Space.com: As of 15 December, NASA’s Odyssey orbiter became Mars’s longest-running mission. The satellite has been orbiting Mars for 3340 days, passing the record previously set by the Mars Global Surveyor. It was Odyssey that discovered water ice under Mars’s surface, only a few months into its mission. It also monitored Mars’s radiation levels to determine the feasibility of human exploration. Although Odyssey completed its primary mission in 2004, it continues to work, monitoring long-term climate patterns and capturing images of the planet’s surface to create a high-resolution global map.