NASA’s Apophis Asteroid Flyby Just Got More Complicated — And Scientists Explain Why

The approaching flyby of asteroid Apophis is attracting renewed attention from astronomers as scientists prepare for one of the most remarkable close encounters between a large asteroid and Earth in modern history. Scheduled for April 13, 2029, the encounter will bring Apophis extraordinarily close to our planet, offering researchers a rare opportunity to study how Earth’s gravity affects a passing asteroid.

Apophis is estimated to measure approximately 340 meters (1,100 feet) across. When it passes Earth in 2029, it is expected to come within roughly 32,000 kilometers (20,000 miles) of the planet’s surface. That is closer than the orbits of many geostationary satellites, making the event especially significant for planetary scientists. Despite the dramatic distance, NASA has confirmed that Apophis poses no impact threat to Earth during this encounter.

What makes the flyby scientifically complicated is not a predicted collision, but the number of physical processes researchers want to understand. As Apophis passes through Earth’s gravitational field, our planet’s gravity will alter the asteroid’s trajectory and may affect its rotation. Scientists are also investigating how tidal forces could influence the asteroid’s surface, structure, and internal arrangement.

One major concern is that Apophis may not behave like a solid, unchanging rock. Its surface could experience landslides, shifting material, or small asteroid-wide tremors as Earth’s gravity pulls on it. These changes could reveal whether Apophis is a compact rocky body or a loosely assembled collection of rocks and debris. NASA’s OSIRIS-APEX mission is designed to investigate precisely these questions after the encounter.

There is another complication that researchers are examining: the crowded environment around Earth. A recent scientific study explored the possibility of Apophis interacting with objects in high Earth orbit, including abandoned space debris. The probability of a collision is considered extremely low, but even a small impact could potentially affect the asteroid’s rotation or complicate planned observations and experiments. This is a research concern, not a prediction that such a collision will happen.

NASA’s OSIRIS-APEX spacecraft will play a central role in understanding what happens. Originally known as OSIRIS-REx, the spacecraft successfully delivered samples from asteroid Bennu in 2023 before beginning its extended journey toward Apophis. It is expected to arrive shortly after the asteroid’s closest approach in April 2029 and spend approximately 18 months studying its surface, composition, and physical changes. Scientists hope to compare observations taken before and after the flyby to identify the effects of Earth’s gravitational influence.

The encounter is also important for planetary defense. Understanding how an asteroid responds to gravitational forces, how its surface material moves, and how accurately its orbit can be predicted could improve future models used to assess potentially hazardous space objects.

For now, the most important fact remains reassuring: NASA’s calculations show that Apophis will safely pass Earth, with no known impact threat for at least the next 100 years. The real challenge is scientific. Researchers must prepare to observe a rare event in which an asteroid comes close enough for Earth’s gravity to visibly influence its physical behavior.

When Apophis passes Earth in 2029, it may become one of the most closely watched asteroids in history. Could this extraordinary encounter reveal how these ancient space rocks are held together—and help humanity better prepare for future asteroid threats?

What interests you most about the Apophis flyby: the possibility of asteroid tremors and surface changes, or the chance to watch such a large asteroid pass closer than many satellites?