LOS ANGELES, Sept. 1 (Xinhuanet) -- Sitting 82 meters above the Martian plain, the rover Spirit has returned images of stunning new vistas filled with evidence of the red planet's past environments, US space agency NASA reported on Thursday.

    "That's no Mt. Everest, but it's a heck of a climb for our little rover," said Steve Squyres, principal investigator of the rover's science mission. "When we first touched down at Gusev Crater on Jan. 4, 2004, the Columbia Hills looked impossibly far away."

    Spirit spent 591 Martian days roving across the 3 km between its landing point and the summit of Husband Hill, one of a network of rises in the Columbia Hills chain. One Martian day is about 24 hours and 40 minutes.

    The summit, 82 meters above the edge of the surrounding plains, is 106 meters higher than the site where Spirit landed nearly 20 months ago.

    "When the images came down and we could see horizon all the wayaround, that was every bit as exhilarating as getting to the top of any mountain I've climbed on Earth," said Chris Leger, a rover planner at NASA's Jet Propulsion Laboratory in Pasadena, California.

    The climb was motivated by science, said Squyres. "Every time Spirit has gained altitude, we've found different rock types. Also, we're doing what any field geologist would do in an area like this: climbing to a good vantage point for plotting a route."

    The crest of Husband Hill offers Spirit's views of possible routes into a basin to the south with apparently layered outcrops.Shortly after Spirit landed, it observed a cluster of seven hills east of its landing site. NASA proposed naming the range Columbia Hills in tribute to the last crew of Space Shuttle Columbia. The tallest of the hills commemorates Rick Husband, Columbia's commander.

    Volcanic rocks covering the plain Spirit crossed on its way to the hills bore evidence of only slight alteration by water. When Spirit reached the base of the hills five months after landing, it immediately began finding rocks with wetter histories.

    Researchers are viewing possible routes south to apparently layered ledges and to a feature dubbed "home plate," which might be a plateau of older rock or a filled-in crater.

    The landing site and the Columbia Hills are within Gusev Crater, a bowl about 150 km in diameter. The crater was selected as the landing site for the Spirit rover because the shape of the terrain suggests the crater once held a lake.

    Volcanic deposits appear to have covered any sign of ancient lakebed geology out on the plain, but scientists say the hills expose older layers that have been lifted and tipped by a meteorite impact or other event.

    "We're finding abundant evidence for alteration of rocks in a water environment," said Ray Arvidson, deputy principal investigator for the rovers' science instruments.

    "What we want to do is figure out which layers were on top of which other layers. To do that it has been helpful to keep climbing for good views of how the layers are tilted to varying degrees. Understanding the sequence of layers is equivalent to having a deep drill core from drilling beneath the plains," he added.

    Spirit and twin rover, Opportunity, successfully completed their three-month prime missions in April 2004. They have inspected dozens of rocks and soil targets since then, continuing their pursuit of geological evidence about formerly wet conditionson Mars.

    Now both rovers' solar panels are generating plenty of energy thanks to repeated dust-cleaning events. Spirit has driven 4,827 meters, and Opportunity 5,737 meters, according to the NASA's Jet Propulsion Laboratory. Enditem