Curiosity Stamps JPL Morse Code on Mars to Track 50-Centimeter Wheel Slip

2 articles · Updated · spacedaily.com · Aug 8

Curiosity has imprinted “JPL” in Morse code into Martian soil since its first 2012 test drive, using cut-outs on all six wheels as a built-in navigation marker rather than just an engineer’s joke.
Each 50-centimeter wheel leaves the pattern once per full rotation on soft ground, giving the rover a known visual reference when smooth terrain lacks enough rocks or shadows for reliable tracking.
JPL’s navigation software compares wheel rotations with gyroscope, accelerometer and before-and-after image data; if the stamped tracks show less progress than the wheels report, the rover can detect slip in sand or on slopes.
The feature is integrated into wheels with aluminum skin just 0.75 millimeters thick, underscoring how a playful signature also had to justify its mass and survive years of damage from sharp Martian rocks.
The design captures a broader Mars-rover constraint: with no real-time driver on Earth, Curiosity must leave visible evidence of its own motion and use that evidence to verify where it actually went.