Department of Climate and Space Sciences and Engineering in the College of Engineering at the University of Michigan


NASA Releases First Science Results from Juno Mission

Posted: May 30, 2017

NASA Releases First Science Results from Juno Mission

Last week, the Juno science team announced the first mission science results from the spacecraft’s close flyby of the gas giant. Climate Space professor Sushil Atreya is co-investigator for the mission, and shares these comments:

“Juno’s observations of Jupiter have revealed a number of phenomena that were previously unknown. My own involvement on Juno is mainly in the area of the origin and evolution of Jupiter, and the composition, chemistry and cloud physics of Jupiter’s atmosphere. To that end, data from Juno’s microwave radiometer (MWR), Jovian infrared auroral mapper, and the camera (JunoCam) are of particular interest to me. Three findings from Juno are especially striking in this regard: the distribution of ammonia, polar storms, and the infrared auroras. They all tend to indicate that the energy generated in the interior and the polar regions of Jupiter’s atmosphere must play a much bigger role in the phenomena observed on Juno than previously thought.

“The microwave radiometer, which “listens” to Jupiter’s radio emissions with six onboard antennas, shows that the distribution of ammonia is quite complex. A plume of ammonia gas appears to be rising from near the equator from deep in the interior of Jupiter. Or, looking down from the top, ammonia is depleted to well below the depths it was expected to on the basis of cloud models. That was actually known from the observations made with the Galileo probe that entered Jupiter in 1995, but with a big difference. The Galileo probe sampled only a single location of Jupiter, which also turned out to be an extremely dry spot of Jupiter, and to a pressure level of 22 bars, whereas Juno MWR is sampling pretty much the entire planet to a depth in excess of 100 bars. Contrary to Galileo probe, Juno data show the depletion in ammonia extends down to tens of bars as opposed to about 10 bars in the Galileo data, although the Galileo and Juno data agree on the relative amount of ammonia in the deep well-mixed atmosphere. The extremely deep structure in ammonia seen on Juno could only be discerned from the low frequency radio emissions measured by the MWR; no other instrument in the past had such capability. The deep structure in ammonia is an indication of complex dynamical behavior of Jupiter, perhaps driven by the heat generated in Jupiter’s interior, and controlled less by the energy from the sun, unlike the earth 

“The cyclones observed by JunoCam over both the north and south poles of Jupiter are striking in their complexity. Juno’s special orbit as the spacecraft dives from north pole to the south pole permits unprecedented look at the polar storms, never seen before by any previous spacecraft. The regular bands of belts and zones that run from equator to midlatitudes give to swirling cyclones over the poles. Perhaps both the enormous power input in the Jupiter’s polar magnetosphere, which exceeds that in the earth’s magnetosphere by a factor of 1000-10,000, and the internal heat of Jupiter play a role in driving these storms. The power in the magnetosphere is also responsible for the widespread aurora in the infrared part of the spectrum (H3+), observed by JIRAM. Complementary data from Juno’s ultraviolet spectrometer will further help constrain the auroral generation processes and the chemistry in Jupiter’s polar regions.

“Juno’s observations began only in July 2016, and cover six close passes of Jupiter (perijove) so far. In time, more and more of Jupiter’s landscape will be revealed. Those data will be crucial in understanding the dynamics, energetics and chemistry over the entire planet. The elemental abundance of nitrogen from its main reservoir, ammonia, in Jupiter provides one constraint on Jupiter’s formation and evolution models. Once Juno MWR retrieves the oxygen elemental abundance, which the Galileo probe could not do because of its dry entry site in Jupiter, another important constraint will be obtained. These data can then be combined with the set of elemental abundances on the noble gases and isotopes already known from the Galileo probe to complete the picture of how Jupiter came about and how it evolved.”

Sushil Atreya has been a co-investigator on the Juno mission since its inception in 2004. He was also on the science team of the Galileo mission, whose data are complementary to Juno’s composition data, and thus crucial for understanding Jupiter’s origin and evolution of the planet.

For more information about the Juno mission science results, visit the mission page here:

Or visit the NASA Juno Tumblr page:

For a Juno mission overview: