Perhaps try the BBC article: Mercury has been 'dynamic world' [bbc.co.uk]
"Many scientists believed that Mercury was much like the Moon - that it cooled off very early in Solar System history, and has been a dead planet throughout most of its evolution," said Maria Zuber, from the Massachusetts Institute of Technology (MIT).
"Now, we're finding compelling evidence for unusual dynamics within the planet, indicating that Mercury was apparently active for a long time."
Dr Zuber and her colleagues used laser measurements from Messenger to map out a large number of impact craters, and found that many had tilted over time. This suggests that geological processes within the planet have re-shaped Mercury's terrain after the craters were created.
A process called polar wander can cause geological features to shift around on a planet's surface.
In theory, the process of convection going on within the mantle could drive such changes. But Dr Zuber said this would be unusual in Mercury's case, because the mantle is so thin.
Another potential explanation could be that features on the surface were distorted as the planet's interior cooled and contracted. This fits in with observations that some surface features on Mercury have been exposed to high levels of stress.
Source: http://rss.slashdot.org/~r/Slashdot/slashdotScience/~3/HZM6WQWCZOI/mystery-rising-within-mercury
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