Engineers and scientists working on NASA's Mars Exploration Rover project

Engineers and scientists working on NASA's Mars Exploration Rover project are in the final stages of readying the twin robots for launch and picking safe and scientifically rewarding landing sites on the Red Planet. During the past two years, Mars scientists have mulled over some 185 landing sites. They have debated the merits of each, and continue to wrestle with a matrix of maddening worries--from high winds, dust and swings of day/night temperatures to dangerous rocks that might cripple chances for successfully landing and operating the robots.

Four landing locales have been culled from Cartier Replica a huge list of promising sites. Each has its merits as well as drawbacks. First and foremost, of course, is the fact that if you don't land safely you don't get any science lack. This is in fact the first time that site selection has used science to triage landing sites on Mars," said John Grant, co-chair of the Landing Site Steering Committee.

Those landing locations are on the table because they address the science objectives of the rover missions: Determine if water was present on Mars and whether there are conditions favorable to the preservation of evidence for ancient life. Each wheeled rover carries the Athena package of science gear. That array of equipment has undergone rigorous calibration and testing. Matching Athena's performance to the right site to maximize scientific output and achieve testing of scientific hypotheses is crucial.

Each rover will have a primary mission lasting at least three months on the Martian surface. Manning served similar duty for the Mars Pathfinder/Sojourner rover mission that touched down on the Red Planet in July 1997. The project was less than three years from start to launch. Manning said, "We had to do so much over again. So many parts of the system we had to go back and re-engineer for this larger mass vehicle. For instance, the huge gaggle of airbags that cocoons each rover during hard landing has been dropped--tested some 50 times. Early tests proved worrisome--so much so that significant beefing up of the airbags was necessary. Similarly, there were a number of ill-fated tests of the MER parachute system. That too demanded considerable extra work to iron out a mission trouble spot."

For Jim Garvin, NASA lead scientists for Mars exploration. MER is the first real taste of the surface. The win rovers armed with the Athena Replica Hublot Watches science payload will calibrate the whole community on what Mars is truly like. He said, "I like to call rocks ' Mother Nature's artifacts'. I think what MER will give us is far less confusion about two very different types of sites. . What is this passage mainly about?