The Juno spacecraft performed its 11th close flyby of Jupiter on Feb. 7. As usual, it sent stunning images and important science data back to Earth, which will be studied for years to come.
Based on recent data from Juno, researchers have concluded that the atmospheric winds of the gas-giant planet run deep into its atmosphere, to a depth of almost 3,000 km, and last longer than similar atmospheric processes found here on Earth. The findings will improve understanding of Jupiter’s interior structure, core mass and, eventually, its origin. www.nasa.gov/...
The Depth of Jupiter's Colored Storms
The depth to which the roots of Jupiter’s famous zones and belts extend has been a mystery for decades. Juno's microwave instrument can only peer a few hundred kilometers into a planet that’s 70,000 kilometers deep. Gravity measurements collected by Juno during its close flybys of the planet have now provided an answer.
The Juno science team measured tiny variations in Jupiter’s gravitational field by looking for corresponding perturbations in Juno’s orbital velocity; these changes in velocity were detected via doppler variations in the frequency of signals arriving at Earth from Juno. The magnitude of the asymmetries in gravity across regions of Jupiter helped calculate the depth and mass of the jet streams.
Much of this data was collected in the 10th flyby. During orbits that highlight gravity experiments, Juno is in an Earth-pointed orientation that allows both the X-band and Ka-Band transmitter to downlink data in real-time to one of the antennas of NASA's Deep Space Network in Goldstone, California.
The result was a surprise for the Juno science team because it indicated that the weather layer of Jupiter was more massive, extending much deeper than previously expected. The Jovian weather layer, from its very top to a depth of 3,000 kilometers, contains about one percent of Jupiter’s mass (about 3 Earth masses).
Yohai Kaspi, who led the effort, said —
One way of interpreting this: Jupiter has an atmosphere that is 3,000 kilometers thick. Below that, Jupiter’s interior behaves more as a solid body -- it behaves like Earth does when it rotates. Its layers may be liquid in some places and solid in others, but even the liquid layers are all rotating together as a single entity.
... it’s not the concentric [differentially rotating] cylinders we were thinking about before.
See Emily Lakdawalla’s article at www.planetary.org/… for a more detailed explanation.
The animation below show these east-west jet-streams that penetrate deep into the planet's atmosphere, to a depth of about 3,000 km. Due to Jupiter's rapid rotation (Jupiter's day is about 10 hours), these flows extend into the interior parallel to Jupiter's axis of rotation. Below this layer the flows decay, possibly slowed by Jupiter's strong magnetic field.
Pepperoni Pizza?
Other Juno science results released on Mar 7 include that the massive cyclones that surround Jupiter’s north and south poles are long-lasting atmospheric features and unlike anything else encountered in our solar system.
Jupiter's north pole is dominated by a central cyclone surrounded by eight circumpolar cyclones with diameters ranging from 4,000 to 4,600 km. Jupiter's south pole also contains a central cyclone, but it is surrounded by five cyclones with diameters ranging from 5,600 to 7,000 km. Almost all the polar cyclones, at both poles, are so densely packed that their spiral arms come in contact with adjacent cyclones. Scientists are still working on understanding why they do not merge.
In contrast, based on Cassini data, Saturn has a single cyclonic vortex at each pole.
The image above is that of the North pole. Here is a computer-generated image of the south pole. Both images were generated from data collected by the Jovian Infrared Auroral Mapper (JIRAM) instrument aboard the Juno spacecraft.
Jupiter’s Twilight Zone
The beautiful image below captures the swirling cloud formations around the south pole of Jupiter.
NASA’s Juno spacecraft took the color-enhanced image during its 11th close flyby of the gas giant planet on Feb 7. At the time, the spacecraft was 120,533 km from the tops of Jupiter’s clouds at 84.9 degrees south latitude.
Citizen scientist Gerald Eichstädt processed this image using multiple photos at different exposures taken by the JunoCam imager.
The following is a mesmerizing video of Juno’s Perijove-11 Jupiter flyby on Feb 7, 2018, reconstructed by Gerald Eichstädt using JunoCam images.
Mission Future
Juno’s next close flyby of Jupiter (Perijove 12) will be on April 1. Juno is currently in a 53-day orbit and will remain in that orbit until the end of mission.
The Juno mission budget will run out in July 2018, after Perijove 14. Most likely, the mission will be extended with additional funding in the next science review cycle.
As mission end, whenever that occurs, Juno will perform a controlled de-orbit and disintegrate into Jupiter's atmosphere.
On to Europa
Although the Europa Lander mission has been shelved, the Europa Clipper orbiter mission is on track to launch around 2022 - 2025; it will study Europa through a series of flybys while in orbit around Jupiter. The spacecraft will perform 45 flybys of Europa at closest-approach altitudes varying from 25 km to 2,700 km above the surface.
Further Reading
- #AGU17: Spherical harmonics, gravity, and the depth of winds at Jupiter — www.planetary.org/…
- NASA Juno Findings - Jupiter’s Jet-Streams Are Unearthly — www.nasa.gov/…
- Gravitational signature of Jupiter’s internal dynamics — www.google.com/…
- Jupiter’s atmospheric jet streams extend thousands of kilometres deep — www.nature.com/…
- Juno's Latest Jupiter Flyby (Dec 2016) — www.dailykos.com/…
- NASA to Hold Media Call on Evidence of Surprising Activity on Europa — www.dailykos.com/...