digging in a deeper trench sky ' s aerial arm connected with a hard area that has investigators worrying about the prospect of someday uncovering an icy layer . " we have dig a trench and uncovered a hard layers at the same depth as the frozen layer in our other digging , " said washington university robotic arm investigator for phoenix , ray arvidson . the arms tries at least three times to penetrate the slab , but was defeated . as a result the arm went into a holding shape , awaiting its next commands .
A robotic arm has been used for scientific discoveries.