HiRISE: ‘Elementary, my dear deposit…’

Just like Earth, Mars experiences seasons that change as the planet orbits the Sun. Seasonal changes are most apparent at the higher latitudes. As these regions in each hemisphere enter their respective summer seasons, the sun rises higher in the Martian sky causing frost and ice to sublimate, and illuminate more features across the landscape. As the high latitudes of each hemisphere move toward their respective winters, the days (called “sols”) grow shorter and the sun hangs low on the horizon, giving rise to prolonged periods of cold, darkness, and frost accumulation… [More at link]