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NASA’s Juno Space Probe Makes It to Jupiter's Orbit

DU’s Robert Stencel says Jupiter is important to the history of our solar system

Juno Probe Rendering

Five years, 1.8 billion miles and $1.1 billion later, NASA’s Juno space probe is finally orbiting Jupiter – the oldest and largest planet in our solar system. NASA confirmed Juno’s arrival – 540 million miles away – after receiving a message from the space probe that read “Welcome to Jupiter!”

Juno, which is the first spacecraft to orbit Jupiter since Galileo, will do so until February 2018, during which time it will orbit Jupiter’s poles collecting data to help us better understand the complexities and realties of the planet. Juno’s July 4 arrival comes at a crucial time for space exploration given the fact that its journey is the last one NASA has scheduled – at least for now.

“As some have pointed out, this is the last major mission that’s actually in the plan. After Juno, there’s nothing in planetary science that’s very explicitly scheduled,” says Dr. Robert Stencel, the William Herschel Womble professor of astronomy at the University of Denver. “It’s kind of a make-or-break situation; we need to get some good science while we can under very challenging conditions.”

"If it turns out Jupiter is denser than lead, that would be a surprise. If it turns out Jupiter is the consistency of a Hostess Twinkie cake, that would be a surprise.” Prof. Robert Stencel, Department of Physics and Astronomy

According to Stencel, this particular mission was designed to get the “biggest bang for the buck.” He says there are three major goals for going back to Jupiter: Finding out how big Jupiter’s central core mass actually is, determining the nature of water in the atmosphere and learning more about the very large radiation fields.

“If we find out the planet doesn’t have the density theorists tell us it does, that would be a surprise and would affect the whole theory of how planets form in the first place,” Stencel says. “Jupiter, being the biggest planet in the solar system, that’s got to be telling us the story of the history of the solar system itself. If it turns out Jupiter is denser than lead, that would be a surprise. If it turns out Jupiter is the consistency of a Hostess Twinkie cake, that would be a surprise.”

The plan for Juno is to orbit close to the poles so that NASA can get a good measurement of the density structure. That measurement, however, will take some time to gather. Stencel points out that these things won’t happen overnight, as Juno will go through 53-day cycles (days close and far from the planet) during its orbit, which helps minimize the radiation damage from the planet. The first 53 days will be devoted to instrument testing to ensure the probe is functioning properly.