What would happen if an asteroid hit Earth? Hollywood has used this scenario as a dramatic springboard more than once, but the threat of an asteroid colliding with Earth isn't just sci-fi fantasy. In 2013, an asteroid ruptured over Russia and injured more than 1,000 people; furthermore, many experts believe it was an asteroid collision that wiped out the dinosaurs. Before you start packing a bunker and preparing for the end, however, keep in mind the likelihood of an asteroid impact is minimal; NASA believes it's unlikely it will happen in the next 100 years. However, scientists, astronomers, and the US government have realized they should probably start preparing and planning just in case.
In 2018, the White House issued the National Near-Earth Object Preparedness Strategy and Action Plan to examine what would happen if an asteroid hit - and what we should do about it. The report outlines what actions the government needs to take to prevent such a catastrophe and how it will work with FEMA to respond to such a collision. Working with NASA and other space study programs all over the world is critical; the more eyes we have observing, tracking, and predicting, the better the response plans will be. Combining available technology, global databases, and running scenarios will help form a global defense.
Movie heroes can answer a catastrophic scenario with a happy ending, but asteroid impacts in the real world aren't guaranteed such a positive outcome. At least, not without the right preparations. Luckily, NASA and its international cohorts are on the job.
Up until the Trump administration ended it in 2017, NASA's Asteroid Redirect Mission (ARM) examined ways to possibly direct an asteroid to enter the moon's orbit rather than head toward Earth. In the White House's 2018 report, however, leaders cited their goals to create new technologies that could deflect asteroids and specifically mentioned kinetic impactors, a method which would bump an asteroid off course by hitting it with a strong force.
Through the Double Asteroid Redirection Test (DART), scientists plan to build a spacecraft they could launch at an incoming asteroid with enough force to knock it off-course without breaking it into potentially dangerous smaller pieces. Scientists plan on testing DART in 2021 by launching it at a small moon orbiting an asteroid called Didymos, selected because the moonlet is about the size of an asteroid that could potentially devastate Earth. Powered by solar panels, it will take more than a year for the spacecraft to reach the moonlet, traveling at speeds of up to 15,000 miles per hour.
While asteroid deflection methods could potentially redirect an asteroid's path, nuclear devices could theoretically be used if the danger isn't detected in enough time or the asteroid is too big. Scientists developed a model that would work to blow asteroids up if they are discovered to be within a year of a projected collision with Earth.
Scientist Bong Wie developed the Hypervelocity Asteroid Intercept Vehicle (HAIV), which would create a crater on an asteroid using kinetic impact and then fire a nuclear device into the hole. According to Wie, detonating the device inside the asteroid would be more effective, but he admits the detonation would send fragments of the asteroid down to Earth, causing damage or even taking lives.
Russian scientists examining similar applications of nuclear devices found that a 650-foot-wide asteroid would likely require a 3-megaton nuclear device in order to be taken out - hundreds of times more powerful than what decimated Hiroshima and Nagasaki.
The 2018 White House report includes gravity tractors as a possible solution to deflect asteroids headed toward Earth, and scientists are busy coming up with solutions that use this method. NASA has an "asteroid tractor" in the works and plans to use a 20-ton spacecraft to pull an asteroid into another orbit. According to Edward Lu and Stanley Love, who presented the concept, the spacecraft would hover above the asteroid and maintain a constant distance without touching it. Moving slowly, the craft would be able to tow the asteroid in another direction due to the gravitational attraction between the two.
The craft would be unmanned, meaning no astronauts have to be put in danger during the mission. However, the process would take years and would only work on asteroids fewer than 500 meters in diameter. It would also require scientists to discover potentially dangerous asteroids decades in advance, something Lu claims NASA is capable of doing.
The 2018 report calls for NASA to "identify opportunities in existing and planned telescope programs to improve detection and tracking by enhancing the volume and quality of current data streams," meaning leaders must recognize the importance of observatories and telescopes in keeping Earth safe. This includes several NASA-funded observatories both on the ground and in the sky. The Catalina Sky Survey at the University of Arizona operates telescopes that search for new asteroids and comets, including those that may be dangerous to Earth. The observatory's team found 65% of the 586 asteroids that came near Earth in 2011.
NASA and the Air Force both support the Pan-STARRS PS1 telescope in Hawaii that once discovered 19 near-Earth asteroids in a single night. Short for Panoramic Survey Telescope and Rapid Response System, the telescope uses a 1,400-megapixel camera to take more than 500 photos each night. It was specifically designed by scientists to search for asteroids.
Orbiting above the earth, the NEOWISE telescope has the ability to find more asteroids than the observatories on Earth, and robotic spacecraft like OSIRIS-REx can get close enough to asteroids to explore and even land on them.