Every time we detect an asteroid from outside the Solar System, we should immediately launch a mission to fling one of our asteroids back in the direction it came from.

"Interstellar Asteroid", by Randall Munroe, licensed under Creative Commons Attribution-NonCommercial 2.5 License

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Every time we detect an asteroid from outside the Solar System, we should immediately launch a mission to fling one of our asteroids back in the direction it came from.