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.

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

ANSWER:  MERCURY.

Thanks for playing, and have a great weekend!