Brain Game: 540 Months and Counting

Today's my birthday, so I'm turning the tables by giving you a gift: an easier-than-most mentalfloss.com Brain Game Free-for-all Friday challenge. Good luck!

Thirty-nine years ago today, the Mariner 10 became
the first spacecraft to visit which planet in our Solar System?

Here is the ANSWER.

March 29, 2013 - 9:33am
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