Earth’s gravity could shake the ‘chaos god’ asteroid in 2029

In a close encounter that could change its very structure, the asteroid Apophis is expected to experience dramatic surface changes when it passes Earth on April 13, 2029.

This brief interaction with our planet’s gravity could cause tremors and landslides on Apophis, potentially transforming its surface, according to a new study.

Ronald-Louis Ballouz, an asteroid scientist at the Johns Hopkins University Applied Physics Laboratory, explained that asteroids like Apophis undergo constant “cosmic weathering” as a result of being bombarded by tiny meteoroids that gradually change their surface.

However, asteroids passing close to planets often weather less than asteroids further out in space, leading to the theory that planetary gravity may be responsible for resurfacing such space rocks.

About Apophis

Apophis, a 1,100-foot (340-meter) long asteroid named after the Egyptian god of chaos, was discovered in 2004. The peanut-shaped asteroid quickly gained attention due to its size and its initial predicted close pass of Earth.

Preliminary estimates suggested a higher probability of impact, but by 2021, astronomers had refined their calculations and determined that Apophis, although close, would not collide with Earth. Instead, the asteroid is expected to pass within 20,000 miles (32,000 kilometers) of Earth, closer than many of our orbiting satellites.

Although this distance is considered safe for Earth, scientists are wondering how this close passage might affect Apophis itself.

To explore this idea, Balluz and an international team of researchers developed computational models of Apophis using data from another widely studied two-lobe asteroid, Itokawa. Their simulations tested how Apophis might respond to Earth’s gravitational pull, simulating both large-scale and small-scale structural effects as 2029 approaches.

Earth’s Gravity and Apophis

Their results suggest that two main processes, both caused by Earth’s gravity, could significantly alter the surface of Apophis. The first is associated with seismic tremors, which are expected to begin about an hour before Apophis reaches closest approach and continue for some time after that.

While the intensity of these tremors remains uncertain, Ballouz explained that even minor seismic events on Earth are likely to have a noticeable impact on Apophis because of its gravity about 250,000 times weaker than Earth’s. Tremors can shake boulders and rocks, causing some to rise briefly into space before falling back, creating noticeable patterns that would be seen as a spacecraft flies past.

The second transformative process can affect the rotational dynamics or “tumbling” of the asteroid. Unlike stable uniaxial rotation, Apophis rotates chaotically, like a poorly thrown soccer ball.

A separate study published in 2023 found that Earth’s gravity would change the rate at which Apophis falls, either speeding up or slowing it down depending on its orientation as it approaches Earth.

New modeling confirms this and further shows that such changes could destabilize the rock slopes on its surface. Over time, this gradual destabilization may even trigger landslides.

Future plans

To better understand these changes, Ballouz and his team hope to collect real-time data from NASA’s OSIRIS-APEX mission. This spacecraft is repurposed from the OSIRIS-REx mission, which collected samples from space. asteroid Bennuintends to observe Apophis during its transit in 2029.

Over the course of 18 months, OSIRIS-APEX will study Apophischemical composition and document surface changes, potentially confirming Ballouz’s hypotheses and providing new insight into the effects of planetary collisions on small bodies.

As Apophis approaches, the scientific community is poised for a rare observational opportunity. This close encounter could shed light not only on the processes that form asteroids, but also on the complex dynamics of space weathering and planetary interactions.

The study is currently available on the website arXiv preprint database.