In 2029, Earth is set to have a close encounter with a 375m-wide asteroid known as Apophis, and the European Space Agency intends to send a spacecraft to follow the hurtling spacerock as it flies by our planet.
ESA has confirmed preparatory work will begin for the Rapid Apophis Mission for Space Safety (Ramses), with a decision on whether the mission will go ahead to be made in November 2025.
Ramses would rendezvous with the asteroid - full name 99942 Apophis - and follow it as it zips by Earth at a distance of just 32,000km (19,900 miles) on 13 April 2029.
The Ramses spacecraft will provide scientists on the ground with data, including revealing how Earth's gravity alters the asteroid's characteristics.
ESA says the mission is part of its planetary defence programme, and findings could improve our ability to protect Earth from similar objects that are on course for impact.
Apophis and its near miss
The number of impact craters across the Solar System shows just how chaotic a place it can be.
And while the chances of Earth being hit by an asteroid of a significant size are slim, planetary defence remains a key concern for the space industry.
Astronomers say there's no cause for alarm: Apophis will miss Earth, and there's no chance of it colliding with our planet for at least the next 100 years.
But it will fly close by.
Around two billion people across Europe and Africa and parts of Asia may be able to see Apophis with the naked eye under good conditions, when it makes its close approach.
Astronomers say an asteroid this large comes this close to Earth just once every 5,000 to 10,000 years, making this an ideal chance to study one.
Ramses and the spacerock rendezvous
Being able to calculate the trajectory of an asteroid like Apophis and predict when and where it will fly by Earth is one thing, but imagine being able to send a spacecraft to rendezvous with the spacerock and follow it on its journey.
That's what Ramses will do, should everything go to plan.
"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," says Patrick Michel, Director of Research at CNRS at Observatoire de la Côte d'Azur in Nice.
"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."
Ramses needs to launch in April 2028 to make sure it can arrive at Apophis in February 2029, two months before its close approach with Earth.
Permission to begin preparatory work on the mission has been granted, and the decision whether to commit to the mission in full is due to be made at ESA’s Ministerial Council meeting in November 2025.
How Ramses will study Apophis
Ramses will analyse asteroid Apophis before and after its flyby of Earth, taking note of the asteroid's shape, surface, orbit, rotation and orientation.
It is expected to reveal how the asteroid is affected by external forces, such as the pull of Earth's gravity, in terms of its composition, interior structure, cohesion, mass, density and porosity.
"These are all very important properties for assessing how best to knock a hazardous asteroid off a collision course with Earth," a statement from ESA says.
"As asteroids are also time capsules formed over four billion years ago, data from Ramses will offer new scientific insights into the formation and evolution of the Solar System."
OSIRIS-APEX
Spacerock fans will remember the excitement surrounding the OSIRIS-REx mission, which returned a sample of asteroid Bennu to Earth in September 2023.
Now renamed OSIRIS-APEX, that spacecraft will join Ramses at the Apophis rendezvous, arriving one month after the asteroid's close encounter with Earth.
It's expected to enable additional data to be collected, and the measurement of longer-term effects on the asteroid.
The Ramses mission also recalls recent planetary defence investigations like NASA's DART mission and ESA's Hera mission, all forming a bigger picture as to humankind's ability to detect and deflect potentially hazardous spacerocks on a collision course with Earth.
"Ramses will demonstrate that humankind can deploy a reconnaissance mission to rendezvous with an incoming asteroid in just a few years," says Richard Moissl, head of ESA's Planetary Defence Office.
"This type of mission is a cornerstone of humankind’s response to a hazardous asteroid. A reconnaissance mission would be launched first to analyse 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."
"The Ramses mission concept reuses much of the technology, expertise and industrial and science communities developed for the Hera mission," says Paolo Martino, leader of the Ramses mission.
"Hera demonstrated how ESA and European industry can meet strict deadlines and Ramses will follow its example."
