Scientists have cracked a long-standing Martian mystery. Those seasonal gullies on sand dunes that everyone thought were made by water. Turns out, carbon dioxide (CO₂) ice, or dry ice, is the culprit.

Winter means a lot of indoor time, and I've learned that science experiments are a lifesaver on those long, cold days. The best part? You don't need anything fancy. Baking soda, vinegar, food ...