Colors and waves

A piece of Mars: Here are some lovely ripples on Mars. In the same field of ripples, there are large wavy white ones and small complex blue ones. Why are there two different types, made distinct by their color, size, and shape? Nobody knows, but it’s a good bet the sand grains that they’re made of have different sizes and composition. Regardless of why they look the way they do, they’re still quite pretty. (HiRISE ESP_026388_2300)