Europe announces new mission to infamous asteroid Apophis
ESA’s Ramses spacecraft is due to scout both before and after the asteroid Apophis, which will approach Earth in 2029.
An artist’s rendering of ESA’s Rapid Apophis mission for space safety.
Asteroid Apophis is poised for a close-up look, but what about us? In 2029, this sizable space rock will come within one-tenth of the distance between Earth and the Moon. Scientists and engineers are currently racing against the clock to arrange a spacecraft rendezvous to observe this rare encounter first-hand.
The project, led by the European Space Agency (ESA), is called the Rapid Apophis Mission for Space Safety, or Ramses. Ramses must be launched by April 2028. The ambitious timeline comes as Ramses is not yet fully funded due to ESA budgeting issues, the agency said in a statement announcing the mission on July 16. But it also represents a historic opportunity. Ramses is scheduled to arrive at Apophis in February 2029, about two months after the asteroid will approach Earth. Scientists estimate that an object of this size comes close once every 7,500 years. The size is roughly the width of the Empire State Building.
“This is the first time in modern human history and the history of civilization that we’ve had an object this big come this close,” says Dani Dell’Agiustina, a planetary scientist at the University of Arizona and leader of another NASA mission that will reach Apophis later. During the approach, Earth’s gravity is expected to cause small and possibly large changes to the asteroid: Apophis will follow a slightly different orbit around the sun, its roughly 30-hour daylight hours will shorten or lengthen, and landslides and earthquakes could change its surface.
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Scientists began worrying about Apophis shortly after its discovery in 2004, when they realized the asteroid’s orbit indicated it might collide with Earth in 2029. Since then, careful study of the asteroid’s path around the Sun has determined that not only will the flyby in 2029 be harmless, but Earth will be safe from Apophis in the foreseeable future.
This is very good news. Apophis, with a diameter of about 1,100 feet (335 meters), would cause serious damage if it hit Earth. The most recent notable asteroid to hit Earth exploded over Chelyabinsk, Russia, in 2013, releasing the equivalent of about 440 kilotons of TNT and injuring more than 1,600 people. Scientists estimate that the asteroid was only 17 to 20 meters wide. In an earlier impact in 1908 (now known as the Tunguska event), the explosion of a 131-foot-wide asteroid flattened about 80 million trees over more than 2,000 square kilometers of remote Siberian soil.
While scientists can now safely remove Apophis from the list of apocalyptic threats currently facing humanity, they’re still not convinced that all other asteroids in Earth’s neighborhood are similarly benign, which is why planetary defense scientists are eager to use the 2029 flyby of Apophis as a once-in-a-millennium opportunity to learn about the space rock we’ve encountered so closely.
“Although an asteroid like Apophis impacting Earth is an extremely rare event, it’s better to be aware than to be caught off guard,” said Richard Binzel, a planetary scientist at the Massachusetts Institute of Technology who has been raising awareness of the scientific possibilities of the 2029 flyby for years.
NASA has already rescheduled the OSIRIS-REx mission to spend two years in orbit around Apophis, but the spacecraft won’t arrive until just after the close encounter. There’s a good excuse for the delay: It was the shortest possible time to get there after completing its primary mission last fall to deliver precious material to Earth from an asteroid called Bennu. (The mission, now named OSIRIS-APEX, is led by DellaGiustina.)
DellaGiustina and his colleagues are confident that they can use the mission’s data to reconstruct how the close approach affected Apophis. But a mission like Ramses, which aims to stay on Apophis for six months, starting two months before the approach, could provide valuable observations of the asteroid’s conditions before the approach. Ramses might even be able to provide images of the entire asteroid as it responds to Earth’s gravity, says Paolo Martino, an ESA engineer leading the Ramses mission. ESA also wants to equip the spacecraft with a small, deployable companion vehicle that could land on Apophis before the approach and provide a first-hand ground report.
Of course, that requires ESA to meet a tight schedule to build, test, and launch an ambitious interplanetary mission in less than four years. That’s possible because the Ramses spacecraft is essentially a twin of ESA’s Hera mission, with only minor modifications to its solar panels and fuel tanks, Martino says. Hera is scheduled to launch this fall to study the double asteroids Didymos and Dimorphos, which NASA explored with the Double Asteroid Redirection Test (DART) mission in 2022.
The connection between the two missions goes beyond spacecraft design. The DART mission tested whether humans could maneuver an asteroid in orbit to avoid a collision with Earth, if necessary — a key principle of planetary defense. The Ramses mission will test another aspect of the field: if humans discovered an asteroid on a collision trajectory with Earth, could they launch a spacecraft to scout the target fast enough to formulate an intervention mission. The observations that Ramses and OSIRIS-APEX will collect should also help scientists understand the structure of space rocks throughout the solar system — information that’s crucial for future doomsday avoidance missions.
