Purple aurora in America

Not only the sky and the water, but even the trees on the slope around Lake Crater National Park, Oregon, the United States were also transformed by the presence of purple aurora in the evening of May 31. (Photo: National Geographic)

Titan, Saturn's largest satellite, is in a photograph taken by American ship Cassini. (Photo: NASA)

The American Swift satellite captures 655 images to survey stars in an area of ​​7,000 light-years in the Small Magellanic Cloud. After the computer grafted 655 photos together, the scientists obtained a piece of cake-like image with countless colorful sugar granules. (Photo: NASA)

The world's largest sea, the Aral Sea, appears in a photograph taken by American Landsat satellite. The black area is the water in the Aral Sea, and the white area is the clouds. Currently the water area in the Aral Sea is only 1/10 of the original. (Photo: NASA)

Like a peacock, the comet Pan-STARRS shows a fan-shaped tail in the universe. The tail is formed by comets spraying dust and gas into the surrounding environment. (Photo: National Geographic)

Black dust covers the western flank of Karimsky volcano on Russia's Kamchatka peninsula. US Landsat satellite captures this scene on May 20. (Photo: NASA)