Spacecraft will monitor the passage of an asteroid close to Earth; understand

When an asteroid the size of a cruise ship comes within 20,000 miles of Earth on April 13, 2029, it won’t be alone.

The European Space Agency (ESA) announced that its new spacecraft Ramses could follow the asteroid Apophis before and after its safe, although quite close, passage through Earth.

The space rock, which measures 375 meters in diameter, 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 of people in much of Europe, Africa and parts of Asia.

To reach Apophis in February 2029, Ramses is expected to launch in April 2028. Preparatory work has already begun on the mission using existing resources to achieve this ambitious goal, according to the agency. But the final decision on commitment to the mission will take place 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. Initially, astronomers were concerned about the possibility of the space rock impacting Earth in 2029 and 2068, but subsequent observations ruled out any risk of Apophis posing a threat to Earth in the next century, according to the Center for Near-Earth Object Studies. NASA (United States space agency).

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 cause concern about a possible impact.

Although Apophis currently poses no danger, the nearby passage presents a rare opportunity. Astronomers believe that an asteroid of this size comes so 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 increase our understanding of what happens when space rocks interact with Earth’s gravity, studying Apophis from the closest possible vantage point. Each agency will send a spacecraft to fly and follow the asteroid.

“There is still a lot we need to learn about asteroids, but so far we have had to travel to the bottom of the Solar system to study them and carry out experiments ourselves to interact with their surface,” said Patrick Michel, astrophysicist and director of research at the French National Center for Scientific Research, in a statement. “For the first time, nature is bringing one to us and carrying out the experiment on its own.”

Up close with a rocky asteroid

Apophis is of interest because it is a type S, or rocky, asteroid — unlike other space rocks visited by NASA missions, including Bennu, which is a type C, or carbonaceous, asteroid.

C-type asteroids are composed of clay and silicate rocks, while S-type asteroids are composed of silicate and nickel-iron materials.

Rocky 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 obtained through a close pass can help space agencies determine how best to deflect such asteroids if they are 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 track its trajectory to capture observations. This data could show astronomers how the asteroid is altered by our planet’s gravity.

“All we need to do is watch as Apophis is stretched and compressed by strong tidal forces that can trigger landslides and other disturbances, revealing new material beneath the surface,” Michel said.

The forces exerted by Earth’s gravity could also trigger earthquakes on the asteroid.

The spacecraft would carry a suite of instruments to measure the asteroid’s shape, surface, orientation and orbit. Furthermore, changes observed in the asteroid during its close pass could shed light on Apophis’ composition, mass, density, porosity, and internal structure.

Monitoring Apophis during and after its approach to Earth could allow scientists to see if there are changes to its orbit that could affect the likelihood of it hitting Earth in the future, as well as any changes to the asteroid’s rotation rate or its surface.

“Ramses will demonstrate that humanity can deploy a reconnaissance mission to rendezvous with an approaching asteroid in just a few years,” Richard Moissl, head of ESA’s Office for Planetary Defense, said in a statement. “This type of mission is a milestone in humanity’s response to a dangerous asteroid. A reconnaissance mission would be launched first to analyze the orbit and structure of the approaching asteroid. The results would be used to determine how best to redirect the asteroid or rule out impacts before an expensive deflection mission is developed.”

When spaceships come together

While Ramses still needs to be designed, built and ultimately approved by ESA next year, NASA’s OSIRIS-APEX mission, formerly known as OSIRIS-REx, is scheduled to reach the asteroid shortly after its closest approach to Earth. Together, both spacecraft can collect valuable data that captures a complete picture of how Apophis will change in response to its proximity to Earth.

As OSIRIS-REx, the spacecraft spent seven years on a round trip to the near-Earth asteroid Bennu, which included time spent surveying, landing 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 to honor its new target: Origins, Spectral Interpretation, Resource 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 to try to lift dust and small rocks both on the surface of Apophis and below to study them.

“Apophis offers a great occasion to show the world the best of international cooperation, with two missions involving different agencies working together for the best of science and planetary defense,” said Michel.

NASA and ESA have teamed up on other asteroid missions before.

In September 2022, NASA’s DART mission intentionally crashed a spacecraft into Dimorphos, an asteroid satellite orbiting a larger 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 double asteroid system was a perfect target to test deflection technology, as Dimorphos’ 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 pair of asteroids in late 2026. Along with a pair of CubeSats, the mission will study the composition and mass of Dimorphos and how it was transformed by the impact, in addition to determining 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,” said Paolo Martino, spacecraft manager at Hera who will also work on the Ramses mission, in a statement. “Hera has demonstrated how ESA and European industry can meet strict deadlines, and Ramses will follow suit.”

NASA mission reveals details about asteroid that could collide with Earth