NASA's Hubble finds evidence of water vapour at Jupiter's Ganymede, solar system's largest moon

The latest findings by NASA's Hubble Space Telescope showed the first evidence of water vapour in the atmosphere of Jupiter's moon, Ganymede.

The water vapor forms when ice from the moon's surface turns from solid to gas, a process that is called sublimation. According to NASA, scientists found that water vapour exists in the atmosphere of Ganymede, the largest moon in the solar system, using a combination of new and archival observations from Hubble.

According to previous studies, it was concluded that Ganymede contains more water than all of Earth's oceans, even though the moon is 2.4 smaller than our planet. But, as the temperature in Ganymede remains extremely cold, studies had said the water on the surface may be frozen.

Scientists had speculated that the liquid ocean may "would reside roughly 100 miles below the crust; therefore, the water vapor would not represent the evaporation of this ocean."

The evidence of water vapour in the solar system's largest moon was found after astronomers re-examined Hubble's observations from the last two decades. A study on the findings was published on Monday in the journal Nature Astronomy. The new findings are crucial in the quest for extraterrestrial life and habitable worlds.

Ganymede is also the only moon in the solar system to have a magnetic field, which was first discovered in 1998 when Hubble's Space Telescope Imaging Spectrograph took the first ultraviolet (UV) images, revealing colorful ribbons of electrified gas called auroral bands. 

Researchers studied the emission and noted that Ganymede has a permanent magnetic field and the presence of molecular oxygen. 

The team, Lorenz Roth of the KTH Royal Institute of Technology in Stockholm, Sweden, studied 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.

The findings contradicted original data from 1998 and it was discovered that there was hardly any atomic oxygen in Ganymede's atmosphere.

“Initially, only the molecular oxygen had been observed... 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," Lorenz Roth said in a release.

The findings add anticipation to the European Space Agency's upcoming mission, JUICE, which will launch next year and arrive at Jupiter in 2029. JUICE observe Jupiter and its three largest moons over the course of three years