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Hubble finds evidence of water vapour on Jupiter’s moon Ganymede

At noon, Ganymede's surface may become warm near the equator and the icy surface may release water molecules.

This image presents an artist’s impression of Jupiter’s moon Ganymede. (ESA/Hubble, J. daSilva)

By analysing data from the NASA/ESA Hubble Space Telescope, researchers have found the first evidence of water vapour in the atmosphere of Ganymede, Jupiter’s largest moon.

Previous studies have shown that Ganymede may have more water than Earth, but as it is extremely cold (minus 100 to 180 degrees Celsius), the water on the surface may be frozen. It was speculated that the liquid ocean may lie about 160 kilometres below the surface. This new evidence for a water atmosphere on Ganymede is crucial in our search for extraterrestrial life and habitable worlds.

How did they find this?

In 1998, the Space Telescope Imaging Spectrograph (STIS) of Hubble took the first ultraviolet pictures of Ganymede. By studying the emissions, researchers noted that Ganymede has a permanent magnetic field and some atomic oxygen. In 2018, Hubble’s Cosmic Origins Spectrograph (COS) instrument was used to measure the amount of this atomic oxygen. The study team combined data from 1998, 2010 and 2018 and to their surprise noted some contrast to the original findings.

“Initially, only the O2 had been observed,” explained Lorenz Roth, of the KTH Royal Institute of Technology in Stockholm, Sweden, in a release. “This is produced when charged particles erode the ice surface. The water vapour that we have now measured originates from ice sublimation caused by the thermal escape of H2O vapour from warm icy regions.”

He is the corresponding author of the paper published yesterday in Nature Astronomy. The authors explain that at noon, Ganymede’s surface may become warm near the equator, and the icy surface may release water molecules.

JUICE mission

The European Space Agency (ESA) is gearing up for the JUpiter ICy moons Explorer (JUICE) mission and this new find adds to the excitement. The JUICE mission is to launch next year and arrive at Jupiter in 2029. It will spend three years studying the planet and three of its largest moons. “Our results can provide the JUICE instrument teams with valuable information that may be used to refine their observation plans to optimise the use of the spacecraft,” added Roth.

“Understanding the Jovian system and unravelling its history, from its origin to the possible emergence of habitable environments, will provide us with a better understanding of how gas giant planets and their satellites form and evolve. In addition, new insights will hopefully be found into the potential for the emergence of life in Jupiter-like exoplanetary systems,” added a release from ESA.

First published on: 27-07-2021 at 16:45 IST
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