The likelihood of an asteroid hitting Earth in the next hundred years is a topic of much debate among scientists. While it is difficult to predict with certainty as to when and where an asteroid will hit, there is one particularly fearsome asteroid which has had the scientists go jittery.

Near-Earth Objects

One important factor to consider is the number of known asteroids that are on a collision course with Earth. According to NASA's Center for Near-Earth Object Studies (CNEOS), there are currently 1,913 known asteroids that have been classified as "potentially hazardous" due to their proximity to Earth and their size. Of these, approximately 20% are considered to have a significant likelihood of hitting Earth in the next hundred years.

Another important factor to consider is the rate at which asteroids are discovered. According to CNEOS, the number of known asteroids has been increasing at a steady rate over the past few decades, with the majority of discoveries being made by automated sky surveys. This suggests that the likelihood of an asteroid hitting Earth in the next hundred years may be higher than previously thought, as more asteroids are being detected.

The most formidable example of an asteroid that has a significant likelihood of hitting Earth in the next hundred years is asteroid Apophis. 

Chaos incarnate

Named after the Egyptian deity that is “chaos incarnate”, the asteroid, which is estimated to be around 1,000 feet in diameter, was first discovered in 2004 and is considered to be a "potentially hazardous asteroid." According to CNEOS, Apophis has a 1 in 150,000 chance of hitting Earth in the year 2068.

First discovered in 2004 by astronomers at the Kitt Peak National Observatory in Arizona, the asteroid has a diameter of approximately 340 metres, making it one of the largest near-Earth asteroids that has been discovered to date.

Apophis has a very unusual orbit that brings it incredibly close to the Earth, with a minimum distance of just 31,300 kilometres (19,460 miles) during its next flyby in 2029. This is roughly a tenth of the distance between the Earth and the Moon, and it is close enough to be visible to the naked eye.

The terrifying catch

During this close encounter, Apophis will pass through a gravitational keyhole, which is a small region of space that, if the asteroid were to pass through it, would set up a future impact with Earth exactly seven years later on April 13, 2036. The keyhole is estimated to be no more than about 100 metres in diameter, which is a very small region of space considering the asteroid's size and the distance it will be from Earth during the close encounter.

The gravitational keyhole is created by the gravitational pull of the Earth and the Moon. The gravitational pull of the Earth and the Moon can cause small changes in the asteroid's orbit, which can lead to a future impact with Earth. The gravitational keyhole is a sensitive region of space, and even small changes in the asteroid's trajectory can cause it to pass through it and set up a future impact.

The probability of Apophis passing through the keyhole during its 2029 close encounter is estimated to be about 1 in 250,000. While this may seem like a low probability, it is still considered to be a significant risk, and scientists and engineers are closely monitoring the asteroid's trajectory to ensure that it does not pass through the keyhole.

The asteroid's orbit also makes it a potential Earth impacter in the future, with a small chance of impact in the year 2068. However, scientists have determined that the probability of an impact is extremely low, estimated at about 1 in 150,000.

The consequences of a collision

If Apophis were to impact the Earth, it would be a catastrophic event. The asteroid is estimated to be around 1,100 feet in diameter and weighs approximately 27 billion pounds. The impact would release energy equivalent to billions of atomic bombs, causing widespread destruction and devastation. The immediate effects would include a massive fireball and a shockwave that would level buildings, forests, and other structures within a radius of several miles. 

The asteroid would also create a massive crater, potentially hundreds of feet deep and several miles wide. The destruction would not be limited to the immediate impact area, as debris would be thrown into the atmosphere, blocking out sunlight and causing global cooling. 

The long-term effects would be even more devastating, with widespread famine, disease, and mass extinction of plant and animal life. The impact would likely cause a mass extinction event, similar to the one that wiped out the dinosaurs.

The scientific potential

Apophis has sparked interest and concern in the scientific community for its potential to collide with our planet. However, this proximity also opens up new opportunities for future space exploration. Scientists and researchers have been studying Apophis, and have outlined potential plans to mine the asteroid for valuable resources such as precious metals and water.

Apophis could also serve as a valuable target for future space missions. The asteroid's proximity to Earth makes it an accessible destination for spacecraft, and studying Apophis could provide valuable insights into the origins of our solar system and the potential for other celestial bodies to collide with Earth.

Additionally, missions to Apophis could serve as a test bed for new technologies and techniques in space exploration. Apophis's next near-Earth encounter in 2029 will be a valuable opportunity for NASA's DART mission. It will allow scientists to test the feasibility of redirecting an asteroid's trajectory and to gather data that will be crucial for future missions to Apophis.

NASA’s DART Mission

NASA’s Double Asteroid Redirection Test (DART) is aimed at testing a method of planetary defense against near-Earth objects. It was designed to assess how much a spacecraft impact deflects an asteroid through its transfer of momentum when hitting the asteroid head-on.

DART is a spacecraft that will be sent to collide with an asteroid to test the feasibility of redirecting its trajectory. Apophis, with its size and proximity to Earth, is the perfect target for this mission.

The DART mission will aim to hit Apophis with a kinetic impacter, which is a spacecraft that uses its own speed and mass to change the asteroid's trajectory. The mission will be able to measure the effect of the collision on Apophis's velocity and trajectory, thus, helping scientists to better understand how to redirect an asteroid's path if it poses a threat to Earth.

In conclusion

Apophis's next near-Earth encounter in 2029 will occur when the asteroid is close enough to Earth to be observed by telescopes and radar, providing scientists with a unique opportunity to gather data on the asteroid's orbit, rotation, and physical properties. This data will be crucial in understanding the asteroid's behavior and in planning future missions to Apophis.

It is important to note that the probability of impact for these asteroids is continually being updated as new observations are made and new data is collected. NASA and other organisations are constantly monitoring these asteroids to ensure the safety of our planet.

Apophis is a fascinating asteroid that is of great interest to scientists due to its proximity to Earth and potential impact hazard. However, the risk of an impact is extremely low, and the asteroid also provides an opportunity for valuable scientific study.