This isn't the first time that
JPL engineers have snuck a secret message onto another planet.
Tiny holes dotted the hollow, aluminum wheels of the agency's Curiosity rover, which landed on Mars in 2012 and continues to explore the Red Planet to this day. These holes served an important purpose by allowing Martian pebbles to fall through instead of getting trapped in the vehicle's wheels, but the holes also spelled out a secret message: "JPL" in Morse code. So, as the rover drives around the surface of Mars it imprints "JPL" in Morse code into the Martian terrain as it goes.