March 9, 2004 — This mosaic of four individual frames taken by Spirit's Microscopic Imager was carefully stitched together to reveal the entire 5-centimeter-diameter (almost 2-inch) hole left on the rock dubbed Humphrey. The holes were created by the Rock Abrasion Tool. Scientists are interested in many of the small features revealed on Humphrey. The sinuous veins within the rock could be evidence that water was trickling through the material while it was deep underground, and the dark spots in the center of the hole may be crystals of the mineral olivine.