Scientists have long noticed a lack of ammonia in the atmospheres of Uranus and Neptune when compared to the amounts seen on Jupiter and Saturn. Many considered that reality odd as planetary development designs suggested that all gas giants originated from the same “prehistoric soup,” so their compositions must be similar. Theories abounded as to where the ammonia had gone, however a better evaluation of Jupiter itself mean a possible description.
Composite image of the gas giants.Credit– Jupiter from Juno: NASA/SwRI/MSSS/ Gerald Eichstädt/ Seán Doran; Saturn from Cassini: NASA/JPL-Caltech/Space Science Institute; Uranus and Neptune from HST: NASA/ESA/A. Simon (NASA Goddard Space Flight Center), and M.H. Wong and A. Hsu (University of California, Berkeley).
Juno, a probe that is currently checking out the Jupiter system, observed that ammonia in the upper environment formed “mushballs” by combining with water also present in the environment. Like hailstones, these mushballs are more liquid than conventional hailstones, as the ammonia liquefies water enters into contact with even at very low temperature levels, such as those discovered in Jupiters upper atmosphere.
These amalgamated mushballs can grow to be larger than some of the more huge hailstones on Earth. They are also prone to rapidly failing the environment, dragging their constituent parts down out of the upper reaches of the atmosphere. As they get closer to the center of Jupiter, the temperature rises, vaporizing the ammonia and water and allowing them to climb up back towards the observable upper reaches.
The ammonia mushball cycle as seen on Jupiter.Credit: NASA/ JPL– Caltech/ SwRI/ CNRS
According to Tristan Guillot of the CRNS Laboratoire Lagrange, the same procedure may be taking place on Neptune and Uranus, but the mushballs hold the ammonia down in the lower atmosphere for longer, without as much opportunity of releasing it back up to observable elevations..
At such low altitudes, the ammonia would appear to be missing out on with present observational capabilities. The upper layers of clouds would obscure any ammonia reading, making it look like if it disappeared..
One benefit to planetary science is that insights from one planet might explain phenomena on another. We understand Venus greenhouse gas effect from our own experience on the Earth, and Jupiter and Saturn share some characteristics. But Jupiter also offers insight into other, farther out systems, such as Uranus and Neptune. Now, a discovery from a spacecraft orbiting Jupiter might have solved a long-standing secret about Uranus and Neptune– where has all the ammonia gone?
UT video talking about the exploration of Uranus and Neptune.
To see the disappeared ammonia would need a dedicated mission specifically to explore the lower atmospheres of the external planets. Some missions have been touted in the past, however none are presently operational. As Dr. Guillot mentions, understanding the external worlds in our own solar system would assist us understand the environments of exoplanets far beyond our own planetary system. Maybe it is time to send out a devoted probe out to discover more about our farthest out planetary neighbors.
Learn More: EuroPlanet Society– Mushballs store missing out on ammonia at Uranus and NeptuneEarthSky– Mushballs explain missing ammonia on ice giantsAGU– Storms and the Depletion of Ammonia in Jupiter: I. Microphysics of “Mushballs” UT– Ammonia Key to Titans Atmosphere.
Lead Image: Artists representation of a mushball in a gas giants atmosphere.Credit– NASA/JPL-Caltech/SwRI/ CNRS.
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Now, a discovery from a spacecraft orbiting Jupiter might have solved a long-standing secret about Uranus and Neptune– where has all the ammonia gone?
Theories abounded as to where the ammonia had actually gone, however a more detailed evaluation of Jupiter itself tips at a possible description.
As they get closer to the center of Jupiter, the temperature level increases, vaporizing the ammonia and water and allowing them to climb up back towards the observable upper reaches.
Perhaps it is time to send a devoted probe out to discover more about our farthest out planetary neighbors.
