The discovery of asteroid 2024 YR4 has nations scrambling.
The asteroid, discovered in December 2024, initially had an estimated 1 percent chance of hitting Earth. Recent data raised the possibility to 2.3 percent, raising alarms internationally.
Discovered by the Asteroid Terrestrial-impact Last Alert System (ATLAS) in Chile, the asteroid’s size is an estimated 40 to 90 meters (130 to 300 feet) in diameter. Its estimated impact date is December 22, 2032, with the odds currently at 1 in 45.
Though its potential impact is more than 7 years away, there’s a severe time crunch. The asteroid will become increasingly difficult to observe after April 2028 due to its orbit, limiting data collection. It’s a Level 3 threat on the Torino Scale, meaning it has a greater than 1 percent chance of causing significant localized damage.
If YR4 collides with Earth, it could cause damage similar to the 1908 Tunguska event that flattened more than 2,000 square kilometers of forest. Though the exact impact location is unknown, scientists have identified a risk corridor that spans Northern South America, the Arabian Peninsula, and South Asia.
The threat has prompted global action already. The urgency could expedite advancements in asteroid detection, tracking, deflection, and even space mining, while encouraging international collaboration and policy shifts.
NASA plans to employ the James Webb Space Telescope for precise assessments of the asteroid’s size and trajectory, while the European Space Agency is collaborating with global agencies to strategize.
For the first time in history, the world can realistically counter the existential threat an asteroid strike poses. Even if the chances of impact drop to zero, the asteroid’s discovery is a reminder about how vulnerable the planet is to universe-scale forces.
China’s Planetary Defense Push
The Chinese government is accelerating the advancement of its planetary defense capabilities in light of the newly discovered asteroid. The potential threat prompted China’s State Administration of Science, Technology, and Industry for National Defence to initiate a recruitment drive for the effort.
They’re aiming to deploy a spacecraft to collide with a near-Earth asteroid while an accompanying observer monitors its impact in real-time. The national space administration plans to launch its first planetary space test mission by 2030, targeting a near-Earth asteroid to test the capability of a kinetic impactor.
Kinetic Impactor
A kinetic impactor is a spacecraft designed to crash into an asteroid at high speeds to change its trajectory. NASA demonstrated its feasibility as part of its DART project in 2022.
DART, short for Double Asteroid Redirection Test, sent a kinetic impactor 11 million km (7 million miles) away from Earth to hit the Dimorphos asteroid. Its rate of speed exceeded 22,000 km/h or 20x the speed of sound.
Though the concept proved successful once, a kinetic impactor would face big challenges targeting asteroid YR4. Dimorphos, about the size of the Pyramid of Giza, is a loose rubble pile asteroid, which makes its orbit easier to alter with force.
Though scientists believe 2024 YR4 is about half the size of Dimorphos, they aren’t sure if it’s a solid chunk or loose pile of smaller rocks held together by gravity. If smaller, YR4 could be easier to deflect, but if it’s solid a bigger impactor or multiple hits may be required. Dimorphos is also more stable and roundish compared to YR4.
The asteroid that may hit Earth rotates every 19.5 minutes, suggesting an elongated or irregular shape. A fast-spinning asteroid could distribute energy unpredictably, making precise deflection harder.
As part of a well-known binary system, Dimorphos’s orbital mechanics were more well understood. Without precise orbital data, targeting the YR4 asteroid would be riskier, with a miniscule miscalculation resulting in a miss or ineffective deflection.
NASA also had years of runtime with DART. In a worst case scenario, the deflection method could just make the asteroid hit a different part of the planet.
Nuclear Options
A more extreme option is nuclear deflection.
NASA and the Lawrence Livermore National Laboratory have run tests showing that standoff detonation could push an asteroid enough to avoid an impact with Earth. After detonation, the nuclear device would heat the asteroid’s surface, creating a push that alters its path.
The Los Alamos National Laboratory simulated using multiple small nuclear blasts to nudge an asteroid rather than destroying it. Scientists believe a 1 megaton explosion could deflect an asteroid several hundred meters if done years in advance.
For the YR4 asteroid, however, nuclear weapons might be over kill. though they could prove useful if there’s no time left for other deflection methods.
The spotlight on planetary threats could open up funding for theoretical deflection methods like gravity tractors.
NASA researchers Edward Lu and Stanley Love introduced the concept in 2005, suggesting a spacecraft could hover near an asteroid to exert a gravitational pull. The ESA has explored making the technology feasible, and the B612 Foundation, a nonprofit dedicated to planetary defense, has promoted the concept as a viable deflection strategy.
Transitioning from theoretical research to practical development requires significant investment. The YR4 asteroid is likely too small to effectively be set off course by a gravity tractor before impact.
However, the technology could potentially shield the planet from much larger asteroids that could wipe out civilization.
Laser Ablation
Another proposed method for deflecting asteroids involves attacking them with high-powered lasers.
The laser ablation process creates a jet-like plume that generates enough thrust to alter the asteroid’s trajectory. The University of California Santa Barbara has baked out a conceptual design for what it calls the DE-STAR, short for Directed Energy System for Targeting Asteroids and Exploration. A smaller, spacecraft mounted version called DE-STARLITE would perform laser ablation over an extended period.
The Planetary Societies Laser Bees Project has explored the feasibility of deploying multiple laser-equipped spacecraft. The organization says experiments have validated the concept, demonstrating its potential effectiveness.
The discovery of YR4 could also boost the emerging space mining industry. Increased funding for near-Earth object detection could lead to improved tracking technologies to classify asteroids based on mineral composition, making mining missions more viable.