NASA's Curiosity rover is still uncovering new headscratchers for its science team as it finishes up exploration at its second drill site, nicknamed Cumberland. Figuring out the composition of a dark rocky exposure the rover recently photographed will be one of its last tasks before heading on to the base of its eventual target, Mount Sharp.

"It’s a nice mystery," said Joy Crisp, deputy project scientist for the mission, during a NASA press briefing about Curiosity's most recent findings on June 5. The unknown rock, located at an area nicknamed Point Lake, has an odd "Swiss cheese texture" and appears more resistant to erosion than surrounding materials.

The science team thinks the outcrop is either volcanic or sedimentary. It could be the result of a lava flow, with holes left behind by gas bubbles, called vesicles. If it's sedimentary rock, the holes may have been left behind by a softer mineral that was etched out by wind, or caused by gases that were present in the rock when it formed. Curiosity is set to drive up to the rock and inspect it closely.

The rover will complete two more tasks at Cumberland: examining an area known as Shaler, an exposure likely representing a stream deposit, and measuring the hydrogen abundances in different rocks to determine their water content. Shaler is a 15-meter-wide exposure that preserves underwater dunes from the bottom of a Martian river billions of years ago. Closer inspection can tell scientists how fast and deep the flowing water might have been. Using its DAN instrument, Curiosity will record the presence of hydrated minerals in different rock layers, to show how water content changed over time.

But the team is eager to get driving and arrive at Mount Sharp, which researchers hope will reveal the rich history of Mars and how it changed from a warm, wet world to a cold and dry one. Researchers will meet in coming weeks to plan out their route and hope to do great science in the 8 kilometers between their present location and the mountain's base.

Scientists will use satellite data to "create menu of possible stopping points," said Jim Erikson, lead project manager, during the conference. Engineers are also looking forward to having the rover get some views where they can spot the discarded machinery that helped bring Curiosity to the surface.

Curiosity is expected to take at minimum eight to 10 months to reach Mount Sharp, though the science team said they might make further stops along the way if they see something interesting. The rover has already tested out all of its tools and techniques, including two successful attempts at drilling, and engineers have learned a great deal about how its systems work. For instance, the second drilling operation took only one-quarter the time of the first and further experience will help explore faster.