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When a cruise-line-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 spacecraft can accompany asteroid Apophis before and after its safe, albeit fairly close, pass by Earth.
The space rock, measuring 1,230 feet (375 meters), 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 with the naked eye to about 2 billion people living in most of Europe, Africa and parts of Asia.
To reach Apophis in February 2029, Ramses should launch in April 2028. Preparatory work has already begun on the mission using existing resources to meet this ambitious goal, according to the agency. But the final decision on mission commitment will be made at the ESA Ministerial Council meeting in November 2025.
First discovered in 2004, Apophis is named for 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 impact Earth in 2029 and 2068, but subsequent observations have ruled out any risk of Apophis posing a threat to Earth for the next century, according to NASA’s Center for Object Studies Close to Earth.
Scientists at the center use radars and telescopes to study near-Earth objects and understand the dangers they may pose to the planet. They maintain a hazard list, tracking asteroids with orbits that bring them close to our world – close enough to cause concern about a possible impact.
While Apophis currently poses no danger, a close flyby presents a rare opportunity. Astronomers think that an asteroid this large comes in such close proximity to Earth only once every 5,000 to 10,000 years.
ESA and NASA plan to take advantage of 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 point possible. 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 Scientific Research in France, in a statement. “For the first time ever, nature is bringing one to us and performing the experiment itself.”
Apophis is of interest because it is an S-type, or stony, asteroid, unlike other space rocks visited by NASA missions, including Bennu, which is a C-type, or carbonaceous, asteroid.
C-type asteroids are composed of clay and silicate rocks, while S-types are composed of silicate and nickel-iron materials.
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 would arrive at Apophis before the space rock passes our planet and then essentially travel to capture observations. This data can tell astronomers how the asteroid is altered by our planet’s gravity.
“All we have to do is watch how Apophis is stretched and squeezed by strong tidal forces that can cause landslides and other disturbances and reveal new material from below the surface,” Michel said.
The forces exerted by Earth’s gravity can also cause earthquakes on asteroids.
The spacecraft would carry a series of instruments to measure the asteroid’s shape, surface, orientation and orbit. Additionally, changes in the asteroid observed during the flyby may shed light on the composition, mass, density, porosity and internal structure of Apophis.
Observing 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 the rate of the asteroid’s rotation or on its surface.
“Ramses will demonstrate that humanity can deploy a reconnaissance mission to rendezvous with an incoming asteroid in just a few years,” Richard Moissl, head of ESA’s Planetary Defense Office, said in a statement. “This type of mission is a cornerstone of humanity’s response to a dangerous asteroid. First a reconnaissance mission would be launched to analyze the orbit and structure of the incoming asteroid. The results will be used to determine how best to redirect the asteroid or rule out non-impacts before an expensive deflector mission is conducted.
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 capture the asteroid shortly after its close approach to The earth. Together, the two spacecraft can gather valuable data that captures a complete portrait of how Apophis will change in response to close contact with Earth.
As OSIRIS-REx, the spacecraft spent seven years on a round trip to the near-Earth asteroid Bennu, which included time spent observing, touching and collecting a sample of the space rock.
The mission successfully sent NASA’s first space-collected asteroid sample back to Earth in September, and received a new name to honor its new objective: Origin, Spectral Interpretation, Source Identification, and Security—APophis Explorer.
The spacecraft will not be able to collect a sample from Apophis because the sample collection head was included in the capsule with the Bennu sample delivered to Earth. But OSIRIS-APEX will use its gas thrusters in an attempt to remove dust and small rocks both on and below the surface of Apophis to study them.
“Apophis provides 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,” said Michel.
NASA and ESA have teamed up on other asteroid missions before.
In September 2022, NASA’s DART mission intentionally rammed a spacecraft into Dimorphos, an asteroid with a moon orbiting 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 two-asteroid system was a perfect target to test deflection technology because Dimorpho’s size is comparable 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 asteroid pair near the end of 2026. Along with a pair of CubeSats, the mission will study Dimorpho’s composition and mass and how it was transformed by the impact and determine how much momentum was transferred from the spacecraft to the asteroid.
“The Ramses mission concept reuses 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 demonstrated how ESA and European industry can meet tight deadlines and Ramses will follow suit.”