Pathfinder landed on the surface of Mars in 1997. The craft, launched on December 5, 1996, traveled for 211 days and 309 million miles to reach the surface of Mars. A small rover named Sojourner (named after Sojourner Truth) traveled about the surface and analyzed rocks and the surface of the planet. The two vehicles (both significantly outliving scientific estimates) sent back 2.3 billion bits of data before transmissions stopped on September 27, 1997. Children can view some of the images of Mars at: Pathfinder.
Viking I landed on Mars in 1976. Launched August 20, 1975, Viking I carried cameras, a seismometer, a magnet, and sensors for temperature, wind velocity, and pressure. The Lander began to send data 25 seconds after landing and continued to function until November 11, 1982. Children can learn more at: Viking I.
Phoenix was launched by NASA in 2007. The spacecraft landed on a polar region of Mars on May 25, 2008, and conducted tests on water and surface chemistry until November 2, 2008. Then the Martian winter set in, and the fragile equipment could no longer send data. Children could learn more at: http://phoenix.lpl.arizona.edu/kids.php.
Phobos, a moon of Mars, was discovered by Asaph Hall of the United States Naval Observatory in 1877. The moon was named after the Greek god Phobos, meaning fear. The small moon actually orbits Mars faster than Mars rotates. Experts believe Phobos may eventually break apart and form a ring around Mars. Children could learn more at: Phobos.
Viking I was launched in 1975. It landed on the surface of Mars on July 20, 1976. It transmitted photographs and data regarding weather and atmosphere until November 11, 1982. Children can learn more at: Viking I.