During 14 years of intrepid exploration across Mars it advanced human knowledge by confirming that water once flowed on the Red Planet - but NASA's Opportunity rover has analysed its last soil sample. The robot has been missing since the US space agency lost contact during a dust storm in June last year and was declared officially dead on Wednesday, ending one of the most fruitful missions in the history of space exploration. Unable to recharge its batteries, Opportunity left hundreds of messages from Earth unanswered over the months, and NASA said it made its last attempt at contact. "I declare the Opportunity mission as complete," Thomas Zurbuchen, associate administrator of NASA's Science Mission Directorate told a news conference at mission headquarters in Pasadena, California. The community of researchers and engineers involved in the programme were in mourning over the passing of the rover, known affectionately as Oppy. "Spent the evening at JPL as the last ever commands were sent to the Opportunity rover on #Mars," Tanya Harrison, director of Martian research at Arizona State University, tweeted after a stint at Pasadena's Jet Propulsion Laboratory.