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NASA’s Juno Probes the Depths of Jupiter’s Great Red Spot

New Radiation Zones on Jupiter

This graphic shows a new radiation zone surrounding Jupiter, located just above the atmosphere near the equator, that has been discovered by NASA’s Juno mission. The new radiation zone is depicted here as a glowing blue area around the planet’s middle.

This radiation zone includes energetic hydrogen, oxygen and sulfur ions moving at close to the speed of light (referred to as “relativistic” speeds). It resides inside Jupiter’s previously known radiation belts. The zone was identified by the mission’s Jupiter Energetic Particle Detector Instrument (JEDI), enabled by Juno’s unique close approach to the planet during the spacecraft’s science flybys (2,100 miles or 3,400 kilometers from the cloud tops).

Juno scientists believe the particles creating this region of intense radiation are derived from energetic neutral atoms — that is, fast-moving atoms without an electric charge — coming from the tenuous gas around Jupiter’s moons Io and Europa. The neutral atoms then become ions — atoms with an electric charge — as their electrons are stripped away by interaction with the planet’s upper atmosphere. (This discovery is discussed further in an issue of the journal Geophysical Research Letters [Kollmann et al. (2017), Geophys. Res. Lett., 44, 5259-5268].)

Juno also has detected signatures of a population of high-energy, heavy ions in the inner edges of Jupiter’s relativistic electron radiation belt. This radiation belt was previously understood to contain mostly electrons moving at near light speed. The signatures of the heavy ions are observed at high latitude locations within the electron belt — a region not previously explored by spacecraft. The origin and exact species of these heavy ions is not yet understood. Juno’s Stellar Reference Unit (SRU-1) star camera detects the signatures of this population as extremely high noise in images collected as part of the mission’s radiation monitoring investigation. The locations where the heavy ions were detected are indicated on the graphic by two bright, glowing spots along Juno’s flight path past the planet, which is shown as a white line. The invisible lines of Jupiter’s magnetic field are also portrayed here for context as faint, bluish lines.

Credits: NASA/JPL-Caltech/SwRI/JHUAPL

 

NASA’s Juno Probes the Depths of Jupiter’s Great Red Spot

Data collected by NASA’s 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. Other revelations from the mission include that Jupiter has two previously uncharted radiation zones. The findings were announced Monday at the annual American Geophysical Union meeting in New Orleans.

“One of the most basic questions about Jupiter’s Great Red Spot is: how deep are the roots?” said Scott Bolton, Juno’s principal investigator from the Southwest Research Institute in San Antonio. “Juno data indicate that the solar system’s most famous storm is almost one-and-a-half Earths wide, and has roots that penetrate about 200 miles (300 kilometers) into the planet’s atmosphere.”

The science instrument responsible for this in-depth revelation was Juno’s Microwave Radiometer (MWR). “Juno’s Microwave Radiometer has the unique capability to peer deep below Jupiter’s clouds,” said Michael Janssen, Juno co-investigator from NASA’s Jet Propulsion Laboratory in Pasadena, California. “It is proving to be an excellent instrument to help us get to the bottom of what makes the Great Red Spot so great.”

Slices of Jupiter’s Great Red Spot

This figure shows data from the six channels of the microwave radiometer (MWR) instrument onboard NASA’s Juno spacecraft. The data were collected in the mission’s sixth science orbit (referred to as “perijove 7”), during which the spacecraft passed over Jupiter’s Great Red Spot. The top layer in the figure is a visible light image from the mission’s JunoCam instrument, provided for context.

The MWR instrument enables Juno to see deeper into Jupiter than any previous spacecraft or Earth-based observations. Each MWR channel peers progressively deeper below the visible cloud tops. Channel 1 is sensitive to longer microwave wavelengths; each of the other channels is sensitive to progressively shorter wavelengths.

The large-scale structure of the Great Red Spot is visible in the data as deep into Jupiter as MWR can observe.

Credits: NASA/JPL-Caltech/SwRI

 

Jupiter’s Great Red Spot is a giant oval of crimson-colored clouds in Jupiter’s southern hemisphere that race counterclockwise around the oval’s perimeter with wind speeds greater than any storm on Earth. Measuring 10,000 miles (16,000 kilometers) in width as of April 3, 2017, the Great Red Spot is 1.3 times as wide as Earth.

