Tucson wasn't the only place that had a nice, white frosting in recent days. The UA's HiRISE camera, aboard the Mars Reconnaissance Orbiter, snapped this gorgeous photo of the frost melting in a Martian gully a few weeks ago. HiRISE researchers note: "At this time of year only south-facing slopes retain the frost, while the north-facing slopes have melted. Gullies are not the only active geologic process going on here. A small crater is visible at the bottom of the slope.