This is a crack on the ice covering the Ada Hayden pond in Ames, taken two winters ago. Iowa can be quite cold in winter, with continuously sub-freezing temperature lasting for weeks in a row. I remember a three years ago I was at the January meeting of the American Astronomical Society, attending a talk about Mars climate. One of the slides had a plot showing summer weather on the red planet: it turned out that at that moment the temperature in Ames was actually lower than the daytime temperature experienced by the rovers roaming the equatorial zone on Mars! True to that, I had to extend my trip by one day, due to a snow storm that grounded all air transportation to the Midwest the day I was supposed to come back home. But do you know that we have observed snow falling on Mars?