Diverting Asteroids

The DART mission (Double Asteroid Redirection Test) determined that new planetary spacecraft technologies have the capacity to deflect Earth-bound asteroids.

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By Jason Lei

There have been numerous theories about the cause of the extinction of the dinosaurs, from great volcanic activity to climate change caused by retreating sea levels. However, most agree that the impact of a large asteroid played a major role in dinosaur extinction. About 66 million years ago, the six-mile-wide Chicxulub asteroid collided with Earth, leading to dense clouds of dust blocking the Sun’s rays, darkening and cooling the planet to deadly environmental conditions for most living organisms, including the dinosaurs.

Asteroids are rocky celestial objects remaining from the birth of our solar system that orbit the Sun. The solar system was formed about 4.6 billion years ago when a giant cloud of gas and dust collapsed. Most of the material fell to the center of the cloud and created the Sun, while the giant disk of dust surrounding the Sun formed the planets. However, the objects in the asteroid belt, a region of space between the orbits of Mars and Jupiter, never had the chance to become planets. These space rocks of all different sizes, known as asteroids, began to orbit in the same path as the planets around the Sun. Most asteroids are harmless to Earth, since compared to the solar system, Earth is merely a speck of dust, and asteroids are even more minor than that. Instead of moving randomly, asteroids are also on elliptical orbits; in fact, their chance of colliding with Earth in our lifetime is 1 in 10,000

Though asteroids have a low probability of ever hitting Earth, many NEOs (near-Earth objects) and PHOs (potentially harmful objects) have been reported. For example, the asteroid QQ47 was found in 2003 and gained media attention since it reportedly had a very small possibility of striking Earth in 2014. On the Torino Impact Hazard Scale, which ranges from 0 to 10, the asteroid QQ47 was rated a 1. Impact events at the Torino Scale 1 certainly warrant careful monitoring by astronomers, but only a few asteroids have briefly reached the Torino Scale 1 since then. In all cases, more accurate predictions made after careful observation of the asteroids' positioning later allowed scientists to rule out any possibility of an Earth impact. Another famous example of a false prediction includes the 1,100-foot-wide asteroid 99942 Apophis, discovered in 2004, which had the highest probability of colliding with Earth. It was predicted that it would become dangerously close to Earth in 2068. However, NASA ruled out this impact in 2021, when a radar observation, combined with precise orbit analysis, allowed astronomers to conclude that there is no risk of Apophis impacting our planet for at least a century; it will harmlessly pass the planet in 2068. 

It is undeniable that reports of potential asteroid impacts have caused media frenzy and public panic throughout history. NASA’s DART mission aims to answer some of humanity’s biggest questions about the dangers of asteroid impacts.

The DART (Double Asteroid Redirection Test) mission was a demonstration to determine if kinetic impactor technology, which involves artificially impacting an asteroid to adjust its speed and path, could be used for asteroid deflection. It was launched November 23, 2021 with the help of a DART spacecraft designed to impact an asteroid and test its technology. DART’s target was the binary asteroid system Didymos. Didymos was the ideal candidate for the experiment, as it poses no actual threat to Earth since it is not on a collision path. The system was composed of two asteroids: the larger Didymos asteroid and a smaller moonlet asteroid, Dimorphos, which orbited the larger one. In September 2022, the timing of the DART impact was chosen specifically so that the distance between Earth and Didymos was minimized to enable the highest quality telescopic observations. The spacecraft successfully collided with Dimorphos nearly head-on, shortening the time it took for the small asteroid moonlet to orbit Didymos. Prior to the DART mission, the orbital period of Dimorphos around Didymos was 11 hours and 55 minutes; NASA considered 73 seconds or more to be the minimum successful orbit period change of Dimorphos. The data shown by the DART surpassed this minimum benchmark by more than 25 times with the orbital period reduced by 33 minutes!

The success of the DART mission is one big step forward in the fields of Earth and space science. The deflection of the smaller asteroid’s orbit provides hope that NASA could deflect an Earth-bound asteroid if necessary. DART was more than just a test impactor for asteroids; it provides a means of halting the media's drastic claims and quelling public fear by indicating that altering an asteroid’s path is possible. DART is revolutionary because it uses brand-new technologies to enhance spacecraft function and communications. It used cutting-edge technology never previously flown on a planetary spacecraft to give humans the ability to potentially prevent a similar occurrence as the asteroid that devastated the dinosaurs.