10 Things: Two Years of Juno at Jupiter

NASA’s Juno mission arrived at the King of Planets in July 2016. The intrepid robotic explorer has been revealing Jupiter's secrets ever since. Here are 10 historic Juno mission highlights.

After an odyssey of almost five years and 1.7 billion miles (2.7 billion kilometers), NASA’s Juno spacecraft fired its main engine to enter orbit around Jupiter on July 4, 2016. Juno, with its suite of nine science instruments, was the first spacecraft to orbit the giant planet since the Galileo mission in the 1990s. It would be the first mission to make repeated excursions close to the cloud tops, deep inside the planet’s powerful radiation belts.

Juno carries a color camera called JunoCam. In a remarkable first for a deep space mission, the Juno team reached out to the general public not only to help plan which pictures JunoCam would take, but also to process and enhance the resulting visual data. The results include some of the most beautiful images in the history of space exploration.

It didn’t take long for Juno—and the science teams who hungrily consumed the data it sent home—to turn theories about how Jupiter works inside out. Among the early findings: Jupiter's poles are covered in Earth-sized swirling storms that are densely clustered and rubbing together. Jupiter's iconic belts and zones were surprising, with the belt near the equator penetrating far beneath the clouds, and the belts and zones at other latitudes seeming to evolve to other structures below the surface.

The Goldstone Apple Valley Radio Telescope (GAVRT) project, a collaboration among NASA, JPL, and the Lewis Center for Educational Research, lets students do real science with a large radio telescope. GAVRT data includes Jupiter observations relevant to Juno, and Juno scientists collaborate with the students and their teachers.

Measuring in at 10,159 miles (16,350 kilometers) in width (as of April 3, 2017) Jupiter's Great Red Spot is 1.3 times as wide as Earth. The storm has been monitored since 1830 and has possibly existed for more than 350 years. In modern times, the Great Red Spot has appeared to be shrinking. In July 2017, Juno passed directly over the spot, and JunoCam images revealed a tangle of dark, veinous clouds weaving their way through a massive crimson oval.

“For hundreds of years scientists have been observing, wondering and theorizing about Jupiter’s Great Red Spot,” said Scott Bolton, Juno principal investigator from the Southwest Research Institute in San Antonio. “Now we have the best pictures ever of this iconic storm. It will take us some time to analyze all the data from not only JunoCam, but Juno’s eight science instruments, to shed some new light on the past, present and future of the Great Red Spot.”

Data collected by the Juno spacecraft during its first pass over Jupiter's Great Red Spot in July 2017 indicate that this iconic feature penetrates well below the clouds. The solar system's most famous storm appears to have roots that penetrate about 200 miles (300 kilometers) into the planet's atmosphere.

Scientists on the Juno mission observed massive amounts of energy swirling over Jupiter’s polar regions that contribute to the giant planet’s powerful auroras – only not in ways the researchers expected. Examining data collected by the ultraviolet spectrograph and energetic-particle detector instruments aboard Juno, scientists observed signatures of powerful electric potentials, aligned with Jupiter’s magnetic field, that accelerate electrons toward the Jovian atmosphere at energies up to 400,000 electron volts. This is 10 to 30 times higher than the largest such auroral potentials observed at Earth. Jupiter has the most powerful auroras in the solar system, so the team was not surprised that electric potentials play a role in their generation. What puzzled the researchers is that despite the magnitudes of these potentials at Jupiter, they are observed only sometimes and are not the source of the most intense auroras, as they are at Earth.

Juno scientists shared a 3D infrared movie depicting densely packed cyclones and anticyclones that permeate the planet’s polar regions, and the first detailed view of a dynamo, or engine, powering the magnetic field for any planet beyond Earth. Juno mission scientists took data collected by the spacecraft’s Jovian InfraRed Auroral Mapper (JIRAM) instrument and generated a 3D fly-around of the Jovian world’s north pole. Imaging in the infrared part of the spectrum, JIRAM captures light emerging from deep inside Jupiter equally well, night or day. The instrument probes the weather layer down to 30 to 45 miles (50 to 70 kilometers) below Jupiter's cloud tops.

Powerful bolts of lightning light up Jupiter’s clouds. In some ways its lightning is just like what we’re used to on Earth. In other ways, it’s very different. For example, most of Earth’s lightning strikes near the equator; on Jupiter, it’s mostly around the poles.

In June, NASA approved an update to Juno’s science operations until July 2021. This provides for an additional 41 months in orbit around. Juno is in 53-day orbits rather than 14-day orbits as initially planned because of a concern about valves on the spacecraft’s fuel system. This longer orbit means that it will take more time to collect the needed science data, but an independent panel of experts confirmed that Juno is on track to achieve its science objectives and is already returning spectacular results. The spacecraft and all its instruments are healthy and operating nominally.