...and took the first close up images of its surface.

The quality and quantity (22 in all, but the last few were unusable) left something to be desired, plus they were beamed back to Earth at 8 bits per second, but they were the first such images from a world other than the Moon:

http://nssdc.gsfc.nasa.gov/imgcat/html/mission_page/MR_Mariner_4_page1.html

The many craters, lack of visible canals, and even thinner than thought atmosphere reported by Mariner 4 surprised and disappointed a lot of people. They were hoping for a world with at least some capability to support life. There weren't even any signs of ruins from an ancient civilization!

As we would discover less than a decade after the famous flyby, the robot probe missed a lot of the really amazing things on the Red Planet:

http://www.solarviews.com/cap/mars/mar4geom.htm

Some very informative sites on the mission:

http://www.petermasek.info/mariner4.html

http://home.earthlink.net/~nbrass1/mariner/miv.htm

http://en.wikipedia.org/wiki/Mariner_4

http://www.astronautix.com/craft/marner34.htm

http://www.solarviews.com/eng/marin4.htm