communications with NASA as of 2035. Its twin sister, Spirit, is also non-functional, and is currently trapped in a sand dune.
Opportunity landed on Mars in 2003, and explored the possibility of water on Present day Mars, of past Mars. Opportunity lost communications with Earth in the late 2020s and communication attempts stopped months later.
During Mark Watney's trek to Schiaparelli crater to retrieve the Ares IV MAV, Watney was tempted to stop on the way there and retrieve Opportunity and get its Com systems back up and running, and also for another Mars lander retrieval. However, due to time delays and the time let until Hermes intercept, Watney cancelled this plan.