All you need is a letter of the alphabet to solve today's mentalfloss.com Think Thursday Brain Game. Fill in the question mark with the correct letter - and good luck:

M, ?, E, M, J, S, U, N

Here is the ANSWER. 

THE ANSWER:

V.

The planets in our Solar System are, from the Sun outward:
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.

Thanks for playing! Tomorrow, it's Free-for-All Friday!