Curiosity has driven a quarter-mile (416 meters) from Bradbury Landing, where it touched down in Mars's Gale Crater, on its way to Glenelg. The rover is about halfway to its first targeted science destination, but along the way has tested its robotic arm's instruments, gazed up at Mars' two moons and touched its first rock (named "Jake Matijevic" for the rover's surface operations systems chief engineer who died Aug. 20 at 64).
Curiosity also found evidence that a stream once ran vigorously across the area on Mars where it is driving.
There's earlier evidence for water on Mars, but this evidence, images of rocks containing ancient streambed gravels, is the first of its kind.
"We can interpret the water was moving about 3 feet per second, with a depth somewhere between ankle and hip deep," said Curiosity science co-investigator William Dietrich of the University of California, Berkeley. "Plenty of papers have been written about channels on Mars with many different hypotheses about the flows in them. This is the first time we're actually seeing water-transported gravel on Mars."
The discovery comes from examining two outcrops, called "Hottah" and "Link" with the telephoto capability of Curiosity's mast-mounted camera during the first 40 days after landing. Those observations followed up on earlier hints from another outcrop, which was exposed by Curiosity's landing thrusters.
"A long-flowing stream can be a habitable environment," Mars Science Laboratory project scientist John Grotzinger, with the California Institute of Technology in Pasadena, Calif., said. "It is not our top choice as an environment for preservation of organics... but this is insurance that we have already found our first potentially habitable environment."
Curiosity touched its first Martian rock, "Jake Matijevic," with its robotic arm on Sept. 22, assessing its chemical elements.
After a short drive to get within an arm's reach of the football-size rock, Curiosity put its Alpha Particle X-Ray Spectrometer (APXS) instrument in contact with the rock during the rover's 46th Martian day, or sol. The APXS is on a turret at the end of the rover's 7-foot (2.1-meter) arm. The Mars Hand Lens Imager (MAHLI), on the same turret, was also used for close-up inspection of the rock.
The Chemistry and Camera (ChemCam) instrument, which shoots laser pulses at a target from the top of Curiosity's mast, also assessed what chemical elements are in Jake Matijevic.
With a last laser test of the rock on Sol 48 (Sept. 24), Curiosity finished its work on the rock. The rover departed the same sol.
Two days before leaving its mark on Jake Matijevic, Curiosity returned a photo of a different type of signature: the autograph of the President of the United States.
The image revealed a 3.94 by 3.23 inch (100 by 82 millimeter) anodized aluminum plaque affixed to the rover's deck bearing several signatures
of U.S. officials, including President Barack Obama and Vice President Joe Biden.