Opportunity appears to have caught something erupting out of the ground in sol107:
are these co2 sublimation vents?
the two frames captured are
http://mars.lyleresearch.com/imagery/1P137691267EFF2222P2363L7M1.JPG.html
http://mars.lyleresearch.com/imagery/1P137691267EFF2222P2363R1M1.JPG.html