Astronomers first presented the results of a study of Jupiter by the most modern millimeter-wave observatory ALMA. The observations were carried out a few days after a flash on the surface seen in the optical range. Due to the longer wavelength, ALMA was able to study the motion of matter under the clouds and confirm the theory of the formation of such processes.
The atmosphere of Jupiter is mainly composed of hydrogen and helium, but it also contains ammonia, methane, hydrogen sulfide and water. The uppermost layer of clouds consists of ammonia ice and is divided into whitish and brownish bands visible in the optical range. Unlike the Earth, which has a hard surface close to the clouds, the atmosphere on Jupiter is very thick, and the clouds continue to great depths. Under the first layer there are clouds of solid particles of ammonium hydrosulfide NH4HS, and even deeper, at about 80 kilometers, there are clouds of liquid water droplets.
Storms in the clouds can cause distortions in surface currents and even change their color. One of these events occurred in the early days of 2017 and was noticed by amateur astronomers. Scientists decided to take this opportunity and used ground-based optical and radio telescopes to comprehensively study the storm, which looked like a bright stream above the clouds of frozen ammonia. A week later, other observatories joined them, including the Hubble Space Telescope.
The presented results of processing observations confirm the theory that jets occur at great depths under the clouds, and water plays an important role in this process. Up these jets rise up to the tropopause – the coldest part of the atmosphere. Here they expand and become partly similar to cumulonimbus clouds on Earth.
The data obtained by ALMA were in agreement with the theory of formation of jets by wet convection. According to this idea, water vapor and ammonia rise from the bowels to depths of the order of 80 kilometers under the clouds through convection, that is, upward flows of matter. In these layers, suitable conditions are formed for the condensation of steam into water droplets, which leads to the release of heat and the subsequent expansion of the flow, which begins to rise rapidly through the other layers.
Overcooled ammonia appears in the stream, which breaks through the upper layer of ammonia clouds and appears above them. In the end, it also freezes, forming a bright white stream over the colorful stripes of Jupiter. ALMA observations allowed us to obtain three-dimensional maps of the distribution of ammonia under clouds, which for the first time confirmed the theory of wet convection at a key depth.
Astronomers previously explained the swelling of the core of Jupiter by a head-on collision with the germ of the planet and found a water cloud on it. Also recently, an amateur filmed the fall of an asteroid on a giant planet.