Mars [ http://www.challeng ], the freeze-dried planet [ http://nssdc.gsfc.n ], orbits 137 million miles from the Sun or at about 1.5 times the Earth-Sun distance [ http://antwrp.gsfc. ]. It has two diminutive moons [ http://antwrp.gsfc. ], towering extinct volcanos [ http://antwrp.gsfc. ], an immense canyon system [ http://antwrp.gsfc. ], a thin atmosphere chiefly composed of carbon dioxide (CO2), a frigid average surface temperature of -63 degrees Celsius [ http://www.unidata. ], and permanent frozen CO2 polar caps which contain some water ice. Mars' surface presently lacks liquid water [ http://antwrp.gsfc. ] and has a reddish color because of an abundance of oxidized iron compounds (rust). A small terrestrial planet [ http://www.seds.org ], fourth from the Sun [ http://antwrp.gsfc. ], Mars has only about 3/8 the surface gravity of Earth. So for example, if you tip the scale at a hefty 200 pounds on Earth you'd be a 75 pound featherweight on Mars [ http://quest.arc.na ]. The low martian gravity will be good for NASA's Mars Pathfinder [ http://mpfwww.jpl.n ] spacecraft scheduled to land on Mars [ http://bang.lanl.go ] next Friday, July 4th [ http://www.lpl.ariz ]. Using rockets, parachutes, and airbags [ http://mars.sgi.com ], Mars Pathfinder [ http://mpfwww.arc.n ] will be the first spacecraft to touchdown on the planet since the Viking landers [ http://antwrp.gsfc. ] in 1976. Pathfinder is also scheduled to begin the first ever mobile surface exploration [ http://cmex-www.arc ] by releasing the robot rover [ http://ranier.hq.na ], "Mars Sojourner" [ http://mars.sgi.com ].