On the Cover: The Mars Exploration Rovers, <i>Spirit</i> and <i>Opportunity</i>, were designed to last three months on the surface of the Red Planet. Three years and more than 180,000 images later, these hardworking robotic explorers are still making thrilling discoveries. <i>Opportunity</i>'s Panoramic Camera (Pancam) imaged these sand dunes at the bottom of Endurance crater on sol (Martian day) 211. Some of these dunes are more than a meter tall from crest to trough. The image is processed in false color for mineral analysis.
4 The Pioneer Anomaly—A Mystery of Cosmic Proportions: Bruce Betts looks at the clues in this landstanding cosmic mystery.
16 Spirit and Opportunity—Martian Geologists: Matt Golombek gives an update of these amazing little rovers that could.
17 World Watch Save Our Science campaign; race to the Moon; Phobos-Grunt mission update
18 We Make it Happen! Winners of the 2007 Shoemaker NEO Grants
20 Q&A How long does it take for a comet to "die?" How thick is the ice on Europa?
21 Factinos Extrasolar planets "viewed" by Hubble and Spitzer
22 Society News 2007 Awards Celebration; Bill Nye goes to India