NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif., welcomed more than 38,000 visitors to its universe on Saturday and Sunday. The annual open house featured tours, videos, live demonstrations and interactions with the scientists and engineers who are pushing the frontiers of space exploration.

Humans aren't well-suited to space exploration. Most wouldn't stand a chance against the 20-year journey to the edge of solar system, temperature extremes that could boil or freeze blood, hazardous atmospheres, crushing gravitational forces and other harrowing conditions. That's why JPL has developed a special fleet of robotic space explorers, such as the Mars Science Laboratory rover, scheduled to land on the Red Planet Aug. 5.

JPL is also prototyping additional rovers to explore distant planets, airships to fly through the atmospheres of Titan and Venus, and drills and probes to go underground on Mars and Europa.