New information on Europa plumes from the old Galileo mission data

Illustration of Jupiter, Europa, magnetic field lines and the Galileo space probe (Image NASA/JPL-Caltech/Univ. of Michigan)
Illustration of Jupiter, Europa, magnetic field lines and the Galileo space probe (Image NASA/JPL-Caltech/Univ. of Michigan)

An article published in the journal “Nature Astronomy” describes a new examination of data about Europa, one of the great moons of Jupiter, collected in 1997 by NASA’s Galileo space probe. A team of researchers used new computer models to interpret an anomaly in the magnetic field around Europa that had remained unexplained. The result of the new examination is that the anomaly was generated by plumes of water vapor containing various compounds, a new proof of their existence.

The mission of the Galileo space probe was the one that brought the first real clues of the presence of an ocean of liquid water under Europa’s frozen crust. Studies on this moon increased but in the last decade another underground ocean was discovered under the crust of Enceladus – one of the moons of Saturn – a sort of smaller version of Europa. The Cassini space probe’s Enceladus flybys also allowed to detect plumes of water vapor containing various compounds, a proof not only of the presence of an ocean but also of enough thermal energy to create geysers.

In the case of Europa, interesting clues arrived a few years ago from the examination of observations made with the Hubble Space Telescope, published in 2013. These are very interesting but still not conclusive clues but now even more interesting ones obtained by reviewing data collected in 1997 were presented.

Xianzhe Jia of the University of Michigan, who led the new research, found inspiration in a presentation by Melissa McGrath of the SETI Institute that included observations made with the Hubble Space Telescope. One of the areas mentioned triggered in Jia the memory of a flyby accomplished by the Galileo space probe, the closest to Europa at 200 kilometers (124 miles) of altitude.

The data collected by Galileo’s magnetometer contained something strange and the Cassini mission experience on Enceladus flybys was useful because the plumes coming out of Saturn’s moon contain materials that are ionized and leave a trace in the surrounding magnetic field. Among the Galileo instruments there was the Plasma Wave Spectrometer which was used to measure traces of plasma waves caused by charged particles and the analysis of data collected over Europa suggested the presence of plumes.

The comparison with the Hubble space telescope’s observations indicates the same location for the plumes, independent evidence collected with very different instruments that offer important confirmations to the existence of those geysers. The location is in a region of Europa where temperatures are abnormal due to the heat that comes from inside that moon.

Xianzhe Jia is also one of the investigators of two instruments of NASA’s Europa Clipper, the mission that in the coming years will go to explore Jupiter’s moon to try to understand if its ocean contains life forms. The possibility of taking samples of the plumes’ emissions would certainly add a lot of important data to better understand what chemical reactions are occurring in that ocean.

After the recent case of Ganymede, the data collected by the Galileo space probe proved useful after several years concerning Europa as well. This is yet another proof that accumulating data from various missions can be very useful even after a long time.

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