NASA's Hubble finds first evidence of water vapor on Jupiter's largest moon Ganymede

For the first time, scientists have discovered the first evidence of water vapor on Jupiter's largest moon, Ganymede. This water vapor forms when ice from the moon's surface sublimates or turns from solid to gas. Scientists have used new and archival datasets from NASA's Hubble Space Telescope to make the discovery, published in the journal Nature Astronomy. 

There were pieces of evidence retrieved from the previous research that said Ganymede, the largest moon in the solar system, contains more water than all of Earth's oceans. But, due to low temperatures, water on the surface would freeze. The water vapor would not represent the evaporation of Ganymede's ocean as it would reside roughly 100 miles below the crust. 

For the past two decades, the astronomers have re-examined Hubble's observations to find this evidence of water vapor.

The first ultraviolet (UV) images of Ganymede was taken by Hubble's Space Telescope Imaging Spectrograph in 1998, which revealed colorful ribbons of electrified gas called auroral bands and provided further evidence that Ganymede has a weak magnetic field.

NASA's Juno Mission

To support NASA's Juno mission in 2018, a team led by Lorenz Roth of the KTH Royal Institute of Technology in Stockholm, Sweden examined data captured by Hubble's Cosmic Origins Spectrograph in 2018 and images of the Space Telescope Imaging Spectrograph obtained between 1998 and 2010.

Contrary to the previous interpretations of the data from 1998, they discovered that there was hardly any atomic oxygen in Ganymede's atmosphere which means there must be another explanation for the apparent differences in these UV aurora images.

Roth explained, "So far only the molecular oxygen had been observed. This is produced when charged particles erode the ice surface. The water vapor that we measured now originates from ice sublimation caused by the thermal escape of water vapor from warm icy regions."

In a recent update, NASA's Juno mission released new imagery of the icy moon. Juno has been studying Jupiter and its environment, also known as the Jovian system, since 2016. 

Hubble Space Telescope

The Hubble Space Telescope is a large telescope in space, launched into orbit by space shuttle Discovery on April 24, 1990. It is an international collaboration between NASA and the European Space Agency (ESA).

Hubble is one of NASA’s longest-living and most valuable observatories, due to its design allowing it to be repaired and upgraded with advanced technology by astronauts. Today, Hubble continues to provide views of cosmic wonders never before seen and is still at the forefront of astronomy.

Hubble orbits about 547 kilometers above Earth and travels about 5 miles per second. It takes sharp pictures of objects in the sky such as planets, stars, and galaxies. So far it has made more than one million observations including detailed pictures of the birth and death of stars, galaxies billions of light-years away, and comet pieces crashing into Jupiter's atmosphere. 

(Image credit: NASA/UNSPLASH)