... Comet Wild 2s Nucleus from Stardust . ... What does a comet nucleus look like? ... The icy centers of comets are usually hidden from Earth-bound telescopes by opaque dust and gas that boils off during approach to the Sun. ... The Apollo 12 mission was the second ever to land humans on the Moon. ... This year, humanity learned that the universe is 13.7 billion years old. ... A Dust Devil Crater on Mars . ... What caused the streaks in this Martian crater? ... Young Star, Dark Cloud . ...