Introduced by one of the story's characters:
I’m Mars Opportunity Rover, Oppy for short. I used to work on the planet Mars, back in the 21st century, collecting data for an organisation on Earth called NASA. At least I did until the day I no longer had any energy to continue and I powered off.
You may find it strange that I can speak - it was never one of my abilities one hundred thousand years ago, but some cosmic archaeologists uncovered me and made some adjustments.
Would you like to know what happened then?”