For the first time, the Hubble Space Laboratory has detected traces of water vapor in the atmosphere of Ganymede, the largest moon of Jupiter.
Thanks to this discovery, scientists hope to determine how the atmosphere formed on Jupiter’s moon.
It is believed that the rarefied atmosphere of Ganymede arose as a result of the continuous evaporation of ice on its surface under the influence of sunlight and charged particles. However, observations showed that oxygen was in its atmosphere, but water was not detected there.
It is noteworthy that in 1998 the Hubble Space Laboratory discovered a large amount of oxygen ions in the leached atmosphere of Ganymede. At the time, scientists assumed that its source was water molecules that appear as a result of the effect of sunlight on the Ganymede ice sheet. Subsequent observations, however, showed no trace of water in the presence of oxygen.
Astronomers headed by Kurt Rosenford of the Southwest Institute for Scientific Research analyzed observations made by Hubble in April 2018, when Ganymede fell for hours in Jupiter’s shadow. Scientists compared the photographs to those taken by “Hubble” in previous years, and they were able to detect water lines in the Ganymede spectrum.
Then the scientists assessed the density of water in its atmosphere and measured its approximate mass.
Moreover, the scientists discovered that the density of water on the solar and dark sides varies greatly, and it was found that the density of water reached 30 nanograms per square meter on the surface of the solar side of Jupiter’s moon. As for its dark side, there is practically no water in it.
Rosenford and his colleagues hope that the European JUICE probe, which will be sent to Ganymede in June, will shed light on why.