NASA’s Urgent 'Emergency' Move as Asteroid Threat to Earth Soars.
NASA has made an urgent decision as the chances of Earth being struck by a 'city-destroying' asteroid have risen to 1-in-43.
Though it may sound like something straight out of an apocalyptic sci-fi movie, the world’s space agencies have taken the rare step of addressing this increasing threat. Astronomers have warned that asteroid 2024 YR4 now has a 2.3% (1-in-43) chance of colliding with Earth in 2032, prompting international astronomers to use the James Webb Space Telescope (JWST) to analyze the asteroid’s potential impact.
The team of astronomers will focus on determining the exact size of 2024 YR4 and refining their calculations of its orbit. Initial estimates suggest the asteroid could measure up to 90 meters (300 feet) across, roughly the size of New York's Statue of Liberty or London’s Big Ben. The last time a major asteroid significantly impacted Earth was on June 30, 1908, in the Tunguska event. A roughly 50-meter-wide asteroid or comet exploded over the Siberian forest in Russia, flattening around 830 square miles (2,150 square kilometers) of trees. The explosion released energy equivalent to about 15 megatons of TNT, but luckily, it occurred in a sparsely populated area, and there were no confirmed human casualties.
The asteroid was first detected in December 2024 by the NASA-funded Asteroid Terrestrial-impact Last Alert System (ATLAS) station in Chile. Initially, it was thought to have only a 1.3% chance of striking Earth, but this slight risk made it the most significant potential threat to Earth, moving it to the top of NASA and ESA’s risk lists.
Despite early predictions, the exact size of 2024 YR4 remains uncertain. Scientists typically measure an asteroid's size by studying the light it reflects. Larger asteroids tend to appear brighter, but there are exceptions. As an ESA spokesperson explained, "2024 YR4 could be 40 meters [130 feet] across and very reflective, or 90 meters [295 feet] across and not very reflective."
2024 YR4 (pictured) was first detected in late December by NASA's Asteroid Terrestrial-impact Last Alert System in Chile. Scientists estimate a one-in-43 chance of impact in 2032.
Even the best telescopes on Earth face limitations due to Earth's atmosphere, which distorts light and makes it harder to capture accurate data. The JWST, however, is positioned 1 million miles (1.5 million kilometers) away from Earth, allowing it to avoid atmospheric interference and take clearer measurements. Equipped with infrared sensors, the JWST will also detect heat radiating from the asteroid, providing a more precise size estimate.
The data from JWST will help planetary defense experts assess the potential impact and decide if any action is necessary to deflect the asteroid. As the ESA spokesperson noted, "It is very important that we improve our size estimate for 2024 YR4: the hazard represented by a 40 m asteroid is very different from that of a 90 m asteroid."
If the asteroid proves to be around 90 meters wide, its impact could release the energy equivalent of 15 megatons of TNT—100 times the power of the Hiroshima bomb, which caused between 100,000 and 180,000 casualties. Such an impact would flatten structures and cause fatalities up to 2 miles (3.2 kilometers) from the impact site. However, these effects would be localized and wouldn't cause global devastation. By comparison, a much larger asteroid like Bennu (500 meters wide) could trigger an "impact winter" by releasing enough dust to cool the Earth by several degrees.
The European Space Agency has been granted emergency access to the James Webb Space Telescope (pictured) to more precisely measure the asteroid's size.
The JWST is set to make two observations of 2024 YR4. The first will occur in March, when the asteroid reaches its peak brightness, and the second in May, when it travels farther into space. These observations will help refine predictions of the asteroid's orbit and determine its temperature changes due to solar exposure. Scientists expect that the risk of impact will decrease as more data is gathered.
The JWST's observations will be limited to just four hours of the telescope's highly competitive schedule. These hours were taken from the "director's discretionary time," a budget reserved for urgent operations. Any data collected about 2024 YR4 will be made publicly available for transparency.
What Can Be Done to Prevent an Asteroid Collision?
Currently, NASA lacks the capability to deflect an asteroid heading directly for Earth. However, mitigation strategies could involve evacuating the impact zone and relocating critical infrastructure. Understanding the asteroid’s size, composition, and other characteristics is key to assessing the severity of the threat.
The sooner potential risks are detected, the better the chances of mitigating damage. NASA and the European Space Agency (ESA) have conducted tests to explore the feasibility of asteroid deflection. In the Double Asteroid Redirection Test (DART), a refrigerator-sized spacecraft intentionally collided with the asteroid Dimorphos to test the "kinetic impactor" technique, where an object is struck to alter its orbit. By nudging an asteroid early enough, even a small change in its velocity can significantly alter its path over time, preventing a collision.
The results of the DART mission will be confirmed by the Hera mission in December 2026, marking a key step in humanity's efforts to defend the planet from future asteroid threats.
