|Volume: 04, Issue: 01||09/07/2005|
Mars Mission Successes Delight ScientistsThe enigmatic Red Planet continues to intrigue and excite researchers through its latest Mars missions. As the Mars Reconnaissance Orbiter continues its long journey toward the planet, the durable Spirit rover is rewarding researchers with tempting scenes filled with evidence of past planet environments.
NASA’s Mars Exploration Rovers, Spirit and Opportunity, successfully completed their three-month prime missions in April 2004. Since then, they have inspected dozens of rocks and soil targets, continuing their pursuit of geological evidence of formerly wet conditions on Mars.
Spirit recently delighted scientists by climbing to the summit of Husband Hill. The hill crest offers views of possible routes into a basin to the south with apparently layered outcrops.
"When the images came down and we could see horizon all the way around, 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 (JPL).
The summit sits 269 feet above the edge of the surrounding plains and is 348 feet higher than the site where Spirit landed nearly 20 months ago. Shortly after landing, Spirit observed a cluster of seven hills about 2 miles east of its landing site. NASA named 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.
"This climb was motivated by science," said Steve Squyres of Cornell University, principal investigator for the rovers' science instruments. "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."
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 95 miles 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 of Washington University, 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."
Both Spirit and Opportunity have been extremely successful. Their solar panels are generating plenty of energy thanks to repeated dust-cleaning events. Spirit has driven 3.00 miles and Opportunity 3.56 miles.
Meanwhile, another NASA mission is heading for the Red Planet. The Mars Reconnaissance Orbiter successfully tested its main engines by making a successful trajectory adjustment to reach Mars on March 10, 2006.
The spacecraft fired all six main thrusters for 15 seconds on Aug. 27. The engine burn followed a 30-second burn of six smaller thrusters, which settled propellant in the craft's fuel tank for smoother flow. The spacecraft's orientation was adjusted prior to the burns to point the engines in the proper direction for the maneuver. The spacecraft returned to the regular cruise-phase attitude after the trajectory adjustment.
"This maneuver accomplished two goals at once," said Mars Reconnaissance Orbiter Deputy Mission Manager Dan Johnston of JPL. "It adjusted our trajectory toward our Mars target point, and it gave us a valuable checkout of the orbit-insertion engines."
The target point is 245 miles above the surface of Mars. Initial analysis of navigational data indicates this first flight path correction successfully changed the spacecraft's velocity by the intended 17.4 miles per hour. Mars Reconnaissance Orbiter's velocity relative to the Sun is 73,497 miles per hour.
The six main engines won't be used again until the craft arrives at Mars. The next burn will last about 25 minutes. It will slow Mars Reconnaissance Orbiter enough for the planet's gravity to capture the spacecraft into orbit. Each main engine produces approximately 38 pounds of thrust. The three remaining opportunities scheduled for fine-tuning the trajectory before March will use smaller engines. Each smaller engine produces approximately five pounds of thrust.
The spacecraft was launched Aug. 12, and it is in excellent health. The Mars Reconnaissance Orbiter mission will examine Mars in unprecedented detail from low orbit. Mission science objectives include studying water distribution -- including ice, vapor or liquid – as well as geologic features and minerals. It will also support future missions to Mars by examining potential landing sites and by providing a relay for communications back to Earth.
For information about the MRO, visit http://www.nasa.gov/mro . For images and information about the Mars Exploration Rovers, go to http://www.nasa.gov/vision/universe/solarsystem/mer_main.html or http://marsrovers.jpl.nasa.gov.
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