Sand dunes in Proctor Crater on Mars! I think it’s nifty that we know westerly winds helped shaped these dunes. As for that second image, there’s a comet the size of a small mountain swinging by Mars today. NASA (and India!) are hiding their satellites on the opposite side of the planet to avoid getting hit by pieces of dust. The Planetary Society’s Emily Lakdawalla will offer plenty of updates and live streams to watch the comet pass Mars.