Sign up for CNN’s Wonder Theory science newsletter. Explore the universe with news about fascinating discoveries, scientific breakthroughs and more.
CNN
—
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 has announced that its new Ramses spacecraft could accompany the asteroid Apophis before and after its safe, yet relatively close, passage by Earth.
The space rock, which measures 375 meters in diameter, will approach our planet closer than orbiting satellites and ten times closer than the Moon. Apophis will come so close to Earth that it will be visible to 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 is scheduled to launch in April 2028. Preparatory work for the mission has already begun with existing resources to achieve this ambitious goal, according to the agency. But the final decision on whether to commit to the mission will be taken 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 thought to be shaped like a peanut. Astronomers initially feared the space rock would collide with Earth in 2029 and 2068, but subsequent observations have ruled out any risk that Apophis poses a threat to Earth in the next century, according to NASA’s Center for Near-Earth Object Studies.
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 risk list, tracking asteroids whose orbits bring them close enough to our planet to raise concerns about a potential impact.
Although Apophis currently poses no threat, its close flyby represents a rare opportunity. Astronomers estimate that an asteroid of this size comes 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 better understand 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.
“We still have a lot to learn about asteroids, but until now we have had to go deep into the solar system to study them and conduct experiments ourselves to interact with their surface,” Patrick Michel, an astrophysicist and research director at the French National Center for Scientific Research (CNRS), said in a statement. “For the first time, nature is bringing us one and conducting the experiment itself.”
Apophis is interesting 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-type asteroids are composed of silicate and nickel-iron materials.
Stony asteroids are among 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 through a close flyby could help space agencies determine the best way to deflect these asteroids if they are predicted to be on a collision course with Earth.
The Ramses mission is unique in that it would arrive at Apophis before the space rock passes our planet and then follow it to collect observations. This data could show astronomers how the asteroid is being changed by our planet’s gravity.
“All we have to do is watch Apophis stretch and compress under strong tidal forces that can trigger landslides and other disturbances and reveal new material beneath the surface,” Michel said.
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. In addition, changes observed on the asteroid during the flyby could shed light on Apophis’ composition, mass, density, porosity and interior structure.
Keeping an eye on 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 asteroid’s rotation speed or its surface.
“Ramses will demonstrate that humanity is capable of deploying a reconnaissance mission to reach an approaching asteroid in just a few years,” Richard Moissl, head of ESA’s Planetary Defence Office, said in a statement. “This type of mission is the cornerstone of humanity’s response to a hazardous asteroid. A reconnaissance mission would first be launched to analyse the orbit and structure of the approaching asteroid. The results would be used to determine how best to redirect the asteroid or rule out non-impacts before developing a costly deflector mission.”
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, the two probes can collect valuable data that paint a complete picture of how Apophis will evolve in response to its close approach to Earth.
Called OSIRIS-REx, the spacecraft spent seven years on a round-trip journey to the near-Earth asteroid Bennu, which included time spent studying, landing and collecting a sample of the space rock.
The mission successfully delivered NASA’s first asteroid sample collected in space to Earth in September and received a new name to honor its new focus: Origins, Spectral Interpretation, Resource Identification and Security-APophis Explorer.
The spacecraft won’t 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 kick up dust and small rocks on and below the surface of Apophis for study.
“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 defense,” Michel said.
NASA and ESA have previously collaborated on other asteroid missions.
In September 2022, NASA’s DART mission intentionally collided with a spacecraft called Dimorphos, a lunar asteroid orbiting a larger parent asteroid known as Didymos. This historic test successfully altered the motion of a celestial object for the first time. Neither asteroid posed a threat to Earth, but the double-asteroid system was a perfect target to test the deflection technology because Dimorphos is comparable in size to asteroids that could endanger our planet.
ESA’s Hera mission will launch a spacecraft in October to observe the aftermath of the DART impact, reaching the asteroid pair in late 2026. Using 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 the asteroid.
“The Ramses mission concept reuses much of the technology, expertise and industrial and scientific communities developed for the Hera mission,” Paolo Martino, 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 strict deadlines and Ramses will follow suit.”