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When the cruise liner-sized asteroid comes 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 rocket can accompany asteroid Apophis before and after its safe, albeit rather close, flyby of Earth.
The 1,230-foot-diameter (375-meter) space rock will come closer to our planet 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 reach Apophis in February 2029, Ramses must launch in April 2028. According to the agency, preparatory work has already begun on the mission, using existing resources to meet this ambitious goal. However, the final decision to join the mission will be made at the ESA Ministerial Council 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 initially feared that a space rock might hit Earth between 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 the Study of Near-Earth Objects.
Scientists at the center use radar and telescopes to study near-Earth objects and understand the dangers they may pose to the planet. They keep a risk list and track asteroids with orbits that bring them close to our world – close enough to raise concerns about a possible impact.
While Apophis currently poses no danger, a close flyby presents a rare opportunity. 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 use this unique cosmic event to increase our understanding of what happens when space rocks interact with Earth’s gravity by studying Apophis from the closest possible location. 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 conduct experiments ourselves to interact with their surface,” said Patrick Michel, astrophysicist and director of research at the National Center for for scientific research in France, in a statement. “For the first time in history, nature is bringing us one and doing the experiment herself.”
Apophis is interesting because it is an S-type, or stony 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 approach before meeting Earth in 2029. The data ruled out any chance of an Earth impact 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 and iron.
Stony asteroids are part of the most common class of potentially dangerous asteroids that pose a threat to our planet. Understanding their composition and other details that can only be gleaned 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.
Ramses’ mission is unique because it would arrive at Apophis before the space rock passes our planet and then essentially cruise along to capture the sighting. This data could show astronomers how the asteroid is being altered by our planet’s gravity.
“All we have to do is watch Apophis being stretched and compressed by strong tidal forces that can trigger landslides and other disturbances and expose new material from below the surface,” Michel said.
The forces exerted by Earth’s gravity could also cause tremors on the asteroid.
The spacecraft will carry a suite of instruments to measure the asteroid’s shape, surface, orientation and orbit. Additionally, changes in the asteroid observed during the flyby could shed light on the composition, mass, density, porosity and internal structure of Apophis.
Tracking Apophis during and after its close approach to Earth could allow scientists to see if there are any shifts in its orbit that could affect the likelihood of it hitting Earth in the future, as well as any changes in the asteroid’s spin rate or its surface.
“Ramses will demonstrate that humanity can deploy a reconnaissance mission to rendezvous with an incoming asteroid within a few years,” Richard Moissl, head of ESA’s Planetary Defense Office, said in a statement. “This type of mission is the cornerstone of humanity’s response to a dangerous asteroid.” First, a reconnaissance mission would be launched to analyze the trajectory and structure of the incoming asteroid. The results would be used to determine how best to redirect the asteroid or rule out misses before a costly deflector mission is developed.
While Ramses still has 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, the two probes 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 probe spent seven years on a circumnavigation of the near-Earth asteroid Bennu, which included time spent exploring, landing and collecting a space rock sample.
The mission successfully delivered NASA’s first space-collected asteroid sample to Earth in September, and was given a new name to honor its new goal: Origins, Spectral Interpretation, Resource Identification and Security-APophis Explorer.
The spacecraft will not be able to collect a sample from Apophis because the sampling head was part of the Bennu sample capsule delivered to Earth. But OSIRIS-APEX will use its gas jets to try to kick up dust and small rocks on and below the surface of Apophis to study.
“Apophis offers a great opportunity to show the world the best of international cooperation with two missions involving different agencies working together on the best of science and planetary defense,” said Michel.
NASA and ESA have previously teamed up on other asteroid missions.
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. A historic test successfully changed the motion of a celestial object for the first time. None of the space rocks posed a threat to Earth, but the twin 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 in late 2026. Together with a pair of CubeSats, the mission will study the composition and mass of Dimorphos and how it was transformed by the impact, and determine how much momentum was transferred from the spacecraft to an asteroid.
“The Ramses mission concept reuses much of the technology, expertise and industrial and scientific communities developed for the Hera mission,” Paolo Martino, the Hera spacecraft manager 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 her lead.”