Juno launched on Aug. 5, 2011, entering Jupiter’s orbit on July 4, 2016. The findings from the first data-collection pass, which flew within about 2,600 miles (4,200 kilometers) of Jupiter's swirling cloud tops on Aug. 27, are being published this week in two papers in the journal Science, as well as 44 papers in Geophysical Research Letters.
Among the findings that challenge assumptions are those provided by Juno’s imager, JunoCam. The images show both of Jupiter's poles are covered in Earth-sized swirling storms that are densely clustered and rubbing together.
This image shows Jupiter’s south pole, as seen by NASA’s Juno spacecraft from an altitude of 32,000 miles (52,000 kilometers). The oval features are cyclones, up to 600 miles (1,000 kilometers) in diameter. Multiple images taken with the JunoCam instrument on three separate orbits were combined to show all areas in daylight, enhanced color, and stereographic projection. Credits: NASA/JPL-Caltech/SwRI/MSSS/Betsy Asher Hall/Gervasio Robles
“We're puzzled as to how they could be formed, how stable the configuration is, and why Jupiter’s north pole doesn't look like the south pole” - said Bolton.
“We're questioning whether this is a dynamic system, and are we seeing just one stage, and over the next year, we're going to watch it disappear, or is this a stable configuration and these storms are circulating around one another?”
Another surprise comes from Juno’s Microwave Radiometer (MWR), which samples the thermal microwave radiation from Jupiter’s atmosphere, from the top of the ammonia clouds to deep within its atmosphere. The MWR data indicates that Jupiter’s iconic belts and zones are mysterious, with the belt near the equator penetrating all the way down, while the belts and zones at other latitudes seem to evolve to other structures. The data suggest the ammonia is quite variable and continues to increase as far down as we can see with MWR, which is a few hundred miles or kilometers.
Juno revealed that Jupiter's magnetic field is 10 times stronger than the strongest magnetic field on Earth and and twice as strong as anticipated, exceeding researchers' expectations. The mission had an encounter with the planet's "bow shock," akin to a type of stationary shockwave, when exploring Jupiter's magnetosphere.
Even though Jupiter is the largest planet in our solar system, astronomers don't know much about its origin. The Juno mission was designed to collect data and observations that will reveal the origin and evolution of the gas giant. Its other objectives include mapping Jupiter's gravitational and magnetic fields, observing auroras, measuring the amount of water and ammonia in its atmosphere and finding evidence of a solid core.
This sequence of enhanced-color images shows how quickly the viewing geometry changes for NASA’s Juno spacecraft as it swoops by Jupiter.
“Every 53 days, we go screaming by Jupiter, get doused by a fire hose of Jovian science, and there is always something new” - said Bolton.
“On our next flyby on July 11, we will fly directly over one of the most iconic features in the entire solar system -- one that every school kid knows -- Jupiter’s Great Red Spot. If anybody is going to get to the bottom of what is going on below those mammoth swirling crimson cloud tops, it’s Juno and her cloud-piercing science instruments.”