The Four Coolest NASA Robots

NASA may be known for sending men to the moon, establishing the International Space Station, and planning for a base on Mars--but apart from astronauts, its best known spokesmen aren't men at all--they're robots. Rovers like Spirit, Opportunity, and Curiosity, and landers like Viking and Philae, make the perfect ambassadors into hostile, freezing, and nearly airless environments. Not only do these explorers bring back valuable scientific data from Earth's planetary neighbors, they also make perfect showcases for practical robotics. Venus is no one's idea of a vacation home. Its atmosphere is a mixture of sulfuric acid and carbon dioxide, and with a surface temperature of 863 degrees Fahrenheit, only the toughest machine could possibly survive on its surface.