CuriousMars: Curiosity's Critical Rock Drilling Target Selected as Opportunity Achieves Major Science Goal, SpaceRef

"After weeks of searching, the Mars rover Curiosity's science and engineering teams have selected a fine-grained slab of Martian rock as the candidate target for the first rock drilling on Mars, a significant first in planetary exploration."

"The rock was selected Jan. 7 based on data about its composition, hardness, likelihood of generating powder needed to coat internal surfaces, and the safety of the drilling mechanism and rover when drilling this particular slab."