After working tirelessly for 14 years on the surface of planet Mars, today marks the official end to the Mars Exploration Rover Opportunity mission. Last communication with the rover was already back in June 2018, but Opportunity never woke up again although mission managers tried many times.
A globe encircling dust storm which blasted our neighbour planet the 2nd half of 2018 might have been the final push for Opportunity. Too much dust on the solar panels might have prevented powering the batteries to keep Opportunity warm at night. When electronics get too cold, the semiconductor materials simply crack.
More information on the NASA website.