Candidates for exploring Mars

Four innovative exploration programs vie for the honor of going to Mars. The Ares, a 350-lb composite aircraft designed for exploring Mars, measures roughly 15 ft long with a 20-ft wingspan. It will fly 300 mph (ground speed) at an altitude of 3,300 ft. When it goes to Mars, it will sport a dull white coating that accommodates thermal considerations, not the red, white, and blue paint scheme used to attract attention at a World Space Congress in Houston. Phoenix, the first interplanetary ditch digger, is designed to excavate a trench on Mars, then search soil samples from various depths for signs of water and life. A stereoscopic camera will guide the lander's robotic arm as it digs. The camera also has filters that will let it measure the opacity of the dusty sky. Marvel will orbit Mars, using a spectrometer to look at particles in the atmosphere as the setting or rising sun shines through them. The sunlight will let the spectrometer analyze the particles' chemical compositions and concentrations. In addition to spectro-meter data it collects, Ares will also send back to Earth a stream of measurements on parameters such as air pressure and density, temperature, and wind speed and direction during its flight. Scim may launch in 2007, fly its "swoop and scoop' mission through the Martian atmosphere in 2009, then return to Earth in January 2011. Scim will use a carbon-carbon composite aeroshell that can withstand the heat generated while entering the Martian atmosphere. The shell also won't shed particles that could contaminate dust samples collected. NASA plans on launching its first Mars Scout mission in 2007 at a cost capped at $325 million. But what that mission will actually be is still unknown. It's up to a jury of experts to choose from among four mission concepts: Phoenix, Marvel, Ares, and Scim. May the best concept win. Phoenix, a project headed by Peter Smith at the University of Arizona Lunar and Planetary Lab, uses technology developed for the 1999 Mars Polar Lander, which disappeared on descent to Mars. From the ashes of that program, researchers will resurrect and reuse a stereo-imaging camera and robotic arm. It will also carry a thermal-gas spectrometer. A Delta II rocket will send the Phoenix to Mars, where it will aerobrake into the atmosphere,