Near-Earth asteroids are a serious risk for humanity as we still know little about these objects and their properties. Strategies and tabletop exercises have been employed over the last few years to make us more prepared, and researchers have now produced an interesting tool that could be used as well.
Soon to be reported in Acta Astronautica, engineers from the Massachusetts Institute of Technology (MIT) have created a decision map tool to help us decide what’s the best mission to employ when dealing with potentially risky asteroids. The idea particularly focuses on ensuring asteroids avoid gravitational keyholes, small regions of space where a planet’s gravity can turn a risky asteroid into a planet-killer.
“People have mostly considered strategies of last-minute deflection, when the asteroid has already passed through a keyhole and is heading toward a collision with Earth,” lead author Sung Wook Paek, a former graduate student in MIT’s Department of Aeronautics and Astronautics, said in a statement. “I’m interested in preventing keyhole passage well before Earth impact. It’s like a preemptive strike, with less mess.”
Acting in advance could be crucial and that’s where the framework kicks in. Missions to deflect an asteroid will have to deal with a lot of uncertainties regarding their target. The asteroid’s mass, composition, and momentum all need to be known if we are to shift its orbit away from Earth. But this might not be possible and the missions might have to be launched with significant unknowns, some of which could lead to failure and have deadly consequences.
“Does it matter if the probability of success of a mission is 99.9 percent or only 90 percent? When it comes to deflecting a potential planet-killer, you bet it does,” co-author Professor Oliver de Weck of MIT added. “Therefore we have to be smarter when we design missions as a function of the level of uncertainty. No one has looked at the problem this way before.”
The team considered three scenarios for potential missions. The first involves sending a kinetic impactor probe, a spacecraft that will crash into the asteroid to push it off its course. The second sends a scout mission to measure the asteroid followed by a kinetic impactor. The third has two scouts, one to measure the asteroid and one to push the asteroid slightly off course, followed by the major kinetic impactor.
The team plugged properties of real asteroids into their simulations, such as 99942 Apophis, which will fly very close to Earth in 2029 and then again in 2036. In their framework, they saw that if Apophis were going to pass near a gravitational keyhole in five years or so, there would be enough time to send the two scouts followed by the impactor. If this were to happen just two to five years in the future, the second scenario is preferable. Any sooner than that and things get very troubling. The kinetic impactor alone might not be enough to push the asteroid away.
The work is very interesting but assumes that we will be aware of asteroids well in advance and that we are ready to launch a mission at the drop of a hat. This might not be the case in real life.