PASADENA, July 7: The Sojourner Rover became the first mobile vehicle to roam another planet, rolling onto the dusty Martian soil into a diverse landscape bearing unmistakable signs of ancient water activity, the basic requirement for life on any planet.Hours after it rolled down a ramp from the Mars Pathfinder Lander on Sunday, the tiny rover began a new era of exploration of the red planet.``She is the robotic equivalent of Neil Armstrong on Mars,'' Rover scientist Henry Moore said proudly. ``She's your field geologist, and she wants to thank the people of the united states and all foreign contributors paying for her.''On Sunday afternoon, Sojourner sat just beyond the ramp, at the end of a distinct pair of tracks in the red dust. From studying the tracks, geologists said the surface seemed like a thin dusting of flour over a harder layer.By day's end, Sojourner was expected to have completed a 90-degree counterclockwise rotation, then backed up a few inches to put its alpha proton X-ray spectrometer in contact with `barnacle bill', a bumpy rock about the size of the rover. Already, mission scientists were beginning to do field geology by looking at the landscape in images transmitted from 192 million kms (120 million miles) away. A light-colored vertical mark on a hillside could be an avalanche gully, said University of Arizona geologist Ron Greeley. Horizontal features on another hill could be terraces cut by moving water, horizontal rock layers laid down in a lake or a bathtub ringlike feature left along an ancient shoreline.``These all are indicators of water activity,'' Greeley said.Because the search for life on Mars is the central theme of NASA's long-term Mars exploration strategy, much of Pathfinder is dedicated to determining whether water once flowed across the landing site, and if so, for how long. The ultimate goal is to understand the geologic history of the landing site which may take years of scientific wrangling.
