The asteroid Apophis, named after the Egyptian god of chaos, is preparing for a close encounter with Earth on April 13, 2029. This pass, which was once a major concern for astronomers due to the initial possibility of collision, could completely remodel the asteroid’s surface and cause a real “rain” of rocks. Scientists indicate that the interaction with Earth’s gravity could cause tremors and landslides on the asteroid itself, changing its configuration.
The investigation is led by Ronald-Louis Ballouz, a scientist at the Applied Physics Laboratory at Johns Hopkins University, in the United States. Ballouz explains that, over time, asteroids suffer “space weathering” through continuous bombardment by meteoroids, which wears down their surfaces. However, asteroids that pass close to planets, as is the case with Apophis, tend to exhibit reduced signs of this weathering, leading scientists to believe that planetary gravity can “refresh” their surfaces.
Discovered in 2004, Apophis is about 340 meters long and has a shape similar to a peanut, characteristics that, combined with its future proximity to Earth, made it an object of interest. Initial estimates indicated a possible collision, but more recent calculations in 2021 ruled out this hypothesis. The forecast is now that the asteroid will pass approximately 32 thousand kilometers from Earth – even closer than some of our orbital satellites. Although considered safe, this distance will allow scientists to closely observe the effects of the approach.
To test Apophis’ structural reactions, Ballouz and a team of researchers developed computational models based on the asteroid Itokawa, an asteroid with a similar structure that has been previously studied. In the tests, possible effects of the Earth’s gravitational attraction on Apophis were simulated, predicting two main changes: seismic tremors and changes in the asteroid’s rotation.
The seismic tremors, expected to begin about an hour before closest approach, could generate rockslides and dust on Apophis’ surface. However, given that the gravity on the asteroid is much weaker than on Earth – around 250,000 times less intense – scientists believe that some of the particles could be momentarily launched into space before settling back down. This movement could generate noticeable and changeable patterns, capable of being observed from instruments in Earth orbit.
Another possible effect is a change in Apophis’ rotation, called “tipping”. Instead of a regular rotation, the asteroid could adopt an unstable and irregular rotation, similar to the movement of a poorly thrown ball.
Ballouz’s team hopes to validate these predictions with help from NASA’s OSIRIS-APEX mission, which will be observing Apophis during its passage. This ambitious project will study the chemical composition of the asteroid and document any changes to the surface for 18 months, providing real-time data that may or may not prove the scientific predictions made so far.
This encounter offers a rare opportunity to understand the behavior of celestial bodies in passages close to planets and could also help clarify the impact of gravitational interactions of this type on the evolution of asteroids – valuable knowledge not only for science, but also for our preparedness facing potential space threats in the future.
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