Ramses: Europe takes the lead in planetary defense

The Ramses mission to the asteroid Apophis is expected to launch in 2028. It will be the cornerstone of an ESA planetary defense program, designed to protect our planet from the risk of collision with near-Earth objects.

The countdown has begun for the launch, in early 2028, of the European Space Agency’s (ESA) new scientific mission.

The aim of the project, led by ESA in collaboration with the Japanese space agency JAXA, is to study one of the most anticipated astronomical events of the next decade: the extremely close passage of the asteroid by Earth, on Friday, April 13, 2029.

On that day, the “” will pass by our planet at a minimum distance of only 31,600 km, lower than the altitude of the satellites of telecommunications in geostationary orbit, located approximately 36,000 km.

It is unprecedented meeting will not go unnoticed. Apophis will be visible to the naked eye across much of Europe and Africa, allowing more than two billion people to observe it, as long as the night sky is clear, notes .

In addition to being spectacular, “this passage through Earth is also a crucial natural experience, which will help improve our planet’s defenses against asteroids that could hit it”, explains Patrick Michelastrophysicist at the JL Lagrange laboratory in Nice, and principal investigator of the new mission.

A first mission

For a long time confined to , preventive measures against the risk of collision between our planet and an asteroid have now become reality.

ESA has been developing its Space Security Program since 2019, part of which is dedicated to forecasting and preventing impacts of asteroids. The objective is to monitor and study potentially dangerous bodies and devise strategies capable of warding off these threats.

The program already has a first mission: a Hera. Launched in 2024, it will serve as a full-scale test of the deflection of the asteroid, located about 11 million kilometers from Earth, caused by NASA’s . Ramses is the second mission of the show.

In addition to Ramses, NASA’s OSIRIS mission also scheduled a meeting with Apophis. The OSIRIS-Rex probe, which went to visit the asteroid Bennu, wasted no time, and — now named .

An asteroid the size of the Eiffel Tower

Apophis is a near-Earth object, an asteroid whose orbit around the Sun occasionally crosses Earth’s orbit.

“Objects of this type could potentially collide with our planet”, he states Benoit Carryassistant astronomer and asteroid specialist at the Observatoire de la Côte d’Azur, also in Nice.

Other distinctive feature of Apophis is the fact that it is a relatively large asteroid. It has about 330 meters in diameterequivalent to the height of the Eiffel Tower, and an estimated mass of between 40 and 50 million tons.

“The approach of such a large body to our planet is an event rare, only occurring once every few thousand years”, emphasizes the astronomer. Furthermore, Apophis travels at a very high speed: about 12 km per second.

If such an object were to hit Earth, “it would form a crater eight to ten times its own size, that is, about 2.5 km in diameter”, explica Carry.

“It would be enough to cause a major catastrophe if it hit an urban area, or a devastating tsunami if it hit the ocean. Not to mention the enormous amount of dust that would be projected into the atmosphere and cause climate cooling.”

According to Michel, “the damage would be on the scale of an entire country”.

“A unique scientific opportunity”

Shortly after Apophis was discovered in 2004 by researchers at the University of Hawaii, in the USA, who specialized in the study of asteroids, astronomers calculated that there was a probability of 1 in 37, or 2.7%of the asteroid hitting Earth in 2029.

He was “the highest probability of collision ever estimated to an asteroid,” says Carry, reason why it was named Apophisthe Egyptian god of chaos and destruction.

Fortunately, in the following weeks, more accurate observations and calculations eliminated any risk of collision of the asteroid, not just in 2029, but also for at least another century.

Thus, if the very close passage of Apophis to Earth in 2029 no longer poses a danger, why study it?

“Because it offers us a unique scientific opportunity to better understand the physical properties of the asteroid (its mass, density, porosity, internal structure, among others) and the way they evolve as a result of the Earth’s gravitational attraction”, explains Michel.

In fact, investigators hope that when the two bodies are very close, the tidal forces caused by Earth’s gravity stretch and I will crush you, O Apophis.

This could trigger landslides on the asteroid’s surfaceor even internal vibrations. Furthermore, its orbit and rotation period are expected to undergo slight changes.

“In addition to improving our understanding of asteroids, studying the properties and behavior of Apophis at its closest point to Earth could also help to define the best strategies to neutralize these potentially dangerous objects”, adds Michel.

“For example, measuring its response to external forces, in this case represented by the Earth’s tidal forces,— and determining its degree of porosity, that is, realizing whether its interior contains a lot of empty space or notwill help you calculate the force required to hit a similar body and deflect it effectively from the Earth’s trajectory.”

In practice, the mission will be based on a spaceship 2 meters widewhose design will be inspired by that of the Hera probe.

“Like Hera, Ramses will be composed of a main ship and 2 miniaturized satellites cubesateach weighing 12 kilos, one of which will be placed near Apophis, while the other will land on the asteroid”, explains Michel.

To achieve its objectives, Ramses will transport various instruments. One of them is a hyperspectral cameracapable of capturing images using a large number of adjacent spectral bands, which will make it possible to determine the chemical composition of the asteroid.

Also a plasma spectrometer will analyze the environment of charged particles around the asteroid, associated with its passage through the Earth’s magnetosphere, the region of space under the influence of our planet’s magnetic field.

The cubesat designed to be placed near Apophis will carry a dust detector and analyzer capable of determine its chemical compositionas well as a low-frequency radar, which will probe the interior of the asteroid.

The cubesat destined to land on the asteroid will be equipped with a gravimeter, to measure your gravitational fieldand with a seismograph, to analyze the propagation of seismic waves and reveal the internal structure of this celestial body.

NASA’s DART mission has already demonstrated that it is on a potential collision course with Earth. ESA’s Ramses will now try to determine whether, and how, we could do this with a monumental celestial body, such as the “Chaos Asteroid”.