The Mars Science Laboratory rover drilled a 0.6-inch-wide and 2.6-inch-deep hole into a rock named Cumberland, which sits about nine feet west of John Klein, the first rock sampled back in March. Ground into a powder, sieved, portioned and delivered to the lab instruments in the rover's belly, the clay-rich sample from John Klein turned up six crucial elements used in life on Earth — hydrogen, carbon, oxygen, nitrogen, sulfur and phosphorus — as well as a low-acidity, life-friendly environment.
Scientists had been hoping to find such signs in the layers of Mount Sharp, a 3-mile-high mound that sits in the middle of Gale Crater. But the researchers found the first sign of a habitable environment in Yellowknife Bay in March, less than half a mile from the landing site.
"We have found a habitable environment that is so benign and is so supportive of life that probably if this water was around and you had been on the planet, you would have been able to drink it," Curiosity's lead scientist, John Grotzinger, said at the time.
For their very first rock, the scientists wanted to take no chances, said Ashwin Vasavada, the mission's deputy project scientist.
"We chose a nice flat slab of rock, even though there's other places that have a lot more secondary alterations, like veins and concretions," he said.
Now the scientists want to be sure that they got it right the first time, Vasavada said in a recent interview. They planned to choose a rock very much like John Klein, but with a few more interesting features, Vasavada said.
Cumberland fits that bill; it's considered quite similar to John Klein, but bears mineral veins and spherical concretions that should reveal more about different "eras" in the Red Planet's watery history, Vasavada said.
The Mars team doesn't plan to stick around Cumberland for too much longer; after a few more observations, it will head on a months-long journey toward Mt. Sharp to answer more questions about Mars' geologic history.
[Updated: An earlier version of this post incorrectly said Curiosity will be heading on a journey toward Gale Crater; the rover will be heading toward Mt. Sharp, which sits in the middle of the crater.]