[thedoc (OP)]

Tim asked the Naked Scientists:
   If a magnet was formed in space what would happen to its polarity if it fell to earth?
What do you think?

[Janus]

If the magnet is heated enough by its passage through the atmosphere, it will lose its magnetism completely as the domains randomize. Once it cools back down, the domains can realign with the Earth's magnetic field.  If it doesn't get hot enough to lose its magnetism it will retain its present polarity.