The French Impressionist artist Pierre-Auguste Renoir liked to paint outside, en plein air. The experience brought a freshness, an immediacy, to his canvasses. No matter how often he painted in the gardens of Giverny or in the forests of Fontainebleau, nature always provided surprises. In his diaries he commented, “You come to nature with your theories, and she knocks them all flat.” He could have been talking about planetary science.