Juno Microwave Radiometer Observations Reveal A Warmer Polar Atmosphere on Jupiter

TL;DR

Juno Microwave Radiometer observations reveal that Jupiter's north pole is warmer than the equator at the 1-bar level, indicating possible enhanced internal heat flux and providing new insights into polar atmospheric structure.

Contribution

This study provides high-resolution microwave mapping of Jupiter's north pole, offering new constraints on atmospheric composition and internal heat distribution.

Findings

North pole is 6-7 K warmer than the equator at 1-bar level.

Deep ammonia abundance is approximately 355 ppmv, similar to lower latitudes.

Water abundance is about 1.8 times solar, consistent with previous estimates.

Abstract

The intriguing circumpolar cyclone pattern at Jupiter's poles raises fundamental questions about how these systems are organized vertically and, further, how the planet's internal heat shapes and sustains them in the absence of solar insolation. We report recent close-in observations of Jupiter's north pole acquired by NASA's Juno Microwave Radiometer (MWR), which achieved comprehensive microwave mapping of the region at an unprecedentedly high resolution. Using six-channel measurements from eleven perijove passes (PJ51-PJ61) poleward of 75N, we derive polar-mean nadir brightness temperatures and limb-darkening spectra that together point to two equally plausible atmospheric scenarios: (1) a dry-adiabatic profile with slightly depleted ammonia gas at a few bars, or (2) a moist-adiabatic profile with uniform ammonia. Markov chain Monte Carlo retrievals yield a deep ammonia abundance of 354.8+12.0/-11.0 ppmv (3+/-0.1 x solar) and a water abundance of 1.8+1.5/-1.1 x 1000 ppmv (2.1+1.8/-1.3 x solar), resembling previous estimates at lower latitudes. Remarkably, the north pole is found to be 6-7 K warmer than the equator at the 1-bar level, although the inferred difference is close to the 1-sigma uncertainty level. If confirmed, this result would suggest an enhanced internal heat flux toward the poles, which is consistent with the more intense lightning activity observed at high latitudes.