An international team of astronomers has managed to peer deep into the Jovian atmosphere using the Atacama Large Millimeter/submillimeter Array (ALMA) and several space- and ground-based optical and radio telescopes.
Spherical ALMA map of Jupiter showing the distribution of ammonia gas below Jupiter’s cloud deck. Image credit: ALMA / ESO / NAOJ / NRAO / I. de Pater et al / AUI / NSF / S. Dagnello.
“ALMA enabled us to make a 3D map of the distribution of ammonia gas below the clouds,” said Dr. Imke de Pater, a researcher with the University of California, Berkeley.
“And for the first time, we were able to study the atmosphere below the ammonia cloud layers after an energetic eruption on Jupiter.”
The Jovian atmosphere is made out of mostly hydrogen and helium, together with trace gases of methane, ammonia, hydrogen sulfide and water. The top-most cloud layer is made up of ammonia ice.
Below that is a layer of solid ammonium hydrosulfide particles, and deeper still, around 50 miles (80 km) below the upper cloud deck, there likely is a cloud layer of liquid water.
Variations in the upper clouds form the distinctive brown belts and white zones seen from Earth.
Many of the storms on Jupiter take place inside those belts. They can be compared to thunderstorms on Earth and are often associated with lightning events.
Storms reveal themselves in visible light as small bright clouds, referred to as plumes. These plume eruptions can cause a major disruption of the belt, which can be visible for months or years.
Flat map of Jupiter in radio waves from ALMA (top) and visible light from Hubble (bottom). The eruption in the South Equatorial Belt is visible in both images. Image credit: ALMA / ESO / NAOJ / NRAO / I. de Pater et al / AUI / NSF / S. Dagnello / NASA / ESA / Hubble.
The radio wave images were taken by ALMA a few days after amateur astronomers observed an eruption in Jupiter’s South Equatorial Belt in January 2017.
A small bright white plume was visible first and then a large-scale disruption in the belt was observed that lasted for weeks after the eruption.
Dr. de Pater and colleagues used ALMA to study the Jovian atmosphere below the plume and the disrupted belt at radio wavelengths.
They also compared ALMA images with UV-visible light and infrared images made with other telescopes at approximately the same time.
“Our ALMA observations are the first to show that high concentrations of ammonia gas are brought up during an energetic eruption,” Dr. de Pater said.
“The combination of observations simultaneously at many different wavelengths enabled us to examine the eruption in detail.”
“This led us to confirm the current theory that energetic plumes are triggered by moist convection at the base of water clouds, which are located deep in the atmosphere. The plumes bring up ammonia gas from deep in the atmosphere to high altitudes, well above the main ammonia cloud deck.”
“These ALMA maps at millimeter wavelengths complement the maps made with NSF’s Very Large Array in centimeter wavelengths,” said Dr. Bryan Butler, an astronomer at the National Radio Astronomy Observatory.
“Both maps probe below the cloud layers seen at optical wavelengths, and show ammonia-rich gases rising into and forming the upper cloud layers (zones), and ammonia-poor air sinking down (belts).”
A paper describing the results will be published in the Astronomical Journal.
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Imke de Pater et al. 2019. First ALMA Millimeter Wavelength Maps of Jupiter, with a Multi-Wavelength Study of Convection. AJ, in press; arXiv: 1907.11820
