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When a cruise liner-sized asteroid approaches within 19,883 miles (32,000 kilometers) of Earth on April 13, 2029, it won’t be alone.
The European Space Agency has announced that its new Ramses spacecraft can accompany asteroid Apophis before and after its safe, albeit fairly close, pass by Earth.
The 1,230-foot (375-meter) space rock will approach our planet closer than the satellites in its orbit and 10 times closer than the Moon. Apophis will come so close to Earth that it will be visible to the naked eye for about 2 billion people living in most of Europe, Africa and parts of Asia.
To arrive at Apophis in February 2029, Ramses is due to launch in April 2028. Preparatory work on the mission has already begun, using existing resources to achieve this ambitious goal, according to the agency. But the final decision to commit to the mission will be made at the ESA Council of Ministers meeting in November 2025.
First discovered in 2004, Apophis is named after the Egyptian god of chaos and darkness and is believed to be shaped like a peanut. Astronomers were initially concerned that the space rock could hit Earth in 2029 and 2068, but subsequent observations have ruled out any risk of Apophis posing a threat to Earth in the next century, according to NASA’s Center for Near-Earth Object Studies.
Scientists at the center use radar and telescopes to study near-Earth objects and understand the dangers they may pose to the planet. They maintain a risk list, tracking asteroids with orbits that bring them close to our world — close enough to raise concerns about a potential impact.
While Apophis currently poses no threat, a close flyby presents a rare possibility. Astronomers believe that an asteroid this large comes this close to Earth only once every 5,000 to 10,000 years.
ESA and NASA plan to take advantage of this unique cosmic event to improve our understanding of what happens when space rocks interact with Earth’s gravity by studying Apophis from the closest possible vantage point. Each agency will send a spacecraft to fly by and track the asteroid.
“There is still so much to learn about asteroids, but until now we have had to travel deep into the solar system to study them and perform experiments ourselves to interact with their surface,” said Patrick Michel, astrophysicist and director of research at the National Center for Scientific Research in France, in a statement. “For the first time, nature brings us one and conducts the experiment herself.”
Apophis is of interest because it is an S-type, or rocky, asteroid—different from other space rocks visited by NASA missions, including Bennu, which is a C-type, or carbonaceous asteroid.
NSF/AUI/GBO/JPL-Caltech/NASA
These images represent radar observations of Apophis on March 8, 9, and 10, 2021, when it made its last close approach before its encounter with Earth in 2029. The data rule out any chance of an impact on Earth for at least a century.
C-type asteroids are made of clay and silicate rocks, while S-type asteroids are composed of silicate materials and nickel-iron.
Stony asteroids are part of the most common class of potentially hazardous asteroids that pose a threat to our planet. Understanding their composition and other details that can only be obtained from a close flyby could help space agencies determine how best to deflect such asteroids if they are predicted to be on a collision course with Earth.
The Ramses mission is unique because it will arrive at Apophis before the space rock passes our planet and then essentially ride around to capture observations. This data could show astronomers how the asteroid is modified by our planet’s gravity.
“All we have to do is watch Apophis being stretched and squeezed by strong tidal forces that can trigger landslides and other disturbances and expose new material below the surface,” Michel said.
The forces exerted by Earth’s gravity can also cause earthquakes on the asteroid.
The spacecraft will carry a suite of instruments to measure the shape, surface, orientation and orbit of the asteroid. Additionally, changes in the asteroid observed during the flyby could shed light on Apophis’ composition, mass, density, porosity and internal structure.
Tracking Apophis during and after its close approach to Earth could allow scientists to see if there are any changes in its orbit that could affect the likelihood of it hitting Earth in the future, as well as any changes in its spin rate. the asteroid or to its surface.
“Ramses will demonstrate that humanity can deploy a reconnaissance mission to rendezvous with an approaching asteroid in just a few years,” Richard Moisel, head of ESA’s Planetary Defense Office, said in a statement. “This type of mission is a milestone in humanity’s response to a dangerous asteroid. First, a reconnaissance mission will be launched to analyze the orbit and structure of the approaching asteroid. The results will be used to determine how best to redirect the asteroid or rule out no-hits before an expensive deflector mission is developed.
While Ramses still needs to be designed, built and finally approved by ESA next year, NASA’s OSIRIS-APEX mission, formerly known as OSIRIS-REx, is on track to catch up with the asteroid just after its close approach to Earth. Together, both spacecraft can collect valuable data that captures a complete portrait of how Apophis will change in response to its close encounter with Earth.
As OSIRIS-REx, the spacecraft spent seven years on a round trip to the near-Earth asteroid Bennu, which included time spent exploring, touching and collecting a sample of the space rock.
The mission successfully delivered NASA’s first space-collected asteroid sample to Earth in September and was given a new name in honor of its new purpose: Origin, Spectral Interpretation, Resource Identification and Security—APophis Explorer.
The spacecraft will not be able to take a sample from Apophis because the sample collection head was included in the Bennu sample capsule delivered to Earth. But OSIRIS-APEX will use its gas thrusters in an attempt to lift dust and small rocks both on and below the surface of Apophis to study them.
“Apophis offers a great opportunity to show the world the best of international cooperation, with two missions involving different agencies working together for the best of science and planetary protection,” Michel said.
NASA and ESA have teamed up on other asteroid missions before.
In September 2022, NASA’s DART mission intentionally rammed a spacecraft into Dimorphos, a lunar asteroid that orbits a larger parent asteroid known as Didymos. The historic test successfully changed the motion of a celestial object for the first time. Neither space rock posed a threat to Earth, but the binary asteroid system was a perfect target for testing deflection technology, as Dimorphos is comparable in size to asteroids that could threaten our planet.
ESA’s Hera mission will launch a spacecraft in October on a journey to observe the aftermath of the DART impact, reaching the pair of asteroids near the end of 2026. Together with a pair of CubeSats, the mission will study the composition and mass of Dimorphos and how it has transformed from the impact and determine how much momentum was transferred from the spacecraft to the asteroid.
“The Ramses mission concept leverages much of the technology, expertise and industrial and scientific communities developed for the Hera mission,” Paolo Martino, spacecraft manager for Hera, who will also work on the Ramses mission, said in a statement. “Hera has demonstrated how ESA and European industry can meet tight deadlines and Ramses will follow suit.”
