The asteroid-capture mission remains in a "preformulation" phase at the moment, as NASA is still gathering data and sorting through ideas. The space agency hopes to have a basic mission concept in place by around the end of the year, officials have said.
In addition to the gravity tractor method, incoming space rocks could also be knocked off course with a direct hit by a "kinetic impactor," researchers say. (These techniques could also be combined in two coordinated space missions, slamming an asteroid with an impactor probe and then sending a gravity tractor out to finish the job.)
More extreme measures might be necessary for extremely large asteroids and space rocks detected with little warning time. In such cases, a nuclear bomb might be humanity's best - and perhaps only - option.
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