NASA is about to launch a scientific laboratory to Mars that will be the first spacecraft to land in the northern polar region of the planet and dig for evidence of water or other conditions that could support some form of life. If the 770-pound spacecraft, Mars Phoenix Lander, touches down safely after its 10-month journey from Cape Canaveral, Florida on a Delta II rocket, it will spend three months or longer probing the ground and monitoring the weather above. Unlike rover missions that explore large areas, Phoenix is to stay on one spot in the permafrost region of the Martian arctic and use a mechanical arm to explore the area in detail. “This is a vertical mission,” said Peter H. Smith of the University of Arizona, the mission’s principal scientist. “We are going to dig down and not explore horizontally.” The target area is covered with polar ice in the winter, but Phoenix is to arrive in the summer when the ground is mostly clear. After landing, the robot spacecraft will unfurl a pair of circular solar power arrays that give it a width of 18 feet. It will deploy a pair of stereoscopic color cameras on a mast that extends 7 ft above the surface to record panoramic views, and extend a 4-ft mast bearing temperature sensors from an onboard weather station supplied by the Canadian Space Agency. The weather station, designed to operate even after the craft’s primary digging mission is completed, is to track daily and seasonal changes in temperature, atmospheric pressure and wind speed and direction. In addition, a pulsing laser will fire into the atmosphere to measure the size and altitude of dust and ice particles in the vicinity. With a 7.7-ft-long hinged arm that operates like a backhoe, the craft is to dig a series of trenches more than 20 inches into the ground with a moveable metal scoop that has sharp prongs and serrated blades on the end. At full range, the arm can reach 8 sq yards of surface area near the lander, Smith said. Guided by a camera on the end of the scoop, scientists will select soil and ice samples for detailed study by instruments on the lander. For one experiment, the Thermal and Evolved Gas Analyzer, samples will be dropped into a hopper to feed eight single-use ovens the size of an ink cartridge in a ballpoint pen. The sample will be slowly heated to 1,800 degrees Fahrenheit to study the transition from solid to liquid to gas, and the vapors analysed by a mass spectrometer to measure the mass and composition of specific molecules. Four other samples are to be examined in a miniature wet chemistry laboratory, where they will be stirred into a prewarmed solution and mixed with chemicals to tease out certain constituents, such as carbonates, sulfates and soil oxidants. Such components could either encourage or deter the formation of life if liquid water were available at times, scientists said. This laboratory also contains two microscopes to examine the fine structure of soil and ice samples, revealing features as small as 1/1,000th the width of a human hair that could be evidence of past liquid water on the planet.-WARREN E. LEARY (New York Times)
