WASHINGTON, May 6 -- U.S. space agency NASA said Tuesday its Curiosity rover has completed its third drilling into a Martian rock and is now preparing to use its internal instruments to study the collected powdered sample.

Images sent back by Curiosity early Tuesday showed a fresh hole next to a shallow test hole the rover made a week ago in the target sandstone rock, dubbed "Windjana."

The new hole is 0.63 inch (about 1.6 centimeters) in diameter and about 2.6 inches (about 6.6 cm) deep, NASA said.

"The drill tailings from this rock are darker-toned and less red than we saw at the two previous drill sites," Jim Bell of Arizona State University, deputy principal investigator for Curiosity's Mast Camera (Mastcam), said in a NASA statement. "This suggests that the detailed chemical and mineral analysis that will be coming from Curiosity's other instruments could reveal different materials than we've seen before."

The mission's two previous rock-drilling sites, at mudstone targets in the Yellowknife Bay area, yielded evidence last year of an ancient lakebed environment favorable for microbial life billions of years ago.

The rover is currently at a location called "The Kimberley," about four kilometers southwest of Yellowknife Bay, and along the route toward the mission's long-term destination on lower slopes of Mount Sharp.

NASA said sample material collected from Windjana will be sieved, then delivered in coming days to onboard laboratories for determining the mineral and chemical composition.