The Mars Global Surveyor went quiet on November 2nd, and the chance of restoring communications is slim. The spacecraft has been circling Mars for more than 10 year, about 8 years longer than anticipated, so we have been lucky to date. Mars is still covered by a variety of craft, including the Mars Reconnaissance Orbiter, Mars Odyssey, two Mars rovers, and Mars Express. The problem is believed to be a disabled solar power array. For more on the mission, visit this link.