This hat is a salute to both the Curiosity Rover and the upcoming Mars 2020 rover. (The “empty” triangle under the back of the rover is the ground penetrating radar signal from a science instrument on the back of Mars 2020.) You can follow along with their adventures at https://mars.nasa.gov/

This hat is worked from the brim up. You can adjust the length of the brim and the size of the needles to make this more or less slouchy. Sorry, no gauge – I winged it.