NASA issues ‘Jupiter mystery’ update
Data collected by the space agency’s Juno spacecraft has shed light on a 25-year-old planetary mystery.
In 1995, NASA sent the first Galileo probe into Jupiter’s atmosphere, collecting 57 minutes, 36 seconds of data, which found that the atmosphere was much denser and hotter than scientists had expected.
New data from NASA's Juno spacecraft, revealed during the American Geophysical Union's fall conference on 11 December, now suggests that these "hot spots" are much wider and deeper than first discovered.
"Giant planets have deep atmospheres without a solid or liquid base like Earth," Scott Bolton, principal investigator of Juno at the Southwest Research Institute in San Antonio, said.
"To better understand what is happening deep into one of these worlds, you need to look below the cloud layer. Juno, which recently completed its 29th close-up science pass of Jupiter, does just that.
“The spacecraft's observations are shedding light on old mysteries and posing new questions - not only about Jupiter, but about all gas giant worlds."
During the initial probe, a “dry and windy” Jupiter atmosphere was reported, prompting scientists to attribute the findings to the 34-kilogram descent within one of the planet’s relatively rare hot spots — localised atmospheric "deserts" that traverse the gas giant's northern equatorial region.
However, results from Juno's microwave instrument indicate that the entire northern equatorial belt — a broad, brown, cyclonic band that wraps around the planet just above of the gas giant's equator — is generally a very dry region.
According to NASA, this implies that the hot spots may not be isolated "deserts”, but could be windows into a “vast region” in Jupiter's atmosphere that may be “hotter and drier than other areas”.
Juno's high-resolution data found that the Jovian hot spots are associated with breaks in the planet's cloud deck, providing a glimpse into Jupiter's deep atmosphere.
The data also found that the hot spots, flanked by clouds and active storms, are fuelling high-altitude electrical discharges, recently discovered by Juno and known as "shallow lightning” — discharges that occur in the cold upper reaches of Jupiter's atmosphere when ammonia mixes with water
"High up in the atmosphere, where shallow lightning is seen, water and ammonia are combined and become invisible to Juno's microwave instrument. This is where a special kind of hailstone that we call 'mushballs' are forming," Tristan Guillot, a Juno co-investigator at the Université Côte d'Azur in Nice, France, said.
"These mushballs get heavy and fall deep into the atmosphere, creating a large region that is depleted of both ammonia and water.
“Once the mushballs melt and evaporate, the ammonia and water change back to a gaseous state and are visible to Juno again."
Last year the Juno team reported on the cyclones of the south pole, with the Jovian Infrared Auroral Mapper instrument capturing images of a new cyclone appearing to attempt to join the five established cyclones revolving around the massive central cyclone at the south pole.
"That sixth cyclone, the baby of the group, appeared to be changing the geometric configuration at the pole - from a pentagon to a hexagon," Bolton added.
"But, alas, the attempt failed; the baby cyclone got kicked out, moved away, and eventually disappeared."
The team is yet to develop a theory regarding how these giant polar vortices form, or why some appear stable while others are born, grow, and then die relatively quickly.
The Juno team has continued to work on atmospheric models, but no model has been found to explain the phenomenon.
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