Are we safe? NASA tracking monster 1.5-km-wide asteroid heading towards earth

Recently scientists at NASA's Jet Propulsion Laboratory (JPL) in Southern California observed two asteroids as they passed close to Earth. One asteroid, found to have a small moon orbiting it, was accompanied by another that had been discovered only 13 days before its nearest approach to our planet. Despite no immediate threat from these near-Earth objects, the radar observations collected during their flybys will be instrumental for planetary defense and provide insights into their sizes, orbits, rotations, surface details, and composition, NASA said.

On June 27, the asteroid 2011 UL21 passed Earth at a distance of 4.1 million miles (6.6 million kilometers), about 17 times the distance between the Earth and the Moon. Initially discovered in 2011 by the NASA-funded Catalina Sky Survey in Tucson, Arizona, this was the first time it came close enough to Earth to be imaged by radar. Although nearly a mile wide (1.5 kilometers) and classified as potentially hazardous, future orbit calculations indicate it poses no threat to Earth in the foreseeable future, NASA scientists said.

Scientists utilized the Deep Space Network's 230-foot-wide (70-meter) Goldstone Solar System Radar near Barstow, California, to study these two asteroids. They transmitted radio waves to the asteroid and received the reflected signals with the same antenna. The data revealed that 2011 UL21 is roughly spherical and is a binary system, with a smaller asteroid or moonlet orbiting it at a distance of about 1.9 miles (3 kilometers). This discovery is significant because approximately two-thirds of asteroids of this size are binary systems. Understanding their mutual orbits, masses, and densities can provide key information about their formation.

Two days later, on June 29, the same team observed the asteroid 2024 MK as it passed Earth at a distance of only 184,000 miles (295,000 kilometers), slightly more than three-quarters of the distance to the Moon. Measuring about 500 feet (150 meters) in width, this asteroid appeared elongated and angular, with distinct flat and rounded areas. For this observation, scientists again used DSS-14 to transmit radio waves but received the returning signal using Goldstone's 114-foot (34-meter) DSS-13 antenna. This bistatic radar observation produced a detailed image of the asteroid's surface, revealing concavities, ridges, and boulders approximately 30 feet (10 meters) in size.

Close approaches of near-Earth objects the size of 2024 MK are relatively rare, occurring roughly every few decades. Hence, NASA scientists aimed to gather as much data as possible. The asteroid 2024 MK was first detected on June 16 by the NASA-funded Asteroid Terrestrial-impact Last Alert System (ATLAS) at the Sutherland Observing Station in South Africa. During its flyby, Earth's gravity altered its orbit, reducing its 3.3-year orbital period around the Sun by about 24 days. Although classified as potentially hazardous, future trajectory calculations show no threat to Earth for the foreseeable future.