Behind The Black – Robert Zimmerman

Cool image time! The image on the right, reduced to post here, shows Jupiter’s south pole and much of its southern hemisphere. It was taken during Juno’s last orbital fly-by of the gas giant’s cloud tops last week, and has been enhanced by Fevig-58, an ordinary citizen who downloaded the raw image and then uploaded his enhanced version to the Juno website.

It is definitely worthwhile taking a close look at the full resolution image. At the top its shows the horizontally banded Jupiter at equatorial- and mid-latitudes that has been that planet’s familiar face for centuries. In the middle is the transitional region from those horizontal bands to the chaotic polar regions. And at the bottom is the pole, where there the storms appear to follow no pattern and form a mish-mash.

One thing about Jupiter’s pole. It appears very different than Saturn’s. While I am certain they will find a vortex of some kind there, so far there is no indication of a coherent jet stream, as seen by Saturn’s hexagon. This once again demonstrates the one unbroken rule of planetary science that has been found with every planetary mission to every planetary body, whether they be pebbles, asteroids, dwarf planets, gas giants, or moons: Every single one of them is different and unique. They might fall into a single category, say gas giants, but each has its own unique features that make it different from every other member of that category.

The Juno science team today released their first research results since the spacecraft entered orbit around Jupiter in July 2016.

“Although many of the observations have terrestrial analogs, it appears that different processes are at work creating the auroras,” said SwRI’s Dr. Phil Valek, JADE instrument lead. “With JADE we’ve observed plasmas upwelling from the upper atmosphere to help populate Jupiter’s magnetosphere. However, the energetic particles associated with Jovian auroras are very different from those that power the most intense auroral emissions at Earth.”

Also surprising, Jupiter’s signature bands disappear near its poles. JunoCam images show a chaotic scene of swirling storms up to the size of Mars towering above a bluish backdrop. Since the first observations of these belts and zones many decades ago, scientists have wondered how far beneath the gas giant’s swirling façade these features persist. Juno’s microwave sounding instrument reveals that topical weather phenomena extend deep below the cloudtops, to pressures of 100 bars, 100 times Earth’s air pressure at sea level.

“However, there’s a north-south asymmetry. The depths of the bands are distributed unequally,” Bolton said. “We’ve observed a narrow ammonia-rich plume at the equator. It resembles a deeper, wider version of the air currents that rise from Earth’s equator and generate the trade winds.”

Juno is mapping Jupiter’s gravitational and magnetic fields to better understand the planet’s interior structure and measure the mass of the core. Scientists think a dynamo — a rotating, convecting, electrically conducting fluid in a planet’s outer core — is the mechanism for generating the planetary magnetic fields. “Juno’s gravity field measurements differ significantly from what we expected, which has implications for the distribution of heavy elements in the interior, including the existence and mass of Jupiter’s core,” Bolton said. The magnitude of the observed magnetic field was 7.766 Gauss, significantly stronger than expected. But the real surprise was the dramatic spatial variation in the field, which was significantly higher than expected in some locations, and markedly lower in others. “We characterized the field to estimate the depth of the dynamo region, suggesting that it may occur in a molecular hydrogen layer above the pressure-induced transition to the metallic state.”

What I want to see is a depth map showing where Jupiter’s atmosphere ends and its solid core begins. I expect Juno will eventually be able to give us a first glimpse.