In five years, as the asteroid Apophis - nicknamed the "God of Chaos" - passes close to Earth, scientists predict that the planet's gravity could trigger "astroquakes" on the asteroid's surface, potentially altering its appearance.
Since its discovery in 2004, Apophis has been closely tracked by astronomers. Initial calculations indicated a 2.7 per cent chance of impact in 2029, but updated models have reduced the risk to nearly zero, or one in two billion.
A team led by Ronald-Louis Ballouz, an asteroid scientist at Johns Hopkins University Applied Physics Laboratory, has examined the impact of Earth's gravity on Apophis, which will come within 19,000 miles of our planet. Their findings suggest that gravitational forces could produce intense tremors on Apophis, akin to earthquakes, as it makes its close approach.
Scheduled to pass by Earth on April 13, 2029, Apophis is a massive "city-killer," roughly the size of the Empire State Building. If it were to collide with Earth, the impact would unleash energy equivalent to multiple nuclear bombs, causing widespread destruction over hundreds of miles. Though Earth is safe from an impact in the near future, Apophis will still be classified as a "potentially hazardous" object and visible to the naked eye as it moves within geostationary orbit.
Apophis, measuring 1,230 feet in length, is named after Apep, the Egyptian god of darkness and disorder. Asteroids like Apophis typically have weathered surfaces from meteoroid impacts, a process known as space weathering. However, scientists have observed that asteroids passing close to planets often appear less weathered.
Ballouz's team theorizes that Earth's gravity might strip the outer layers from such asteroids. They used computational models to simulate Apophis's flyby, predicting that gravitational tidal forces could cause tremors beginning about an hour before the asteroid's closest approach. These shakes may dislodge rocks and even eject boulders into space. Earth's gravity might also alter Apophis's rotation, disrupting its tumbling motion and potentially triggering landslides over millennia, revealing fresh surface layers.
The study, published on the arXiv preprint database and accepted for publication in the Planetary Science Journal, suggests that Earth's gravity could gradually reshape Apophis, which is estimated to be four billion years old.
NASA's OSIRIS-APEX mission, scheduled to rendezvous with Apophis during its 2029 flyby, will closely study any changes the asteroid undergoes due to Earth's gravity. Additionally, NASA's Planetary Defense Coordination Office is developing strategies to deflect or destroy hazardous asteroids in the future, safeguarding Earth from potential "city-killer" impacts.
