This week's YouTube Saturday sees NASA astronomer Carolyn Crow explain her recent discovery that will help identify characteristics of extrasolar planets in the future. By comparing the reflected red, blue, and green light from planets in our solar system, they and their team were able to group the planets according to their similarities. The planets fall into very distinct regions on this plot, where the vertical direction indicates the relative amount of blue light, and the horizontal direction the relative amount of red light. In the future this could help identify Earth like planets before we have the telescope technology to see them in detail. A very simple but interesting discovery.