Can We Deflect Asteroids on Trajectory with Earth?

NASA has just launched its probe OSIRIS-REx, which has been renamed the OSIRIS-APEX (Origins, Spectral Interpretation, Resource Identification, and Security – Apophis Explorer) to study the asteroid Apophis, which is expected to fly by Earth in five years. The asteroid, also referred to as the "God of Chaos," is projected to pass Earth on April 13, 2029, at an extremely close proximity of roughly 20,000 miles, nearer than some artificial satellites, and may be visible from the Eastern Hemisphere.

The spacecraft is set to rendezvous with the S-type asteroid, which is composed of silicate materials and nickel-iron, on April 13, 2029. Instead of landing, however, it will maintain close proximity to the asteroid for a duration of 18 months. During this time, the spacecraft will not only observe surface alterations but will also undertake tasks such as mapping the asteroid's surface and examining its chemical composition, as stated by NASA.

The mission includes a maneuver where the spacecraft will approach as close as 16 feet from the asteroid's surface. This proximity will allow it to fire its thrusters towards the surface, effectively stirring up material. This action will provide researchers with valuable insights into the subsurface composition of the asteroid.

Even though the asteroid's closest approach to Earth is still five years away, scientists are already preparing to observe it as the probe makes the first of its six near encounters with the sun.
Of course, an event like this always raises the obvious question, which is: what if a massive asteroid were to be headed straight for Earth? What would we do then? Do we have the means to deflect such a threat?

The short answer is that we do not yet know. Scientists have debated whether we are capable of exploding an asteroid before it reaches Earth or firing a projectile at it to “bounce” it away.

Either way, preventing an asteroid from crashing into Earth involves a range of strategies based on detection, analysis, and intervention. The first step is always early detection, using telescopes and radar to continuously scan the sky for near-Earth objects (NEOs). Early detection is crucial as it provides time to plan and execute a response.

Once a potentially hazardous asteroid is identified, scientists calculate its trajectory to determine the risk of impact. If an impact is predicted, various methods can be employed to alter the asteroid's path.
One common idea is the kinetic impactor technique. This involves sending a spacecraft to collide with the asteroid at high speed, changing its velocity and trajectory just enough to miss Earth. The success of this method depends on the mass and speed of the spacecraft and the size and composition of the asteroid.

Another approach is the gravity tractor method. A spacecraft would fly alongside the asteroid for an extended period, using its gravitational pull to slowly alter the asteroid's path. This method is more precise than the kinetic impactor but requires more time to be effective.

Nuclear explosions are also considered as a last resort. Contrary to popular belief, the idea isn't to blow the asteroid apart, as this could create multiple hazardous fragments. Instead, a nuclear detonation would be conducted near the asteroid to superheat its surface, creating a powerful jet of vaporized material that acts like a rocket engine, pushing the asteroid off course.

Additionally, technologies like laser ablation, where lasers are used to vaporize material and create a thrust, and attaching a solar sail to the asteroid to use solar radiation pressure for course alteration are theoretical options still in development.

Coordination on a global scale is vital in these efforts. International space agencies and governments would need to collaborate to track NEOs and deploy any chosen intervention method. Continuous research and development in asteroid deflection technologies are essential to improve our capabilities to protect Earth from potential asteroid impacts.

In the meantime, hopefully, we will get to enjoy seeing the God of Chaos fly safely by in five years’ time.