NASA's Mars Science Laboratory rover Curiosity has a target for its first drill test - a flat rock shot through with lighter veins, believed to be calcium sulfate, which could be a clue about past water on the red planet.
On Earth, similar veins form when water flows through fractures in a rock, scientists told reporters during a conference call Tuesday.
Additional inspections will be made as the rover drives closer to the rock, which is named "John Klein" after a former deputy project manager who died in 2011.
If the engineering tests and surveys pan out, Curiosity will use its high-powered drill for the first time within about two weeks, said lead scientist John Grotzinger, with the California Institute of Technology.
The rover, which touched down on Aug. 6, 2012, inside a giant impact basin near the planet's equator, is five months into a planned two-year mission to determine if the planet most like Earth in the solar system has or ever had the chemical ingredients to support and preserve microbial life.
"Drilling into a rock to collect a sample will be this mission's most challenging activity since the landing. It has never been done on Mars," project manager Richard Cook, with NASA's Jet Propulsion Laboratory in Pasadena, Calif., said in a statement.
"We won't be surprised if some steps in the process don't go exactly as planned the first time through," he added.
Curiosity will first use the drill, located at the end of its 7-foot-long robot arm, to make a few test holes so any lingering contamination from Earth will be removed.
Later, samples will be taken from the rock and the vein and passed into the rover's onboard laboratory to determine their chemical and mineral composition.
Pictures show the area around the rock is filled with unusual features, such as veins, nodules, a pebble embedded in sandstone and maybe even some holes in the ground. Other data from orbit show the area cools off more slowly at night than surrounding terrain. Scientists have yet to learn why.
"This area had a different type of wet environment than the streambed where we landed - maybe a few different types of wet environments," Grotzinger said in a NASA press release.
Image: This image of an outcrop at the "Sheepbed" locality, taken by NASA's Curiosity Mars rover with its right Mast Camera (Mastcam), shows show well-defined veins filled with whitish minerals, interpreted as calcium sulfate. Credit: NASA/JPL-Caltech