NASA/JPL-Caltech
NASA’s Goldstone Solar System Radar recently observed asteroid 2024 MK, which made its closest approach to Earth on June 29.
Sign up for CNN’s Wonder Theory science newsletter. Explore the universe with news of fascinating discoveries, scientific breakthroughs and more.
CNN
—
When NASA scientists recently tracked the orbits of two space rocks as they neared Earth, they discovered a surprise: One of the asteroids has a small moon.
Astronomers regularly track the trajectories of asteroids to make sure none are on a potential collision course with our planet.
Although none of the recent asteroids have blown far, space rocks can provide valuable information that NASA uses to prepare for potential future collision scenarios.
Asteroids, which are remnants left over from the formation of the solar system, are also of interest because capturing details about their size, orbit and composition can reveal insights about our corner of the cosmos.
Astronomers at NASA’s Jet Propulsion Laboratory, located in Pasadena, California, used something called planetary radar through the Deep Space Network to track and image the asteroids.
The Deep Space Network is a system of radio antennas on Earth that helps the agency communicate with spacecraft exploring our solar system and releases radio waves to act as radar in space.
The first space rock, asteroid 2011 UL21, flew past Earth on June 27 at a distance of 4.1 million miles (6.6 million kilometers), or 17 times the distance between Earth and the Moon. Researchers first discovered the asteroid in 2011 using the Catalina Sky Survey in Tucson, Arizona. But since the space rock was first spotted, its flyby of Earth in June was the closest approach to our planet that radar has recorded.
Astronomers beamed radio waves from the 230-foot-wide (70-meter) Goldstone solar system radar satellite dish near Barstow, California, to the space rock. The waves bounced off the asteroid and bounced back to the antenna on the network satellite dish.
Researchers have classified the nearly mile-wide (1.5 kilometer) asteroid as potentially hazardous, meaning it has a chance of impacting Earth in the future. But astronomers don’t think it will pose a threat to our planet in the foreseeable future after calculating its future orbits and determining it won’t come too close to Earth.
Radar images show that the asteroid is roughly spherical and is one of a pair called a binary system. The space rock has a small moon orbiting it from a distance of 1.9 miles (3 kilometers).
NASA/JPL-Caltech
Seven radar observations show the one-kilometer-wide asteroid 2011 UL21 during its close approach to Earth on June 27 from about 4 million miles away. The asteroid and its small moon are circled in white.
“About two-thirds of asteroids of this size are thought to be binary systems, and their discovery is particularly important because we can use measurements of their relative positions to estimate their relative orbits, masses and densities, which provide key information about how they might have formed,” Lance Benner, JPL’s principal scientist who led the observations, said in a statement.
NASA missions, including the Lucy spacecraft, which will explore a mysterious population of space rocks called Trojans later this decade, have helped reveal how many moons exist around asteroids in our solar system.
And the DART mission intentionally crashed into a lunar moon called Dimorphos, which is orbiting a larger asteroid called Didymos, to alter the motion of a celestial body in space for the first time as a way to test asteroid deflection technology in 2022.
Sometimes astronomers don’t know an asteroid is in an orbit that brings it close to Earth until it approaches. This uncertainty is part of the reason NASA is increasing its efforts to better understand the population of asteroids closest to our world.
Researchers discovered asteroid 2024 MK just 13 days before it flew past Earth, flying just 184,000 miles (295,000 kilometers) from our planet — just over three-quarters of the distance between Earth and the Moon — on June 29.
NASA/JPL-Caltech
A mosaic shows 2024 MK as the asteroid rotates in one-minute increments about 16 hours after its closest approach to Earth.
The Asteroid Impact Last Warning System, or ATLAS, at the Sutherland Observatory in South Africa first spotted the space rock on June 16. Although also considered potentially dangerous, the asteroid does not appear to be on an alarming trajectory with respect to Earth anytime soon.
Astronomers sent radio waves to the space rock and captured a detailed image of asteroid 2024 MK. Its surface is littered with boulders thirty feet (10 meters) wide, as well as sunken spots and ridges. The asteroid is 500 feet (150 meters) wide and appears angular and elongated, while also having some prominent flat and rounded areas.
When the space rock passed by our planet and collided with Earth’s gravity, its orbit changed. Now, the asteroid’s 3.3-year trip around the sun has been shortened by about 24 days.
Objects the size of asteroid 2024 MK approach Earth only every few decades, so astronomers collected as much data as possible.
“This was an outstanding opportunity to study the physical properties and obtain detailed images of a near-Earth asteroid,” Benner said.
