The Spirit and Opportunity rovers have each entered a new stage of exploration on Mars.

"We have arrived," said Mark Adler, Spirit mission manager at JPL, as the robot reached its destination. Spirit has wheeled across Gusev Crater some two miles distance from its original landing zone in January.

"Were there. Were at the hills now and already see new things there that we havent seen before," Adler told SPACE.com. At what is called West Spur, the rover is being steered slightly up the hill to inspect various targets, he said, including one rock labeled "Pot of Gold".

Scientists are eager to scour the area for evidence of possible ancient water activity.

The long-term plan for Spirit is to drive south, along the base of the Columbia Hills to a spot labeled "Lookout Point" -- about 50 feet (15 meters) up the feature. At that location, Spirit will have a tourist-like panoramic view, even grabbing camera shots of whats behind the hills for signs of layering.

At the Endurance Crater at Meridiani Planum -- a stadium-sized hole in the martian surface -- Opportunity is purring along, carefully making its way down the steep crater wall.

While some wheel slippage is being seen as expected, Adler added: "Well be able to dive in and drive out of the craterno problem."

After wheeling over the craters rim, Opportunity drove about 20 feet (6 meters) before stopping at a rock. That feature is being studied to contrast its geological makeup with data accumulated at Eagle Crater, acquired by the robot where it first landed.

At Eagle Crater the rover found small-scale rock textures and evaporite mineral compositions, showing that a body of salty water covered the site long ago.

Rock layers deep within Endurance are thicker and older than those inspected at the shallow Eagle Crater - the main scientific temptation for dispatching Opportunity to wheel inside the feature. By scrutinizing deeper rock layers, the environment of an earlier Mars could be revealed.

From its current position, Opportunity is to continue its drive about 10 feet (3 meters) deeper into Endurance Crater, arriving at a pre-selected primary science target by Tuesday.

"Of course, the scientists are already looking past that," Adler said. "If they want us to keep going, well evaluate if its safe and the slopes are good, and the rocks are still providing the kind of traction that we need," he stated.

Adler said that Opportunitys robotic arm, tipped with science sensors and a Rock Abrasion Tool (RAT), is evaluating the terrain the robot is about to drive upon. "We take it a step at a timefeeling out in front of us with the arm as we go down deeper into the crater."

Depending on what the roving Mars machine finds and observes within Endurance Crater, "well stay there as long as it takes to get the science we wantif we can do it safely," Adler said.

Adler said the Mars robots are performing well.

"Just in the past couple of days, both Opportunity and Spirit arrived at new places with new things to do. Its like their missions are starting over again," Adler said.

JPL robot experts are keeping an eye on a wheel motor on Spirit. Higher currents in that motor suggest friction is at work. "Were starting to take some actions and see what we can do about that," Adler said.

Around mid-September, the rovers will face minimum energy from a Sun low on the martian horizon. Sunlight is needed to power the robots through solar cell-laden wings mounted on each mobile spacecraft.

Robot handlers are scripting a plan for the rovers to "winter over" on Mars. "Somewhere around late August or sowe may want to get the rovers into a position where well maximize their solar energy," Adler said. "That means rolling them onto slopes, rocks, or hills such that the solar panels are tilted towards the north, where the Sun is at that time."

By angling rover solar panels toward the north through September and October, the robots are expected to be up and operating by late October or November, Adler said.

Mars Rovers: Complete Coverage

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