(Sen) - NASA's Curiosity rover has found evidence that is has been driving along an ancient streambed. The rover has been taking pictures of stones cemented in rocks which scientists believe can only have been shaped by flowing water over a long period of time.
Curiosity's mast camera has focussed on two rocky outcrops that the Mars Science Laboratory team named after a rock formation and lake in Canada, Link and Hottah. The rocks contain stones ranging in size from a grain of sand to a golf ball, some are angular in shape but many are rounded. Scientists studying the images have concluded that in the ancient past the stones were carried by water downslope from the rim of Gale Crater and spread out in an alluvial fan in the base of the crater.
"From the size of gravels it carried, we can interpret the water was moving about 3 feet per second, with a depth somewhere between ankle and hip deep. 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. This is a transition from speculation about the size of streambed material to direct observation of it" explained William Dietrich, Curiosity science co-investigator.
A tilted block of ancient streambed on Mars, named Hottah. Credit: NASA/JPL-Caltech/MSSS
Rebecca Williams of the Planetary Science Institute commented "The shapes tell you they were transported and the sizes tell you they couldn't be transported by wind. They were transported by water flow."
Curiosity Project Scientist John Grotzinger of the California Institute of Technology summarised the significance of the discovery: "A long-flowing stream can be a habitable environment. It is not our top choice as an environment for preservation of organics, though. We're still going to Mount Sharp, but this is insurance that we have already found our first potentially habitable environment."
Curiosity, which landed on Mars on August 6, is making its way from its landing site in Gale Crater to the slopes of Mount Sharp in the middle of the crater. Its first destination has been named Glenelg which is about 400 metres from where the rover was put down. Glenelg is a natural intersection of three kinds of terrain including layered bedrock. When Curiosity gets there it will be the first rover ever to drill for a rock sample.
Curiosity has an initial two year mission (one Martian year) to find evidence if Gale Crater was ever suitable for microbial life. The rover has ten scientific instruments as its disposal.
NASA's Mars Science Laboratory, also known as Curiosity, landed on Mars on August 6 (UTC). NASA's Jet Propulsion Laboratory (JPL), based in Pasadena, California, a division of the California Institute of Technology, manages the Mars Science Laboratory mission for NASA.