Although the Jet Propulsion Laboratory in Pasadena, California, has become synonymous with the United States' planetary exploration during the past half century, its most recent focus has been on Mars. Beginning in the 1990s and continuing through the Mars Phoenix mission of 2007, JPL led the way in engineering an impressive, rapidly evolving succession of Mars orbiters and landers, including roving robotic vehicles whose successful deployment onto the Martian surface posed some of the most comp