When the possibly hazardous asteroid 99942 Apophis makes its breathtakingly shut flyby of Earth on April 13, 2029, greater than 2 billion individuals throughout Africa and Western Europe will be capable of watch it drift throughout the evening sky. Under clear skies, the house rock will seem as a faint star — about as vivid as the celebrities within the Big Dipper and simply seen to the unaided eye — gliding steadily overhead.
Apophis’ flyby will mark “the first time in space history that a potentially hazardous asteroid is visible to the naked eye,” Richard Binzel, a professor of planetary sciences at MIT, stated Monday (Sept. 8) throughout a keynote tackle on the Europlanet Science Congress in Helsinki, Finland. Astronomers estimate {that a} shut method by an asteroid this huge — 1,100 ft (340 meters) throughout, or roughly the peak of the Eiffel Tower — happens solely as soon as each 7,500 years.
For the general public, it is going to be a stunning, once-in-a-lifetime spectacle. For scientists, it guarantees one thing even rarer: a once-in-a-millennium pure experiment to observe in actual time how Earth’s gravity reshapes an enormous asteroid. “We don’t know,” Binzel stated, “and we won’t know until we look.”
Binzel, a pioneer in asteroid hazard analysis and the inventor of the Torino Impact Hazard Scale that’s used to rate impact risks of asteroids and comets, underscored one point above all: “If you take nothing else away from this talk, I want you to take away three things,” he said during his presentation. “Apophis will safely pass the Earth; Apophis will safely pass the Earth; Apophis will safely pass the Earth.”
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When Apophis was first discovered in 2004, however, the picture was far less certain. Early calculations suggested a 2.7% chance of impact on April 13, 2029, placing it at Level 4 on the Torino scale — the highest rating ever given to a near-Earth object. Scientists named the asteroid 99942 Apophis, after the Egyptian god of the underworld, earning it the nickname the “god of chaos” asteroid.
Over the next two decades, continuous tracking and radar observations narrowed Apophis’ orbit from hundreds of miles of uncertainty to just a few. By 2021, Apophis was formally removed from all risk lists, and scientists estimated it posed no threat for at least the next 100 years. In September last year, however, a study noted there is still a tiny possibility that an unknown asteroid could nudge it onto a collision path before its close Earth flyby in 2029. The odds are over one in a billion, and while scientists won’t be able to fully rule out this scenario for another three years, astronomers remain confident Apophis poses no danger for the next century.
“It’s been a lot of work by a lot of people to make sure we can say totally and confidently that Apophis will safely pass the Earth — absolutely no doubt,” Binzel said.
“Earth won’t care, but Apophis will”
While Earth itself will barely notice the encounter, Apophis will not leave unchanged. As it passes just over 18,600 miles (30,000 kilometers) above the planet’s surface — closer than geostationary satellites — its Aten-class orbit, which lies mostly inside Earth’s path around the sun and is thus often hidden in our star’s bright glare, will be reshaped into a wider Apollo-class trajectory. Its rotation may also shift, which might send the asteroid into a fresh tumbling state, Binzel said.
“The Earth won’t care, but Apophis will care, because Apophis’ orbit will change,” he said. “It’s all about the encounter physics.”
To capture those changes firsthand, NASA has reassigned its OSIRIS-REx spacecraft, fresh from its mission to the asteroid Bennu, to a new role as OSIRIS-APEX. The probe will rendezvous with Apophis before the flyby, mapping its surface, monitoring its spin, and measuring how Earth’s gravity alters the asteroid during its close pass. Among the most tantalizing goals, Binzel said, is the chance to measure seismic vibrations inside Apophis.
“In 60 years of planetary science, we’ve only measured seismicity for two objects: the moon and Mars,” he said. “This would be the opportunity for another leap forward in seismic measurements and interpretation of interior properties.”
That leap could come from the Rapid Apophis Mission for Space Safety (RAMSES). The European Space Agency (ESA) mission, if approved at ESA’s Ministerial Council in November, would launch in spring 2028 and arrive at the asteroid by February 2029. The mission’s goal would be to observe Apophis before, during and after its flyby of Earth, Monica Lazzarin, a professor of physics and astronomy on the University of Padua in Italy and a member of the RAMSES science staff, stated on the convention.
Hovering as shut as 3 miles (5 km) from the asteroid throughout its April 12-14, 2029, encounter, RAMSES would map Apophis’ orbit, seek for mud clouds raised by tidal forces, and probably deploy a small satellite tv for pc known as a cubesat to the touch the floor and detect seismic waves, Lazzarin stated.
Beyond science, Apophis is a proving floor for planetary protection, scientists say, as it’s going to help humanity’s effort to grasp and put together for the rare-but-real threat of an asteroid affect. While Apophis itself poses no hazard, it belongs to the category of near-Earth asteroids that might someday threaten our planet. By learning how Earth’s tidal forces reshape Apophis, scientists can refine the fashions that may be vital for deflecting a hazardous asteroid.
“Apophis is not a planetary defense emergency,” Tom Statler, a planetary scientist at NASA headquarters in Washington, D.C., added throughout a Q&A session on the convention. “It is an opportunity, and an unprecedented one.”
“Asteroids are not something to be scared of,” he added. “They’re something to understand — and that’s what we’re doing.”