It also features abundant, berry-shaped spherules that scientists say are sedimentary concretions formed in and worked over by water.
All together, "basically these rocks were saturated with water," Dr. Grotzinger explained during a briefing Tuesday outlining the rover's latest exploits.
Yellowknife Bay represents "a jackpot unit," he added. Initially, researchers thought they might have to drive Curiosity up on the shoulders of Mt. Sharp, a towering summit in the middle of the crater, to find such a trove.
If Curiosity made these finds on Mt. Sharp, "we would have been absolutely thrilled," Grotzinger says.
Curiosity, a one-ton geochemistry lab on wheels, landed on Mars in August. Its goal is to see if the crater at one time could have been hospitable for simple forms of organic life. Curiosity has spent the past six months exercising its suite of 10 instruments and its seven-foot robotic arm in a series of tests aimed at ensuring all the hardware is working well before the rover heads for Mt. Sharp, its ultimate destination.
The rover probably won't begin to explore Mt. Sharp for another year.
Curiosity has traveled slightly more than a quarter of a mile, as the crow flies, since landing. Along the way, however, scientists have chosen targets for instrument tests that have already provided insights into the crater's geologic past – including evidence for an ancient stream bed.