Did you ever wonder how these satellite images reveal changes in sea ice? Even though water and ice have the same chemical formula (H2O) they have a different chemical structure and physical properties. Ice has a crystalline structure that reflects most of the visible energy that falls on it, making ice appear bright in satellite images from the visible spectrum. Clear water on the other hand tends to absorb most of the visible energy that strikes it, making water appear relatively darker than ice on the same image. This contrast in the behavior of water and ice can be seen as variations in tone (gray shades) on a satellite image.