Placing an asteroid in lunar orbit seems like a bad idea

1. sending a robotic ship out to an asteroid heading in our direction,
2. harvesting a boulder from the asteroid’s surface,
3. using the boulder as part of an “Enhanced Gravity Tractor” to deflect the asteroid’s path, and
4. the robotic ship returning with the boulder to a stable lunar orbit for further study.

This is how NASA explains ARM:

NASA is developing a first-ever robotic mission to visit a large near-Earth asteroid, collect a multi-ton boulder from its surface, and redirect it into a stable orbit around the moon. Once it’s there, astronauts will explore it and return with samples in the 2020s. This Asteroid Redirect Mission (ARM) is part of NASA’s plan to advance the new technologies and spaceflight experience needed for a human mission to the Martian system in the 2030s.

NASA has identified multiple candidate asteroids and continues the search for one that could be redirected to near the moon in the 2020s. Since the announcement of the Asteroid Initiative in 2013, NASA’s Near-Earth Object Observation Program has catalogued more than 1,000 new near-Earth asteroids discovered by various search teams. Of those identified so far, four could be good candidates for ARM. Scientists anticipate many more will be discovered over the next few years, and NASA will study their velocity, orbit, size and spin before deciding on the target asteroid for the ARM mission.

The Asteroid Redirect Mission is one part of NASA’s Asteroid Initiative. The initiative also includes an Asteroid Grand Challenge, designed to accelerate NASA’s efforts to locate potentially hazardous asteroids through non-traditional collaborations and partnerships. The challenge could also help identify viable candidates for ARM.

Here is a dramatic video demonstrating how this could work:

Here is a variation of this plan designed to capture asteroids that are moving freely through space:

It may just be me but bringing a boulder into lunar orbit seems like it could be a bad idea if something goes wrong. I can see a sci-fi movie being made about a catastrophe on Earth when a well-meaning mission like this results in a big rock flying into the planet and wiping out half of North America.

It might even star Bruce Willis …

Image credit: NASA