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But first, they have to get the lander on the ground, and that's where the worry comes in. In fact, they have a name for it in the Mars exploration community: "seven minutes of terror."

Can I replace where with when?

Thanks!
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That's the worrying bit/part
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>Can I replace where with when?
Not really
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Sorry I misread your question!!!
You could say - and that's the worrying part.
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