Is Jupiter Ganymede’s moon habitable? Scientists make vital discovery

A 23-year-old mystery on the largest moon in our solar system has been resolved.

In 1998, NASA’s Hubble Space Telescope captured Jupiter Ganymede’s moon in ultraviolet light. The images revealed a mysterious pattern of streaks painted on the Jovian moon – auroral bands similar to those seen on Earth.

But something in the data didn’t match. Ganymede’s aurora indicated the presence of oxygen on the large moon, but scientists doubted there was so much oxygen in its atmosphere.

New information from Hubble’s Cosmic Origins Spectrograph (COS) and archival footage from the Space Telescope Imaging Spectrograph (STIS) from 1998 to 2010 found a culprit behind this mysterious phenomenon: Ganymede releases water vapor from its surface icy. The recent findings are detailed in a study published Monday in the journal Nature astronomy and provide scientists with valuable information about other frozen moons in the solar system that may harbor water and the possibility of life.

Ganymede is not only the largest known moon of Jupiter, it is also the largest in the entire solar system. It is even larger than the planet Mercury.

Previous evidence suggested that Ganymede contained more water than all of Earth’s oceans combined. But the moon’s body of water is likely buried hundreds of miles below its surface, as its freezing temperatures would freeze any water on its surface.

WHAT’S NEW – Following on from Hubble’s observations of Ganymede in 1998, the scientists behind the new study set out to measure the amount of atomic oxygen in Ganymede’s atmosphere:

• Both patterns in the ultraviolet images indicated that Ganymede had molecular oxygen, which is made up of two oxygen atoms that are produced when charged particles erode the moon’s icy surface.
• But the ultraviolet emissions did not correspond to an atmosphere with so many oxygen molecules. Instead, they were more likely caused by atomic oxygen, which is made up of a single atom of oxygen.
• In 2018, Ganymede’s follow-up observations revealed that there was virtually no atomic oxygen in his atmosphere.

So what could be behind the two distinct patterns of auroral features on Ganymede?

Scientists have found that Ganymede’s temperatures vary throughout the day. Around noon, the temperature on the moon becomes relatively warm near the equator. This rise in temperature causes small amounts of water molecules to escape from the moon’s icy surface.

“The water vapor that we have now measured comes from the sublimation of ice caused by the thermal escape of H2O vapor from hot and icy regions,” said Lorenz Roth of the Royal KTH Institute of Technology in Stockholm, in Sweden, and lead author of the new study, said in a report.

Essentially, water vapor escapes from Ganymede’s surface, causing molecules to be detected in the lunar atmosphere.

HERE IS THE CONTEXT – Jupiter has a total of 79 known moons.

Ganymede represents one of the many icy moons in the Outer Solar System that offer scientists the opportunity to study habitability in unlikely places.

Saturn’s moon Enceladus also has evidence of an underground ocean and plumes of water ice and steam rising from the moon’s south polar region, making it one of the most potentially habitable places in the system. solar. Europa, another large moon of Jupiter, also has a substantial subsurface ocean and smaller vapor plumes.

When looking for habitability outside of Earth, scientists often look for water as one of the primary indicators that a celestial object might harbor some form of life.

Frozen moons like Ganymede and Enceladus may not look like Earth, but they could be habitable in their own way.

AND AFTER – Ganymede will soon have his own mission.

The European Space Agency is launching the JUpiter ICy moons Explorer, which will begin exploration of Ganymede, as well as two other moons Callisto and Europa, in 2030. NASA’s Europa Clipper, which is expected to arrive in the system the same year, will have also some overflights of Ganymede.

“Our results can provide JUICE instrument teams with valuable information that can be used to refine their observation plans to optimize spacecraft usage,” said Roth.

Abstract: Ganymede’s atmosphere is produced by spraying charged particles and sublimating its icy surface. Earlier far ultraviolet observations of oxygen emissions OI 1356-˚A and OI 1304-˚A were used to derive pulverized molecular oxygen (O2) as an atmospheric component, but an expected component of water sublimated (H2O) was not detected. Here we present an analysis of high sensitivity spectra and spectral images acquired by the Hubble Space Telescope revealing H2O in the Ganymede atmosphere. The relative intensity of oxygen emissions requires contributions from the dissociative excitation of water vapor, indicating that H2O is more abundant than O2 around the subsolar point. Far from the subsolar region, the emissions correspond to an atmosphere of pure O2. Observations of eclipses force atomic oxygen to be at least two orders of magnitude less abundant than these other species. The higher H2O / O2 ratio above the warmer rear hemisphere compared to the colder front hemisphere, the spatial concentration in the sub-solar region and the estimated abundance of ∼1015 H2O / cm2 are consistent with the sublimation of the frozen surface as a source.