The Curiosity rover will have been on Mars for four (Earth) years tomorrow, which means it’s time, yet again, for another lonely birthday celebrated on distance space rock with no one else around—except for the other rovers also left to live up there alone. In honor of those four years of incredible science on the Red Planet, let’s listen to the birthday song the rover sings to itself to mark its lonely passage of time.

The video above is from the rover’s first birthday, when some of its crafty human technicians back here on Earth decided to program one of its vibrating science instruments to play the tune to the happy birthday song. It’s fun to listen to, but it’s also a bit sad to imagine the same sound echoing around the empty Martian landscape.

The rover has grown up a lot over those four years of science and, in recent developments, sports its own racing video game and the ability to decide for itself what it wants to shoot its lasers at. (Luckily, it’s far away from any humans.) It’s also gotten a two-year mission extension to keep revealing more of the mysteries of its new home—and, by extension, our solar system—and NASA has put out a new video on all it’s accomplished so far.

Now we just have to wait until we can finally send humans up there to reunite with our lost robot compatriots. That’s definitely going to be a mission priority, right? I’m going to need video footage of astronauts greeting and petting the curiosity rover like an adorable robotic dog, or what is even the point of colonizing another planet?

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