Earlier this week we were blown away by those amazing images of the North Island, shot from the International Space Station. 

A few days later we've been wondering if a giant lump of Russian space junk was going to smash into the South Island. 

It hasn't, but it is going to come down somewhere - and it illustrates the extreme nature of space exploration. 

Astronomer and space scientist Dr Duncan Steel joined Tim Dower. 

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