There is not really an answer for what to do at that time, since all life has been destroyed, and earths gravitational field has probably been greatly lessened, due to the drop in mass. When it really gets down to it, you probably only have rations for a month, and unless you can start farming on the moon, you are going to have lots of fun with that starvation. So I would probably take the cowards way out, though I hate to say it.
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