All of us have a responsibility to protect our home planet. After all, it’s the only one we have, NASA Administrator Bill Nelson commented following the DART mission’s success in deflecting an asteroid. Those words are again applicable as NASA’s Jet Propulsion Laboratory monitors a cluster of plane-sized asteroids 2022 YS5, 2018 BY6, and 2025 ME92 that fly close to Earth this week.
The 95- to 204-foot-wide asteroid 2022 YS5 was closest to Earth at 4.15 million miles and traveling at a speed of about 13,600 miles per hour. Though seemingly far away, in astronomical terms, it is an eye-opener to our world’s vulnerability. These flybys, JPL’s Center for Near-Earth Object Studies (CNEOS) says, are routine; but every one is a valuable chance to refine tracking methods and learn about an asteroid’s makeup and orbit. Two others, 2018 BY6, around 210 feet in diameter, and 2025 ME92, 95 feet, will be flying by at 3.27 million and 3.19 million miles, respectively, this weekend.
The importance of such near passages is not merely that they are near but in the technical ability to find them. NASA’s NEOWISE mission that ended in 2024 after over ten years of infrared sky surveys cataloged over 44,000 objects in the solar system, of which more than 3,000 were near-Earth objects. Its replacement, the NEO Surveyor, will be launched no earlier than 2027 and is expected to discover asteroids that evade ground telescopes especially those approaching from the direction of the Sun or are low reflectivity.
On the ground, ground-based telescopes such as the future Rubin Observatory in Chile will be central. With its 8-meter mirror and 3.2-gigapixel camera, Rubin will take images of the full sky every three nights, allowing the quick identification and follow-up of potentially hazardous asteroids (PHAs) to sizes of 140 meters. Its data pipeline will gather on the order of 20 terabytes each night, correlating observations to piece together orbits and calculate impact probabilities.
But suppose a recently discovered asteroid seems to be harming Earth? The story of 2024 YR4 shows a glimpse into how complicated risk assessment is. Found in December 2024 by the ATLAS telescope in Chile, early orbital computations put it at 3.1 percent likelihood of striking Earth in 2032 the highest ever published for an object of its size or larger, NASA’s CNEOS says. This led to an official alert by the International Asteroid Warning Network. But following further observations that made it a more defined orbit, the threat had greatly diminished. As of the end of February 2025, the probability had dropped to 0.28 percent, and further inspection by the James Webb Space Telescope also attested that the object is “no significant impact risk to Earth in 2032 and beyond.”
The methodology involved in narrowing down impact probabilities is itself an engineering achievement. NASA’s Sentry impact monitoring system compares a variety of potential orbits for every NEO, charting them for a century and predicting probabilities of collision. As CNEOS manager Paul Chodas told Newsweek, “The ‘potentially hazardous’ designation simply means over many centuries and millennia the asteroid’s orbit may evolve into one that has a chance of impacting Earth. We do not assess these long-term, many-century possibilities of impact.” We do not evaluate these multi-century, long-term chances of impact.
Detection is but half the problem in planetary defense, the other half being intervention. The 2022 DART mission kinetic impactor test on Dimorphos was a breakthrough. By shortening the moonlet’s orbit around Didymos by 32 minutes, DART demonstrated it was possible to deflect an asteroid’s course key proof-of-concept for future deflection missions. “This result is one important step toward understanding the full effect of DART’s impact with its target asteroid,” said NASA Planetary Science Division director Lori Glaze.
The international network of telescopes, radar facilities, and space missions represents a multi-layered shield one that relies on advances in technology as well as collaboration among nations. With the NEO Surveyor and Rubin Observatory soon online, and planetary defense missions on the cusp of maturity, the capacity to detect, track, and, if required, deflect menacing asteroids stands on the verge of a new generation one characterized by watchfulness, information, and determination to accept whatever the universe serves up to us.
