NASA’s Mars Exploration Rover Opportunity captured a view of wispy afternoon clouds, not unlike fair weather clouds on Earth, passing overhead on the rover’s 956th sol, or Martian day (October 2nd, 2006). With Opportunity facing northeast, the clouds appear to drift gently toward the west in the movie taken with the rover’s navigation camera. The 10 frames, taken 32 seconds apart, show the formation and evolution of what are likely mid-level, convective water clouds.
https://photojournal.jpl.nasa.gov/catalog/PIA09170