Exploding versus Diverting Asteroids Aimed at Earth
Date: Summer 2013
It has been said that if an asteroid was heading towards Earth, we would not want to send up explosives, since 'we would go from one dangerous object to many'. But would it also be true that smaller things coming into our atmosphere would all burn up to a greater degree than the big thing, if not entirely? The many small things would have much more surface area exposed to the atmosphere. Some percentage of the small objects might end up missing Earth entirely, as well, reducing the overall damage.
Turning one 2-mile asteroid into 2 pieces that are 1 mile each would not be a 'win' for the planet, of course - but it seems that turning it into a lot of pieces the sizes of basketballs or cars would at least take things from catastrophic to just problematic.
Good question. Actually you, and the film Deep Impact, got it right. Blowing up an asteroid into squillions of little pieces would be fine, but breaking it apart into a few pieces would not. The best solution is still to divert it in advance.
David H. Levy
I would tend to agree with your analysis, but I offer some additional considerations:
Success is never guaranteed. Problems at launch, e.g. a catastrophic explosion with loss of mission and or collateral human injury is always a possibility. These missions also involve great financial expense, so the loss would also be measured in dollars. Other problems could include missing the target, or perhaps steering the object in a direction that could unintentionally threaten MORE heavily populated areas. One could argue in this case that "better left alone" was a wiser approach. Hostilities could erupt if unintentional misdirection of the object led to great damage and loss of life in the affected region. This might be hard to substantiate, but some countries could depart from logic and presume the targeting was intentional.
Additionally, if you research the decisions that went into how rocket/people launches would occur, you can see there is not always uniform opinion on how to proceed with a particular mission. At NASA, for example, there were ideas in missions to launch people and fuel separately and then have a post-launch docking of the fuel craft with the one carrying the humans. The system of launching humans and fuel together seems the obvious better way to proceed, but this was not a quick, easily-made decision. Arriving at a decision on how to launch a mission to destroy or alter the course of an approaching object might be a difficult task. Obviously, as you infer, impending doom could help move the arguments toward a sensible timely resolution.
Your question is a good one and deserves consideration.
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Update: December 2011