A veined rock in Yellowknife Bay nicknamed "John Klein" will be the first drill site for the Curiosity rover. The area contains a wide diversity of rock types. NASA/JPL-Caltech/MSSS Three different rocks at the side are A, a "bread-crusted" rock, whose fractured surface suggests the outer part expanded relative to the interior. B is representative of the material that will be sampled at the John Klein site, showing both light-toned veins and dark spots. And C is an exotic black rock probably ejected by an impact. NASA/JPL-Caltech/MSSS A closeup image from the rover's Mars Hand Lens Imager (MAHLI), showing different grain sizes in the sedimentary rock. NASA/JPL-Caltech/MSSS The area that Curiosity is exploring, named Yellowknife Bay, contains rocks with veins of material, indicating flowing water in the past. NASA/JPL-Caltech/MSSS Lower and therefore older rocks in an outcrop nicknamed Sheepbed show cracks and veins filled with whitish minerals, interpreted as calcium sulfate. NASA/JPL-Caltech/MSSS A rock in Yellowknife Bay covered in small sphericules common on Mars, which formed in water that percolated through pores in the sediment. NASA/JPL-Caltech/MSSS This outcrop, nicknamed "Shaler," contains the fossils of underwater dunes that formed at the bottom of an ancient river on Mars. NASA/JPL-Caltech/MSSS

NASA's Curiosity rover has explored a new area on Mars called Yellowknife Bay, which shows plenty of evidence of flowing water. The rover is preparing to drill into a rock nicknamed "John Klein" in the location in the next couple weeks, investigating its composition and searching for organics. This will be the first time that engineers have drilled into the surface of another planet.

Scientists already know that Curiosity's explorations have taken it to a place that was basically an ancient riverbed. Now they are uncovering the complex geologic history of the area and have stumbled across many interesting features.

"The scientists have been let into the candy store," said engineer Richard Cook, project manager for Curiosity, during a NASA teleconference on Jan. 15.

For the last few weeks, the rover has been moving from the plateau it landed on down a slope into a depression. As it descended, it passed through layers of rock that are increasingly older, taking it backwards into the planet's history. Geologists are finding a lot of different rock types, indicating that many different geologic processes took place here over time.

Some of the minerals are sedimentary, suggesting that flowing water moved small grains around and deposited them, and other evidence suggests water moved through the rocks after they had formed. Tiny spherical concretions scattered through the rock were likely formed when water percolated through rock pores and minerals precipitated out. Other samples are cracked and filled with veins of material such as calcium sulfate, that were also formed when water percolated through the cracks and deposited the mineral.

"Basically these rocks were saturated with water," said geologist John Grotzinger of Caltech, Curiosity’s project scientist, who added that these rocks indicate the most complex history of water that researchers have yet seen on Mars.

Curiosity brushed some of these rocks to remove their dust covering and then peered at them close-up with its high-resolution Mars Hand Lens Imager (MAHLI) camera. The rocks are sandstones containing larger grains up to 2 mm long surrounded by silt grains that are "finer than powdered sugar but coarser than sugar used to make icing," said geologist R. Aileen Yingst of the Planetary Science Institute, a scientist on the MAHLI team.

Many of the grains are rounded, suggesting they were knocked about and worn down somehow. Because the grains are too large to have been carried by wind, they were most likely transported by water flowing at least 1 meter per second (2.2 mph). All these investigations suggest if you could go deep into Mars' past and stand at the same spot as the rover, you'd probably see a river of flowing water with small underwater dunes along the riverbed.

The next step for Curiosity is to drill 5 centimeter holes into some of these rocks and veins to definitively determine their composition. Grotzinger said that the team will search for aqueous minerals, isotope ratios that could indicate the composition of Mars' atmosphere in the past, and possibly organic material.

The drilling will probably take place within two weeks, though NASA engineers are still unsure of the exact date. The procedure will be "the most significant engineering thing we’ve done since landing," said Cook, and will require several trial runs, equipment warm-ups, and drilling a couple test holes to make sure everything works. The team wants to take things as slowly as possible to correct for any problems that may arise, such as potential electrical shorts and excessive shaking of the rover.