2023-11-02 19:15:28
With a diameter larger than that of the planet Mercury, Ganymede is the largest of Jupiter’s moons and has long attracted great interest due to the vast internal ocean of water that, according to all indications, is hidden beneath its icy crust. Like Europa (another of Jupiter’s moons), the presence of an underground ocean of water raises the possibility of life.
Previous spectroscopic observations carried out by NASA’s Galileo space probe and the Hubble Space Telescope, as well as by the VLT (Very Large Telescope) of the European Southern Observatory (ESO), already pointed to the presence of salts and organic compounds in Ganymede, but the spatial resolution of these observations was too low to achieve unambiguous detection.
On June 7, 2021, the Juno spacecraft flew over Ganymede at a minimum altitude of just over a thousand kilometers. Shortly after the moment of closest approach, the JIRAM spectrometer obtained infrared images and infrared spectra of the surface of Ganymede. A spectrum essentially shows the chemical fingerprints left in light by different materials.
Built by the Italian Space Agency, JIRAM was designed to capture infrared light (invisible to the naked eye) emerging from the depths of Jupiter. This allows us to peer into Jupiter’s atmosphere to a depth of between 50 and 70 kilometers below the cloud tops of the gas giant planet. But the instrument has also been used to collect terrain information on the moons Io, Europa, Ganymede and Callisto (collectively known as the Galilean moons after their discoverer, Galileo).
The Ganymede data obtained by JIRAM during the flyby reached an unprecedented spatial resolution for infrared spectroscopy: approximately 1 kilometer per pixel.
The data collected was thoroughly analyzed.
This enhanced image of Ganymede was obtained by NASA’s Juno space probe during the flyby of that moon of Jupiter on June 7, 2021. The data collected during that flyby has been used to detect the presence of salts and organic compounds on Ganymede. (Photo: NASA JPL / Caltech / SwRI / MSSS / Kalleheikki Kannisto. CC BY)
The long and detailed analysis, carried out by Federico Tosi’s team, from the National Institute of Astrophysics in Rome, Italy, has revealed the presence of unequivocal spectral features of some organic compounds and certain salts.
Hydrated sodium chloride, ammonium chloride and sodium bicarbonate, among other compounds, have been detected.
What was discovered in this study could help us better understand the origin of Ganymede and the composition of its underground ocean.
Previous models of Ganymede’s magnetic field determined that the equatorial region of the star, up to a latitude of about 40 degrees, is protected from the highly energetic bombardment of electrons and heavy ions created by Jupiter’s infernal magnetic field. The presence of such particle flows is known to have negative effects on the stability and durability of salts and organic compounds.
Ganymede is not the only satellite of Jupiter that Juno has flown by. The moon Europa, which is also believed to harbor an ocean of liquid water beneath its icy crust, was flown by Juno, first in October 2021 and then in September 2022. Now it’s Io’s turn. If all goes well, Juno will fly over Io on December 30, approaching the surface of this world full of volcanoes to a minimum distance of about 1,500 kilometers.
The study is titled “Salts and organics on Ganymede’s surface observed by the JIRAM spectrometer onboard Juno”. And it has been published in the academic journal Nature Astronomy. (Source: NCYT from Amazings)
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