A.J.S. RaylJan 19, 2004

Spirit Ventures Out to First Target

Opportunity Adjusts Flightpath

Spirit ventured out yesterday, driving nearly 10 feet (about 3 meters) to its first target -- a football-sized rock that scientists have dubbed Adirondack.

The Mars Exploration Rover flight team at the Jet Propulsion Laboratory (JPL) will send commands to Spirit early tomorrow to examine that target rock, Mission Manager Mark Adler announced today. The robot field geologist will inspect Adirondack with the microscopic imager, as well as the Mössbauer spectrometer and alpha particle X-ray spectrometer, both of which reveal the composition of rocks.

Adirondack is now about one foot (30 centimeters) in front of the front wheels.

Spirit successfully rolled off the lander and onto the Martian surface last Thursday and spent two and a half sols -- or Martian days -- inspecting the area, just a few feet from the lander, which has been renamed the Columbia Memorial Station.

Spirit is studying the rocks on Mars because they are, in essence, geological time capsules containing evidence of the environmental conditions of the past, Dave Des Marais, a rover science-team member from NASA Ames Research Center, noted at the daily news briefing this morning.

To get to Adirondack, Spirit turned 40 degrees in short arcs totaling 3.1 feet (95 centimeters), then turned in place toward the rock and drove straightforward in four short moves -- a total of 6.2 feet totaling 6.2 feet (1.9 meters). While the moves covered a span of 30 minutes, much of that time she was sitting still and taking pictures, with only about two minutes devoted to actual driving.

"The drive was designed for two purposes, one of which was to get to the rock [and the other] to testing out how we do drives on this new surface," Eddie Tunstel, rover mobility engineer at JPL, explained to reporters at the daily news briefing. Determining such things as how much the wheels slip in the Martian soil will give the team confidence for more ambitious drives in future weeks and months "These are the sorts of baby steps we're taking," Tunstel said.

Scientists chose Adirondack to be Spirit's first target rock rather than another rock they dubbed Sashimi. Although Sashimi which would have been a shorter, straight-ahead drive, it appears to be dustier than Adirondack. A dust layer could hinder scientists' attempts to get good observations of the rock's surface. They need as 'clean' a target as possible to determine what chemical changes and other weathering might have impacted the rock.

In addition, Sashimi is more pitted than Adirondack, something that makes it a poorer candidate for the rover's rock abrasion tool (RAT), which scrapes away a rock's surface for a view of the interior. By getting inside a rock, scientists can learn about environmental conditions present when the rock first formed. Adirondack has a "nice, flat surface" well-suited to trying out the rover's tools on their first Martian rock, Des Marais said. "The hypothesis is that this is a volcanic rock, but we'll test that hypothesis," he said.

In coming weeks and months, Spirit will be looking for clues in rocks and soil to determine whether the past environment in Gusev Crater was ever watery and possibly capable of sustaining life.

Meanwhile, Spirit's twin, Opportunity, successfully completed its first trajectory correction maneuver (TCM) in four months last Friday, adjusting its flightpath by firing its thrusters in a carefully calculated sequence. The maneuver began with a 20-second burn in the direction of the axis of rotation, then included two 5-second pulses perpendicular to that axis. "We're on target for our date on the plains of Meridiani next Saturday with a healthy spacecraft," reported Mission Manager Jim Erickson.

The maneuver -- or TCM -- was designed to put it on course for the target. Prior to the thruster firings, Opportunity was headed for a landing about 239 miles (384 kilometers) west and south of the intended landing site, said Christopher Potts, deputy navigation team chief for MER.

Opportunity's schedule still includes two more possible TCMs, this Thursday, January 22, and Saturday, January 24, but the maneuvers will only be commanded if needed. As of right now, Opportunity is still slated to land at Meridiani Planum, the opposite side of the planet from Spirit, on Saturday at 9:05 p.m., PST on 12:05 a.m. Eastern Standard Time, and 5:05 a.m. Greenwich Mean Time.

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