“Juno found that the Great Red Spot’s roots go 50 to 100 times deeper than Earth’s oceans and are warmer at the base than they are at the top,” said Andy Ingersoll, professor of planetary science at Caltech and a Juno co-investigator. “Winds are associated with differences in temperature, and the warmth of the spot’s base explains the ferocious winds we see at the top of the atmosphere.”

The future of the Great Red Spot is still very much up for debate. While the storm has been monitored since 1830, it has possibly existed for more than 350 years. In the 19th century, the Great Red Spot was well over two Earths wide. But in modern times, the Great Red Spot appears to be diminishing in size, as measured by Earth-based telescopes and spacecraft. At the time NASA’s Voyagers 1 and 2 sped by Jupiter on their way to Saturn and beyond, in 1979, the Great Red Spot was twice Earth’s diameter. Today, measurements by Earth-based telescopes indicate the oval that Juno flew over has diminished in width by one-third and height by one-eighth since Voyager times.

Juno also has detected a new radiation zone, just above the gas giant’s atmosphere, near the equator. The zone includes energetic hydrogen, oxygen and sulfur ions moving at almost light speed.

“The closer you get to Jupiter, the weirder it gets,” said Heidi Becker, Juno’s radiation monitoring investigation lead at JPL. “We knew the radiation would probably surprise us, but we didn’t think we’d find a new radiation zone that close to the planet. We only found it because Juno’s unique orbit around Jupiter allows it to get really close to the cloud tops during science collection flybys, and we literally flew through it.”

Great Red Spot Rotation (animation)

Winds around Jupiter’s Great Red Spot are simulated in this JunoCam view that has been animated using a model of the winds there. The wind model, called a velocity field, was derived from data collected by NASA’s Voyager spacecraft and Earth-based telescopes.

NASA’s Juno spacecraft acquired the original, static view during passage over the spot on July 10, 2017. Citizen scientists Gerald Eichstädt and Justin Cowart turned the JunoCam data into a color image mosaic. Juno scientists Shawn Ewald and Andrew Ingersoll applied the velocity data to the image to produce a looping animation.

Credits: NASA/JPL-Caltech/SwRI/MSSS/Gerald Eichstadt/Justin Cowart

 

The new zone was identified by the Jupiter Energetic Particle Detector Instrument (JEDI) investigation. The particles are believed to be derived from energetic neutral atoms (fast-moving ions with no electric charge) created in the gas around the Jupiter moons Io and Europa. The neutral atoms then become ions as their electrons are stripped away by interaction with the upper atmosphere of Jupiter.

Juno also found signatures of a high-energy heavy ion population within the inner edges of Jupiter’s relativistic electron radiation belt — a region dominated by electrons moving close to the speed of light. The signatures are observed during Juno’s high-latitude encounters with the electron belt, in regions never explored by prior spacecraft. The origin and exact species of these particles is not yet understood. Juno’s Stellar Reference Unit (SRU-1) star camera detects the signatures of this population as extremely high noise signatures in images collected by the mission’s radiation monitoring investigation.

To date, Juno has completed eight science passes over Jupiter. Juno’s ninth science pass will be on Dec. 16.

Juno launched on Aug. 5, 2011, from Cape Canaveral, Florida, and arrived in orbit around Jupiter on July 4, 2016. During its mission of exploration, Juno soars low over the planet’s cloud tops — as close as about 2,100 miles (3,400 kilometers). During these flybys, Juno is probing beneath the obscuring cloud cover of Jupiter and studying its auroras to learn more about the planet’s origins, structure, atmosphere and magnetosphere.

JPL manages the Juno mission for the principal investigator, Scott Bolton, of Southwest Research Institute in San Antonio. The Juno mission is part of the New Frontiers Program managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama, for the Science Mission Directorate. Lockheed Martin Space Systems, Denver, built the spacecraft. JPL is a division of Caltech in Pasadena, California.

source: Dwayne Brown / Laurie Cantillo
NASA Headquarters, Washington

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