Today, ESA's Space Safety programme takes a significant step towards answering this question. The programme has been authorized to begin preliminary work on its next planetary defence mission, the Rapid Apophis Mission for Space Safety (Ramses).
Ramses aims to rendezvous with the asteroid 99942 Apophis and monitor it during its close but safe flyby of Earth in 2029. Scientists will study the asteroid as Earth's gravity affects its physical characteristics, enhancing our capability to protect our planet from similar threats in the future.
Apophis
The asteroid Apophis, roughly 375 meters in diameter-comparable to a cruise liner-will pass within 32,000 kilometers of Earth on April 13, 2029. This proximity will allow around two billion people across Europe, Africa, and parts of Asia to see it with the naked eye in clear, dark skies.
Astronomers have ruled out any risk of Apophis colliding with Earth for at least the next century. However, its 2029 flyby is a rare event. Large objects like Apophis come this close to Earth only once every 5,000 to 10,000 years. In comparison, a total solar eclipse occurs somewhere on Earth roughly every 18 months, and Halley's Comet reappears every 76 years.
The 2029 flyby of Apophis will captivate global attention, presenting a unique opportunity for scientific research, planetary defence, and public engagement.
Ramses
The Ramses spacecraft will meet Apophis before its Earth flyby and will monitor how Earth's gravity deforms and alters the asteroid. Patrick Michel, Director of Research at CNRS at Observatoire de la Cote d'Azur in Nice, explains: "There is still so much we have yet 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. For the first time ever, nature is bringing one to us and conducting the experiment itself. All we need to do is watch as Apophis is stretched and squeezed by strong tidal forces that may trigger landslides and other disturbances and reveal new material from beneath the surface."
To align with Apophis's approach, Ramses must launch by April 2028 and arrive by February 2029, two months before the flyby. ESA has received approval to start mission preparations immediately, utilizing existing resources. The final decision to fully commit to the mission will be made at ESA's Ministerial Council Meeting in November 2025.
Equipped with an array of scientific instruments, Ramses will conduct extensive pre- and post-flyby surveys of Apophis's shape, surface, orbit, rotation, and orientation. These studies will offer insights into the asteroid's response to gravitational forces and provide valuable data on its composition, structure, cohesion, mass, density, and porosity.
Understanding these properties is crucial for determining the best methods to deflect a hazardous asteroid. Additionally, as asteroids are remnants from the early Solar System, Ramses's findings will contribute to our knowledge of solar system formation and evolution.
Meanwhile, NASA has redirected its OSIRIS-REx spacecraft towards Apophis. Renamed OSIRIS-APEX, it will arrive about a month after Apophis's Earth flyby, furthering the scientific investigation of the asteroid's post-flyby state.
Researchers expect Earth's gravitational forces to alter Apophis's rotation and possibly cause surface quakes and landslides. With Ramses providing a detailed 'before and after' perspective, and OSIRIS-APEX conducting subsequent studies, scientists will gain comprehensive insights into the asteroid's transformations.
Rapid Reconnaissance: A Cornerstone for Planetary Defence
The collaboration between NASA's DART mission and ESA's Hera mission has shown that humanity can, in principle, redirect an asteroid. However, responding to an actual threat requires the capability to quickly deploy a reconnaissance mission.
Richard Moissl, head of ESA's Planetary Defence Office, states: "Ramses will demonstrate that humankind can deploy a reconnaissance mission to rendezvous with an incoming asteroid in just a few years. This type of mission is a cornerstone of humankind's response to a hazardous asteroid. A reconnaissance mission would be launched first to analyze the incoming asteroid's orbit and structure. The results would be used to determine how best to redirect the asteroid or to rule out non-impacts before an expensive deflector mission is developed."
Paolo Martino, leading ESA's Ramses effort, adds: "The Ramses mission concept reuses much of the technology, expertise and industrial and science communities developed for the Hera mission. Hera demonstrated how ESA and European industry can meet strict deadlines and Ramses will follow its example."
Related Links
Planetary Defence
Asteroid and Comet Mission News, Science and Technology
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