Written by Yuvraj Dhillon
Without a necessary mechanism of early detection and neutralization in place, humanity is always at a risk of being bombarded by asteroids, comets, and other space objects which could cause cataclysmic destruction.
So you sit down on your sofa with your television on the play, popcorn hot, and Netflix ready to binge, when suddenly you hear shrilling screams and people outside the window all pointing up at the sky. You walk out through your door and notice something really gigantic heading towards earth - an asteroid. Can something like this really happen? Are we really doomed to die by a rock?
Not to worry. NASA and other space agencies won’t let that happen. NASA has a well established Planetary Defense Coordination Office (PDCO) in place to protect the earth from such asteroids. There is constant monitoring of possible threats to the earth, both far and near. For the objects that are nearer to the earth, there is a functioning program in place known as the "Near Earth Observation Program".
Near-Earth Observations Program
The key element of NASA’s planetary defense effort is the Near-Earth Object (NEO) program, which comprises of projects that locate, track, and characterize 90 percent of the predicted number of NEOs that are 140 meters and larger in size–larger than a small football stadium–and to characterize a subset representative of the entire population.
Objects of this size and larger pose a risk to Earth of greatest concern due to the level of devastation its impact would cause and should continue to be the focus of global search efforts. While no known asteroid larger than 140 meters in size has a significant chance to hit Earth for the next 100 years, it's still better to be safe than sorry.
The NEO Observations Program sponsors projects that make use of telescopes around the world to search for NEOs, track them across the sky to determine their orbits, and gain information on their sizes, shapes, and composition.
Okay, so we have the technology we need to detect Near Earth Objects, but what if there is, in fact, an asteroid or comet that decides to head toward the earth? Houston, we have a plan.
Enter DART Mission
The DART(Double Asteroid Redirection Test) Mission is one directed by NASA with the objective of preventing possible hazardous impacts of asteroids with our planet. The goal is really simple - to change the course of an asteroid before it even reaches the earth’s atmosphere, by colliding a spacecraft named DART into the targeted asteroid. The impact could successfully deflect the asteroid on a collision course with earth.
The first-ever demonstration of this technology is planned to take place using a launch on a Falcon 9 rocket on July 22, 2021, planning to intercept Didymos(an asteroid almost a kilometer in diameter!), which has been classified as a potentially hazardous asteroid and near-earth object.
As has been estimated, the impact of the 500 kg DART spacecraft crashing the asteroid Didymos at a blazing 6.6 km/s will produce a velocity change of 0.4 mm/s. It looks pretty small, but over time, it actually leads to a significant change in trajectory. Significant enough to get it far away from our beautiful planet.
Provided the mission is successful, further iterations of this technology could be used to successfully deflect asteroids even closer to earth using better propulsion technology, because of more momentum in striking the asteroid/comet results in further change in its trajectory.
Or well, if nothing else works, there are always nuclear missiles to get the result we need, although they are super expensive(cost in billions of $) and their use is politically controversial( *ahem ahem* North Korea).