On Mars, the wheels of Curiosity write three letters.

In the footsteps of Curiosity, some straight marks interrupt the zigzag drawing of the wheels. Their succession is not a manufacturing defect. It corresponds to three letters in Morse: J, P and L. The robot thus leaves a reference to the Jet Propulsion Laboratory, where it was designed and assembled.

The pattern appears on its six wheels. By driving on a field that retains the footprints, they reproduce the same code at regular intervals. The JPL, however, emphasizes a utility that goes beyond the signature: these marks provide benchmarks for the visual odometry system, a method of estimating displacement from images.

Wheel rotation and real progress are not always equivalent on loose ground. Having observable cues helps to track movement more accurately. These letters are therefore neither an address for potential inhabitants nor a natural alphabet discovered on the planet. They bring together a wink to the manufacturers and a concrete navigation function.