Mercury DOES have volcanoes.
More Info: When the Messenger spacecraft returned photos of the surface of Mercury, scientists found images that suggest the presence of many volcanoes on the surface of the planet. However, these volcanoes are all extinct and have been for perhaps billions of years.
Evidence of Volcanic Activity
The images from Messenger show many features that appear to have been caused by volcanic activity. There are irregular depressions on the surface that are more consistent with volcanic vents than with meteoric impact. Craters tend to being more regular and circular, so it is unlikely these features were caused by celestial collisions. Scientists can also see what appears to be evidence of lava flows surrounding those vents. Also, Mercury has many impact craters on the surface, and some of them appear to have had lava flows partially fill them after the impact.
Evidence of Tectonic Activity
Scientist also found pictures of long ridges on the surface of Mercury, probably dating from the time when Mercury was volcanically active. When the crust and mantle cooled on top of the molten core, the planet would have contacted, buckling and cracking as it cooled, causing these long mountainous ridges.
Mercury Volcanically Dormant Now
However, none of the images from Messenger show any signs of recent volcanic activity. All the visual evidence appears to be from the far distant past. Scientists are still debating how far distant. Some believe that the activity was from the very formation of the Solar System, so about 4 billion years ago. However, some scientists have found evidence from a huge impact crater that appears somewhat more recent, so they believe that Mercury could have had some volcanic activity as recently as 1 to 2 billion years ago. In either case, the volcanic stage of Mercury’s life has long since past. There are presently no active volcanoes on the surface of Mercury.
“Does Mercury Have Volcanoes?.” Universe Today — Space and astronomy news. N.p., n.d. Web. 3 Dec. 2012. http://www.universetoday.com/14341/does-mercury-have-volcanoes/
“Does Mercury Have Volcanoes? – OPT Telescopes.” Celestron Telescopes, Takahashi, CCD Cameras, Eyepieces, Meade – OPT Telescopes. N.p., n.d. Web. 3 Dec. 2012. http://www.optcorp.com/edu/articleDetailEDU.aspx?aid=896