Both reached Mars, and Global Surveyor is sending back reams of scientific data and images. In a few weeks, it will try taking pictures of where scientists think the lander went down, to search for its parachute, its shiny heat shield or maybe even the small lander itself. Climate Orbiter was launched in December 1998 and Polar Lander in January 1999. The next pair are scheduled to launch in 2001. The lander will carry a robotic arm to dig trenches for soil studies, as Polar Lander was supposed to do, and a spare of the rover that was so popular on the Pathfinder mission.
Subsequent missions are even more challenging.
Current scheduling calls for the 2003 mission to collect rocks on the surface of Mars, then blast them back into orbit around the planet. The 2005 mission, a joint effort with France, will fly to Mars, put more samples in orbit, pick up those and the earlier samples, and fly the whole collection back to Earth, arriving in 2008. Each mission will have to fit within the Mars exploration budget. In the early days of Mars exploration, the answer to failure was backups. NASA's first landing on Mars was the first of the twin Viking missions of 1976.