This was due to the fluid injected into the rock flowing into a pre-existing natural crack in the rock, known as a fault, triggering a minor earthquake. (sciencedaily.com)
This study is the first to advise legislative bodies as there are currently no guidelines set for the horizontal distance required between the fluid injection points and pre-existing cracks in the rock. (sciencedaily.com)
These could be places where water flowed through cracks in the rock, leaving mineral deposits behind, although the rover has not yet measured their composition. (newscientist.com)