Evidence for water on Mars grows stronger

• Ten months after NASA's twin rovers landed on Mars, scientists reported this week that both robotic vehicles are still navigating their rock-studded landscapes with all instruments operating, and both are discovering fresh evidence that water must have helped to sculpt the terrain they are exploring.
• In a progress report for reporters, the rovers' science team leaders and chief engineer said the vehicle known as Spirit, which is climbing a low range of ancient hills above the younger lava plains of Gusev Crater -- and finding layered bedrock all along the way -- is facing a few problems of "middle age" but otherwise functioning excellently.
• Halfway across the planet, the rover known as Opportunity has just been steered safely across a steep and treacherous patch of sand pits that at times sank the vehicle's six wheels nearly hub-deep.
• The rover is now on its way up the sides of Endurance Crater toward an intriguing cliff that may reveal more evidence of water that soaked the rocks there billions of years ago, astronomer Steven Squyres of Cornell University, the project's chief scientist, said during the telephone briefing.
• The Earth-bound engineers who drive the distant rover by computer from Mission Control at the National Aeronautic and Space Administration's Jet Propulsion Laboratory in Pasadena, Calif., have done "an extraordinary job" in navigating Opportunity up the 25-degree crater wall, Squyres said.
• This, at least, is the best current scenario for the history of the hills, Arvidson said, although some of his colleagues are arguing that the shape of the features might have been formed by wind or even by rocky material that fell to the surface after it was ejected from some ancient crash of a comet or asteroid.
• Rock after granular rock along Spirit's path has shown similar layers separated by spaces where erosion has scoured out softer materials, Arvidson said.