For the first time, we have conclusive proof that the atmosphere of Jupiter’s largest moon, Ganymede, contains water vapor. It’s possible that the ice on Ganymede’s surface sublimated, going straight from a solid to a gas without melting.
The surface of Ganymede is a mix of dark, cratered regions and bright grooved terrain that produces fascinating patterns. Researchers have long thought that Ganymede has a large amount of water — possibly more than the Earth — but because Ganymede is so far from the Sun, water could only remain liquid behind a thick covering of ice.
Ganymede is assumed to have three primary layers: a metallic iron core, a rocky mantle, and a liquid and frozen layer of water. The ice shell on the outer is extraordinarily thick (around 500 miles / 800 kilometres), and any liquid water might exist beneath it. Regardless, there is water — and where there is water, there may be life.
For the first time, researchers have discovered non-ice water on the surface.
As part of a larger observation program, Lorenz Roth of the KTH Royal Institute of Technology in Stockholm, Sweden was using Hubble to measure the amount of oxygen on Ganymede. Roth and his colleagues used data from two instruments: Hubble’s Cosmic Origins Spectrograph in 2018 and archival images from the Space Telescope Imaging Spectrograph (STIS) from 1998 to 2010.
In 1998, Hubble’s Space Telescope Imaging Spectrograph (STIS) took the first ultraviolet (UV) images of Ganymede, which revealed a particular pattern in the observed emissions from the moon’s atmosphere. The moon displays auroral bands that are somewhat similar to aurora ovals observed on Earth and other planets with magnetic fields. This was illustrative evidence for the fact that Ganymede has a permanent magnetic field. The similarities in the ultraviolet observations were explained by the presence of molecular oxygen (O2). The differences were explained at the time by the presence of atomic oxygen (O), which produces a signal that affects one UV color more than the other. Credit: NASA, ESA, Lorenz Roth (KTH
Source: sci-nature.vip
