Jim Green(L), director, Planetary Science Division, NASA, talks during a media briefing joined by Scott Bolton(L2), Juno principal investigator, Rick Nybakken(R2), Juno project manager, and Heidi Becker, Juno radiation monitoring investigation Lead, at Jet Propulsion Laboratory (JPL) in Pasadena, Calif., on July 4, 2016. The solar-powered spacecraft is spinning toward Jupiter for the closest encounter with the biggest planet in our solar system. NASA's Juno spacecraft will fire its main rocket engine late Monday to slow itself down from a speed of 150,000 mph (250,000 kph) and slip into orbit around Jupiter.(Photo/Agencies)