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By European Space Agency
Asteroid 2024 YR4 made headlines earlier this year when its probability of impacting Earth in 2032 rose as high as 3%. While an Earth impact has now been ruled out, the asteroid’s story continues.
The final glimpse of the asteroid as it faded out of view of humankind’s most powerful telescopes left it with a 4% chance of colliding with the Moon on 22 December 2032.
The likelihood of a lunar impact will now remain stable until the asteroid returns to view in mid-2028. In this FAQ, find out why we are left with this lingering uncertainty and how ESA's planned NEOMIR space telescope will help us avoid similar situations in the future.
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By NASA
5 min read
NASA Launching Rockets Into Radio-Disrupting Clouds
NASA is launching rockets from a remote Pacific island to study mysterious, high-altitude cloud-like structures that can disrupt critical communication systems. The mission, called Sporadic-E ElectroDynamics, or SEED, opens its three-week launch window from Kwajalein Atoll in the Marshall Islands on Friday, June 13.
The atmospheric features SEED is studying are known as Sporadic-E layers, and they create a host of problems for radio communications. When they are present, air traffic controllers and marine radio users may pick up signals from unusually distant regions, mistaking them for nearby sources. Military operators using radar to see beyond the horizon may detect false targets — nicknamed “ghosts” — or receive garbled signals that are tricky to decipher. Sporadic-E layers are constantly forming, moving, and dissipating, so these disruptions can be difficult to anticipate.
An animated illustration depicts Sporadic-E layers forming in the lower portions of the ionosphere, causing radio signals to reflect back to Earth before reaching higher layers of the ionosphere. NASA’s Goddard Space Flight Center/Conceptual Image Lab Sporadic-E layers form in the ionosphere, a layer of Earth’s atmosphere that stretches from about 40 to 600 miles (60 to 1,000 kilometers) above sea level. Home to the International Space Station and most Earth-orbiting satellites, the ionosphere is also where we see the greatest impacts of space weather. Primarily driven by the Sun, space weather causes myriad problems for our communications with satellites and between ground systems. A better understanding of the ionosphere is key to keeping critical infrastructure running smoothly.
The ionosphere is named for the charged particles, or ions, that reside there. Some of these ions come from meteors, which burn up in the atmosphere and leave traces of ionized iron, magnesium, calcium, sodium, and potassium suspended in the sky. These “heavy metals” are more massive than the ionosphere’s typical residents and tend to sink to lower altitudes, below 90 miles (140 kilometers). Occasionally, they clump together to create dense clusters known as Sporadic-E layers.
The Perseids meteor shower peaks in mid-August. Meteors like these can deposit metals into Earth’s ionosphere that can help create cloud-like structures called Sporadic-E layers. NASA/Preston Dyches “These Sporadic-E layers are not visible to naked eye, and can only be seen by radars. In the radar plots, some layers appear like patchy and puffy clouds, while others spread out, similar to an overcast sky, which we call blanketing Sporadic-E layer” said Aroh Barjatya, the SEED mission’s principal investigator and a professor of engineering physics at Embry-Riddle Aeronautical University in Daytona Beach, Florida. The SEED team includes scientists from Embry-Riddle, Boston College in Massachusetts, and Clemson University in South Carolina.
“There’s a lot of interest in predicting these layers and understanding their dynamics because of how they interfere with communications,” Barjatya said.
A Mystery at the Equator
Scientists can explain Sporadic-E layers when they form at midlatitudes but not when they appear close to Earth’s equator — such as near Kwajalein Atoll, where the SEED mission will launch.
In the Northern and Southern Hemispheres, Sporadic-E layers can be thought of as particle traffic jams.
Think of ions in the atmosphere as miniature cars traveling single file in lanes defined by Earth’s magnetic field lines. These lanes connect Earth end to end — emerging near the South Pole, bowing around the equator, and plunging back into the North Pole.
A conceptual animation shows Earth’s magnetic field. The blue lines radiating from Earth represent the magnetic field lines that charged particles travel along. NASA’s Goddard Space Flight Center/Conceptual Image Lab At Earth’s midlatitudes, the field lines angle toward the ground, descending through atmospheric layers with varying wind speeds and directions. As the ions pass through these layers, they experience wind shear — turbulent gusts that cause their orderly line to clump together. These particle pileups form Sporadic-E layers.
But near the magnetic equator, this explanation doesn’t work. There, Earth’s magnetic field lines run parallel to the surface and do not intersect atmospheric layers with differing winds, so Sporadic-E layers shouldn’t form. Yet, they do — though less frequently.
