Asteroid Apophis: Reassessing the Risks of a Close Encounter with Earth
Asteroid Apophis, a space rock that could have a chance of colliding with Earth. While the overall risk remains reassuringly low, one notable omission from our list was the near-Earth asteroid 99942 Apophis.
When first discovered in 2004, Apophis caused alarm among astronomers by initially ranking as the most hazardous known asteroid, with a 2.7% chance of impacting Earth in 2029. Further projections suggested a potential second encounter in 2036. However, subsequent detailed observations and refined calculations effectively ruled out the possibility of an impact, reducing the estimated risk to nearly zero.
A New Perspective on Apophis’ Trajectory
Despite these reassuring calculations, a recent study led by a Canadian research team has introduced a slightly different perspective. Their findings suggest that the probability of an impact in 2029 or 2036, while still very low, might be marginally higher than previously thought.
Based on current orbital predictions, Apophis will make close approaches to Earth in 2029, 2036, and again in 2068. While it remains unlikely that the asteroid itself will collide with our planet, researchers have considered a different, though improbable, scenario: a secondary collision. If Apophis were to strike another space object during its journey—such as an asteroid or a fragment of space debris—it could alter its course, potentially directing it towards Earth.
How a Collision Could Alter Apophis’ Path
A study conducted by astronomers from the University of Western Ontario aimed to quantify the likelihood of such an event and to determine the size of an object required to deflect Apophis into a hazardous trajectory. According to their findings, a collision with an object as small as 60 cm in diameter could alter Apophis’ orbit slightly. However, an impact with an object measuring approximately 3.4 meters across could generate a significant enough deviation to create a real risk of Earth impact.
Given that Apophis itself has an elongated, egg-like shape with a diameter of approximately 370 meters, the direction of any potential collision is also a critical factor. Line Drube, an astrophysicist and asteroid researcher at DTU Space in Denmark, explains, “The object must not only strike Apophis, it must also push the asteroid in the right direction to cause a collision with Earth.”
How Likely is a Secondary Collision?
While the possibility of two space objects colliding is not unheard of, it remains extraordinarily rare. Recorded instances of asteroid or comet collisions have been inferred from long-term monitoring, but the odds remain minuscule. The Canadian study estimates that the chance of a space object large enough striking Apophis before its 2029 flyby is less than one in two billion.
For an impact at any later point in time, such as before the 2036 or 2068 close approaches, the probability is calculated at less than one in a million. These figures, while slightly higher than earlier estimates, remain reassuringly low.
A Rare Opportunity for Scientific Discovery
Rather than being a cause for alarm, Apophis’ close pass in 2029 is viewed by many scientists as an extraordinary research opportunity. Drube remains unworried, stating, “Apophis comes super-close to Earth, but the probability of it hitting us is so low that it does not worry me at all.”
Instead, researchers are eager to observe the effects of Earth’s gravitational pull on the asteroid. As Apophis travels past, tidal forces will stretch and compress its structure, potentially revealing crucial insights into its composition and density. This knowledge could inform future planetary defense strategies, helping scientists devise better ways to deflect potential threats—or even explore alternative approaches, such as capturing and mining asteroids for valuable resources.
The 2029 flyby of Apophis is an exceptionally rare event. Experts estimate that an asteroid of this size comes this close to Earth only once every 5,000 to 10,000 years. As we prepare to witness this remarkable astronomical occurrence, one thing remains clear: Apophis is an asteroid worth watching, not fearing.
