minimum age of 10 or 14 years, depending on the location. Lifeguards will keep a watchful eye on those first dips.

“It’s an opportunity, a dream come true," said Clea Montanari, a project manager in Paris. "It’d be a dream if the Seine becomes drinkable, that would be the ultimate goal, right? But already swimming in it is really good.”