"The loss of Mars' atmosphere has been an ongoing mystery. Doug McCuistion, director of the NASA Mars Exploration Program NASA has given a thumbs-up in its mission confirmation review process for the Mars Atmosphere and Volatile Evolution (Maven) project, heading it toward a 2013 launch. The spacecraft will orbit the planet and probe its upper atmosphere to study its interactions with the solar wind. Its aim is to learn more about the disappearance of the atmospheric shield that once allowed liquid water to flow across Mars's ruddy surface. The dry riverbeds that give evidence of this activity riddle the planet, but their last trickles seem to have evaporated billions of years ago.The thinking is that Mars "bleeds" its atmosphere because it is not dense enough to protect against the solar wind. Hence, a warmer and denser atmosphere that could shield the water has been lost. A later mission in 2016 The ExoMars Mars Climate Sounder instrument on NASA's Mars Reconnaissance Orbiter will map the vertical distribution of temperatures, dust, water vapor and ice clouds in the Martian atmosphere as the orbiter flies a near-polar orbit searching for faint gaseous clues about possible life on Mars. Two of the other selected instruments are spectrometers - one each from Europe and the United States - designed to detect very low concentrations of methane and other important trace gases in the Martian atmosphere. "To put the trace-gas measurements into context, you need to know the background structure and circulation of the atmosphere," said JPL's Tim Schofield, principal investigator for the ExoMars Climate Sounder. "We will provide the information needed to understand the distribution of trace gases identified by the spectrometers. We'll do this by characterizing the role of atmospheric circulation and aerosols, such as dust and ice, in trace-gas transport and in chemical reactions in the atmosphere affecting trace gases." The ExoMars Climate Sounder is an infrared radiometer designed to operate continuously, day and night, from the spacecraft's orbit about 400 kilometers (about 250 miles) above the Martian surface. It can pivot to point downward or toward the horizon, measuring temperature, water vapor, dust and ices for each 5-kilometer (3-mile) increment in height throughout the atmosphere from ground level to 90 kilometers (56 miles) altitude. "We'll fill in information about variability at different times of day, and we'll add to the number of Mars years for understanding year-to-year variability," said Schofield. "The most obvious year-to-year change is that some years have global dust storms and others don't. We'd like to learn whether there's anything predictive for anticipating the big dust storms, and what makes them so variable from year to year." An additional research goal is to assist future landings on Mars by supplying information about the variable density of the atmosphere. At a chosen landing site, atmospheric density can change from one day to the next, affecting a spacecraft's descent. "We want to provide background climatology for what to expect at a given site, in a given season, for a particular time of day, and also nearly real-time information for the atmospheric structure in the days leading up to the landing of a spacecraft launched after 2016," said Schofield. Mars has been balding like a middle-aged banker for some time now, a presumably thick and lustrous atmosphere which allowed surface water having been lost some time ago. Just why this should have happened, and what the current rate of loss is, are questions the ExoMars will hope to find answers to.One theory is that Mars lost its magnetic field, without which it was defenseless against the brutal onslaught of solar radiation which stripped anything not nailed down (like air) off the planet. Casey Kazan Sources: http://www.dailygalaxy.com http://www.jpl.nasa.gov/news/news.cfm?release=2010-280 http://www.nasa.gov/maven.
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