No liquid magma ocean beneath Io's surface
Under the surface of Io, the Galilean satellite closest to Jupiter, there is not an ocean of liquid magma as had been thought until now, but a solid mantle. This was revealed in a study published in Nature, which was also carried out thanks to the work of several researchers from Sapienza University of Rome and the University of Bologna.
The research, coordinated by Ryan Park of NASA's Jet Propulsion Laboratory, exploited data collected by NASA's Juno probe during two recent close flyovers of the moon along with historical data from the Galileo mission, the NASA probe that explored the Jupiter system between 1995 and 2003.
“Combining the data acquired by Juno with those collected by the Galileo probe over 20 years ago”, says Daniele Durante, researcher at the Department of Mechanical and Aerospace Engineering, "has allowed us to improve the estimation of Io's tidal response, which gives direct indications of the deformability of the moon's internal structure”.
Io is a unique satellite in the Jovian system due to its intense volcanic activity, making it the most geologically active object in the Solar System. For decades, it was thought that Jupiter's enormous gravitational pull was sufficient to create an ocean of magma beneath its surface, feeding its volcanoes. Magnetic induction measurements taken by the Galileo probe had indeed suggested the presence of a magma ocean beneath the surface of this moon.
However, this scenario has been revised following new observations made by Juno, the probe that has been exploring Jupiter and, more recently, its moons since 2016. Juno flew over Io twice at an altitude of about 1,500 kilometres, collecting very accurate data of the moon's gravitational field. The results of the analysis show a rather modest gravitational response of the moon to tidal forces.
“The moon's response to the tidal forces exerted by Jupiter was quite low”, says Luciano Iess, professor at the Department of Mechanical and Aerospace Engineering, “an indication of the absence of a magma ocean near the surface and, rather, the presence of a deep solid mantle within it”.
The study was published in Nature under the title ‘Io's tidal response precludes a shallow magma ocean’. Participating for Sapienza University of Rome were Daniele Durante and Luciano Iess, in collaboration with colleagues from the University of Bologna, Luis Gomez Casajus, Marco Zannoni, Andrea Magnanini and Paolo Tortora. The research activities were carried out under an agreement funded by the Italian Space Agency.
References:
Park, R.S., Jacobson, R.A., Gomez Casajus, L. et al. Io’s tidal response precludes a shallow magma ocean. Nature (2024). https://doi.org/10.1038/
Further Information
Daniele Durante
Department of Mechanical and Aerospace Engineering
Luciano Iess
Department of Mechanical and Aerospace Engineering