NASA’s new 2016 budget includes money for two asteroid missions. One of those missions continues an effort underway for years, the detection of near-Earth objects (NEOs), asteroids that pose a risk of colliding with our home planet. The other mission proposes to land on a near-earth asteroid, pick up a large boulder from its surface, and redirect the boulder into an orbit around the Moon. Once in a stable lunar orbit, manned missions would visit the asteroid fragment and retrieve pieces to return to Earth for detailed study.
Both missions complement each other and serve multiple roles. The detection mission will help protect Earth from a potentially cataclysmic collision with an asteroid. It’s happened many times in the past, and it continues to happen now. The biggest recent impact came in 2013 over Chelyabinsk, Russia, from an asteroid estimated at a mere 18 meters in diameter.
The detection mission would also help NASA find a nearby asteroid from which it might pluck a piece. That mission to “redirect” a piece of an asteroid into orbit around the Moon would build our understanding of what asteroids consist of and how they might contribute valuable minerals for industry. Perhaps even more important, the “redirect” mission involves landing on an asteroid and moving a piece of it onto a different trajectory, skills we would need if we ever detected an asteroid on a collision course with Earth and wanted to deflect it away.
How many asteroids are out there? How big are they? How many are on a course that might bring them into contact with Earth one day? What are they made of and does their composition mean we might benefit by capturing one and mining it? Could we deflect an asteroid on a collision course with Earth? What spacecraft missions have already studied asteroids, and what have we learned?