Planetary securityHow to Deflect an Asteroid
MIT researchers have devised a framework for deciding which type of mission would be most successful in deflecting an incoming asteroid. Their decision method takes into account an asteroid’s mass and momentum, its proximity to a gravitational keyhole, and the amount of warning time that scientists have of an impending collision — all of which have degrees of uncertainty, which the researchers also factor in to identify the most successful mission for a given asteroid.
On April 13, 2029, an icy chunk of space rock, wider than the Eiffel Tower is tall, will streak by Earth at 30 kilometers per second, grazing the planet’s sphere of geostationary satellites. It will be the closest approach by one of the largest asteroids crossing Earth’s orbit in the next decade.
Observations of the asteroid, known as 99942 Apophis, for the Egyptian god of chaos, once suggested that its 2029 flyby would take it through a gravitational keyhole — a location in Earth’s gravity field that would tug the asteroid’s trajectory such that on its next flyby, in the year 2036, it would likely make a devastating impact.
Thankfully, more recent observations have confirmed that the asteroid will sling by Earth without incident in both 2029 and 2036. Nevertheless, most scientists believe it is never too early to consider strategies for deflecting an asteroid if one were ever on a crash course with our home planet.
Now MIT researchers have devised a framework for deciding which type of mission would be most successful in deflecting an incoming asteroid. Their decision method takes into account an asteroid’s mass and momentum, its proximity to a gravitational keyhole, and the amount of warning time that scientists have of an impending collision — all of which have degrees of uncertainty, which the researchers also factor in to identify the most successful mission for a given asteroid.
The researchers applied their method to Apophis, and Bennu, another near-Earth asteroid which is the target of OSIRIS-REx, an operational NASA mission that plans to return a sample of Bennu’s surface material to Earth in 2023. REXIS, an instrument designed and built by students at MIT, is also part of this mission and its task is to characterize the abundance of chemical elements at the surface.
In a paper appearing this month in the journal Acta Astronautica, the researchers use their decision map to lay out the type of mission that would likely have the most success in deflecting Apophis and Bennu, in various scenarios in which the asteroids may be headed toward a gravitational keyhole. They say the method could be used to design the optimal mission configuration and campaign to deflect a potentially hazardous near-Earth asteroid.