“We’re launching from the closest place NASA can to the magnetic equator,” Barjatya said, “to study the physics that existing theory doesn’t fully explain.”
Taking to the Skies
To investigate, Barjatya developed SEED to study low-latitude Sporadic-E layers from the inside. The mission relies on sounding rockets — uncrewed suborbital spacecraft carrying scientific instruments. Their flights last only a few minutes but can be launched precisely at fleeting targets.
Beginning the night of June 13, Barjatya and his team will monitor ALTAIR (ARPA Long-Range Tracking and Instrumentation Radar), a high-powered, ground-based radar system at the launch site, for signs of developing Sporadic-E layers. When conditions are right, Barjatya will give the launch command. A few minutes later, the rocket will be in flight.
The SEED science team and mission management team in front of the ARPA Long-Range Tracking and Instrumentation Radar (ALTAIR). The SEED team will use ALTAIR to monitor the ionosphere for signs of Sporadic-E layers and time the launch. U.S. Army Space and Missile Defense Command On ascent, the rocket will release colorful vapor tracers. Ground-based cameras will track the tracers to measure wind patterns in three dimensions. Once inside the Sporadic-E layer, the rocket will deploy four subpayloads — miniature detectors that will measure particle density and magnetic field strength at multiple points. The data will be transmitted back to the ground as the rocket descends.
On another night during the launch window, the team will launch a second, nearly identical rocket to collect additional data under potentially different conditions.
Barjatya and his team will use the data to improve computer models of the ionosphere, aiming to explain how Sporadic-E layers form so close to the equator.
“Sporadic-E layers are part of a much larger, more complicated physical system that is home to space-based assets we rely on every day,” Barjatya said. “This launch gets us closer to understanding another key piece of Earth’s interface to space.”
By Miles Hatfield
NASA’s Goddard Space Flight Center, Greenbelt, Md.
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Heliophysics Goddard Space Flight Center Heliophysics Division Ionosphere Missions NASA Centers & Facilities NASA Directorates Science & Research Science Mission Directorate Sounding Rockets Sounding Rockets Program The Solar System The Sun Uncategorized Wallops Flight Facility Weather and Atmospheric Dynamics Explore More
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By European Space Agency
The European Space Agency’s (ESA) newest planetary defender has opened its ‘eye’ to the cosmos for the first time. The Flyeye telescope’s ‘first light’ marks the beginning of a new chapter in how we scan the skies for new near-Earth asteroids and comets.
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By NASA
The asteroid Donaldjohanson as seen by the Lucy Long-Range Reconnaissance Imager (L’LORRI). This is one of the most detailed images returned by NASA’s Lucy spacecraft during its flyby. This image was taken at 1:51 p.m. EDT (17:51 UTC), April 20, 2025, near closest approach, from a range of approximately 660 miles (1,100 km). The spacecraft’s closest approach distance was 600 miles (960 km), but the image shown was taken approximately 40 seconds beforehand. The image has been sharpened and processed to enhance contrast.NASA/Goddard/SwRI/Johns Hopkins APL/NOIRLab NASA’s Lucy spacecraft took this image of the main belt asteroid Donaldjohanson during its flyby on April 20, 2025, showing the elongated contact binary (an object formed when two smaller bodies collide). This was Lucy’s second flyby in the spacecraft’s 12-year mission.
Launched on Oct. 16, 2021, Lucy is the first space mission sent to explore a diverse population of small bodies known as the Jupiter Trojan asteroids. These remnants of our early solar system are trapped on stable orbits associated with – but not close to – the giant planet Jupiter. Lucy will explore a record-breaking number of asteroids, flying by three asteroids in the solar system’s main asteroid belt, and by eight Trojan asteroids that share an orbit around the Sun with Jupiter. April 20, 2025 marked Lucy’s second flyby. The spacecraft’s next target is Trojan asteroid Eurybates and its satellite Queta in Aug. 2027.
Lucy is named for a fossilized skeleton of a prehuman ancestor. This flyby marked the first time NASA sent a spacecraft to a planetary body named after a living person. Asteroid Donaldjohanson was unnamed before becoming a target. The name Donaldjohanson was chosen in honor of the paleoanthropologist who discovered the Lucy fossil, Dr. Donald Johanson.
Learn more about Lucy’s flyby of asteroid Donaldjohanson.
Image credit: NASA/Goddard/SwRI/Johns Hopkins APL/NOIRLab
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