Astronomers analyzed images of giant hexagonal vortex on Saturn made interplanetary station “Cassini”, and found on him a system of several layers of haze. Understanding their nature and properties will allow to study the connection between the hexagon and the upper atmosphere of a gas giant. Article published in the journal Nature.
A giant hexagon on the North pole of Saturn, is unique to planets in the Solar system stable atmospheric education. It was first discovered by probes programs Voyager in 1981, and since 1991 for vortex keeps the space telescope “Hubble”. In the period from 2006 to 2017 it studied interplanetary station “Cassini”: the station has been able to see the change of seasons in the hexagon and to record his detailed images.
Cassini data also show that the hexagon is observed in the upper troposphere and stratosphere, extending more than 300 kilometers above the main cloud layers. Evaluation of the lifetime of the vortex is today more than 38 years: more than a year on Saturn (29.4 per earth year).
Astronomers led by Agustin Sanchez-Lavega (Agustín Sánchez-Lavega) from the University of the Basque Country has analyzed the images of the hexagon obtained by the station “Cassini” in June 2015. These images of high spatial resolution (1-2 km per pixel), and they cover a wide range of wavelengths (from 225 to 950 nanometers). In addition, the researchers used data from observations of Saturn space telescope the Hubble space telescope, obtained at the end of June 2015.
The photographs astronomers have discovered a system of six or seven successive layers of haze: they are located above the upper layer of clouds to the South of the hexagon. The vertical thickness of the individual layers ranged from 7 to 18 kilometers, the entire system stretched across altitudes from approximately 130 to 340 km from the visible cloud layer.
To determine the parameters of each haze, scientists have built a model in which their optical properties are described by a density of particles, their size and height, and then compared the results with observations. For the tropospheric haze the size of individual particles was equal to 1.45 micrometers, and the density was 100 particles per cubic centimeter. For stratospheric hazes the size of the individual particles amounted to 0.07 micrometer and a density of 100–500 particles per cubic centimeter.
It is assumed that the haze consists of particles of condensed hydrocarbons, such as acetylene, propan, propane, or butane diacetylene, which are formed at high altitudes by photochemical reactions. However, we cannot exclude the particles of tolinou or other products of complex chemical reactions in the atmosphere of Saturn. Vertical distribution of smoke may be due to moving up of internal gravity waves. In the future, scientists intend to investigate the mechanisms of the collapse the smoke and change their properties in connection with the change of seasons on Saturn.
Earlier we talked about how Saturn bypassed Jupiter’s satellites, as Cassini saw the auroras of Saturn in detail and why helium rain has blamed the “youth” of Saturn.