NASA has confirmed that researchers have discovered the first evidence of water vapor on Jupiter’s icy moon, Ganymede after researchers analyzed data taken by the Hubble Space Telescope 20 years apart.

Experts compared ultraviolet observations of Ganymede made by Hubble’s Space Telescope Imaging Spectrograph in 1998 and 2010, and compared them with 2018 observations.

STIS’ 1998 UV images showed moon atmosphere bands that looked similar to Earth’s aurora. Scientists believed that higher levels of atomic oxygen caused the discrepancy in earlier observations.

The 2018 UV observations by Hubble’s Cosmic Oscillator Spectrograph (COS) revealed that there was not much atomic oxygen found in Ganymede’s atmospheric. This could explain why the UV aurora images are so different.

Now, they believe that the temperature near Ganymede’s equator ‘becomes sufficiently warm that the icy surface releases some small amounts of water molecules,’ the European Space Agency said in a statement.


Ganymede was discovered in January 1610. Since then, it has been the subject of numerous observations, first by Earth-based telescopes and then by flyby missions and spacecraft orbiting Jupiter.

These studies show a complex icy planet whose surface is marked by the stark contrast between its two main terrain types: the darker, older, heavily cratered areas and the lighter, more recent (but still old) regions that are marked with a wide array of grooves, ridges, and smoother, less rocky regions.

Ganymede has a diameter greater than Pluto and Mercury at 3,280 miles (5 262 kilometers).

It is also the only satellite known to possess its own magnetosphere.

‘So far only the O2 had been observed,’ the study’s lead author, Lorenz Roth of the KTH Royal Institute of Technology, said in a statement released by NASA.

“This happens when charged particles are able to erode the ice surface. We have measured water vapor as a result of ice sublimation, which is caused by thermal escape of H2O from warm icy areas.

“Ganymede’s surface temperatures vary strongly throughout the day. Around noon, near the Equator, it may become sufficiently hot that water molecules can be released from the icy surface,” ESA stated in their statement.

“In fact, the UV images’ perceived differences are directly related to where water is expected to be found in the moon’s atmosphere.”

NASA and ESA have partnered to create the Hubble Space Telescope.

Roth said that the ESA’s Jupiter ICy moons Explorer mission (JUICE), will launch next year. It is expected to reach Jupiter in 2029. Roth stated that the JUICE instrument teams can use the results to improve their observation plans and optimize the use spacecraft.

Also Read: As Delta variant spreads, so do vaccine mandates

JUICE will be studying the largest planet in our solar system as part of its mission. It will also study three of its largest moons. “With particular emphasis on Ganymede, as a potential planetary body, and habitable world,” the ESA said.

The findings were published Monday in the journal Nature Astronomy.

After being discovered in January 1610 by Galileo Galilei, the largest of Jupiter’s moons (Io, Europa and Ganymede), they are now known as Galilean Moons.

Ganymede is Jupiter’s largest moon. It is also the largest moon in the solar system and the only one with its own magnetic field.