Correct!
Mercury is the closest planet to the sun, making it the first planet in our solar system.
If you would like to learn more about Mercury click on the following links.

	http://www.kidsastronomy.com/mercury.htm
	http://kids.nineplanets.org/mercury.htm
	http://solarsystem.nasa.gov/planets/profile.cfm?Display=Kids&Object=Mercury

Next question: What planet is sometimes considered the sister planet to Earth?

Mars

Venus

Comet