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Great Red Spot's roots

Juno, the Nasa spacecraft that hosts two Italian instruments, unveils new details on the well-known Jupiter's storm. The findings announced at the American Geophysical Union meeting.

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.

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 300 kilometers into the planet's atmosphere. The science instrument responsible for this in-depth revelation was Juno's Microwave Radiometer (MWR). 

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 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. 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. 


Juno spacecraft (Credits: Nasa)

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 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 launched on Aug. 5, 2011, from Cape Canaveral, Florida, and arrived in orbit around Jupiter on July 5, 2016. During its mission of exploration, Juno soars low over the planet's cloud tops -- as close as about 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

JUNO's heart is the Italian JIRAM (Jovian InfraRed Auroral Mapper), financed by ASI, built by Leonardo and operated under the scientific responsibility of INAF's Institute of Astrophysics and Planetology (IAPS).  JUNO's other Italian component is KaT (Ka-Band Translator), a radio science instrument designed by 'La Sapienza' University of Rome, built by Thales Alenia Space Italia again with ASI's support.