By using gravity as your tow line, you can sidle up to an asteroid. Maintain it for a year and that should give it enough nudge to miss the earth 20 years later. |
Impacts and explosions are difficult to predict and control. When you're trying to save the Earth, you want them to be both controllable and predictable. |
It's like changing the angle of a bank shot in pool. A little change early on has a large effect down the line. |
This saves you from having to land on the asteroid and then trying to stabilize yourself on a flying pile of rock and debris which is spinning all the time. |
We know enough about this asteroid to know it is a potential threat but we still have a few more years to watch this thing and get a better handle on what it is going to do. |
You just want to hang there and let the spacecraft gradually adjust the asteroid's course. |