I just got confirmation that NASA has been using Python on board the Mars rover. NASA used Python to process images and videos taken during landing. The recordings were taken by USB camera and ffmpeg. The rover ran Python scripts to post-process the recordings before the information was sent to Earth.
You can find more information in the Linux Unplugged interview with Tim Canham from NASA JPL, LINUX Unplugged 396: How Linux Got to Mars
Original source: https://twitter.com/tjmcgrew/status/1370009196167626752