Curiosity landed on Mars on Aug. 5, 2012. It's now four years old.
So it's singing "Happy Birthday" to itself, using tools designed to analyze samples of Mars' dirt.
There won't be a Martian birthday party. The current population of Mars is just two — robots.
Curiosity's nearest friend is Opportunity. It's on the other side of the planet.
This video includes clips and images from NASA.