Ganymede, a moon of Jupiter and the largest moon in the Solar System, 2001. Photo12/Universal Images Group via Getty Image

Key Takeaways

  1. Astronomers have discovered evidence of water vapor in the atmosphere of Jupiter’s moon Ganymede for the first time.
  2. The discovery was made using data from NASA’s Hubble Space Telescope and published in the journal Nature Astronomy.
  3. Previous research suggested that Ganymede may have more water than Earth’s oceans, but the water on its surface is frozen solid due to extremely cold temperatures.
  4. The water vapor found in Ganymede’s atmosphere does not come from its subsurface ocean, but rather from the sublimation of ice on the moon’s surface.
  5. This finding has implications for future missions, such as ESA’s JUICE mission, which will study Ganymede and other Jupiter moons to understand their nature, evolution, and potential habitability.

For the first time, astronomers using NASA’s Hubble Space Telescope have detected the presence of water vapor in the atmosphere of Ganymede, Jupiter’s largest moon. The discovery, published in the journal Nature Astronomy, sheds light on the moon’s composition and potential for habitability. Despite temperatures cold enough to freeze water on Ganymede’s surface, the sublimation process converts ice into gas, resulting in the observed water vapor.

This image presents Jupiter’s moon Ganymede as seen by the NASA’s Hubble Space Telescope in 1996. Ganymede is located half a billion miles (over 600 million km) away, and Hubble can follow changes on the moon and reveal other characteristics at ultraviolet and near-infrared wavelengths. Astronomers have now used new and archival datasets from Hubble to reveal evidence of water vapor in the atmosphere of Jupiter’s moon Ganymede for the first time, which is present due to the thermal escape of water vapor from the moon’s icy surface. Credits: NASA, ESA, John Spencer (SwRI Boulder)

Also Read: Jupiter’s moon Europa may have water where life could exist, say scientists

By analyzing both new and archived data from Hubble, scientists re-examined observations made over the past two decades to find evidence of water vapor. Previous research had hinted at Ganymede’s substantial water content, possibly exceeding that of Earth’s oceans, although it remains trapped below the moon’s icy crust, roughly 100 miles deep. The newfound water vapor does not originate from this subsurface ocean but rather from the sublimation of surface ice.

The team behind the study, led by Lorenz Roth from the KTH Royal Institute of Technology in Stockholm, Sweden, combined data from Hubble’s Cosmic Origins Spectrograph and archival images from the Space Telescope Imaging Spectrograph to measure the amount of atomic oxygen in Ganymede’s atmosphere. Surprisingly, they discovered minimal amounts of atomic oxygen, indicating that another mechanism was responsible for the observed differences in ultraviolet aurora images.

In 1998, Hubble’s Space Telescope Imaging Spectrograph took these first ultraviolet images of Ganymede, which revealed a particular pattern in the observed emissions from the moon’s atmosphere. The moon displays auroral bands that are somewhat similar to aurora ovals observed on Earth and other planets with magnetic fields. This was an illustrative evidence for the fact that Ganymede has a permanent magnetic field. The similarities in the ultraviolet observations were explained by the presence of molecular oxygen. The differences were explained at the time by the presence of atomic oxygen, which produces a signal that affects one UV color more than the other. Credits: NASA, ESA, Lorenz Roth (KTH)

Also Read: Spacecraft will explore habitability of Jupiter’s ocean moons Ganymede 

Further analysis revealed that the distribution of the aurora in the UV images correlated directly with the expected locations of water in the moon’s atmosphere. As Ganymede’s surface temperature fluctuates throughout the day, reaching warmer levels near the equator, small amounts of water molecules are released through sublimation. This finding paves the way for future missions, such as ESA’s JUICE, to explore Ganymede’s potential as a habitable planetary body.

The JUICE mission, scheduled for launch in 2022 and arrival at Jupiter in 2029, aims to study Jupiter and its moons in detail, with a specific focus on Ganymede. By examining Ganymede’s unique magnetic and plasma interactions with Jupiter, JUICE seeks to gain insights into the nature, evolution, and habitability of icy worlds. The recent discovery of water vapor at Ganymede provides valuable information for refining JUICE’s observation plans and maximizing the mission’s scientific output.

NASA’s Juno mission is currently investigating Ganymede and recently released new images of the moon. Juno has been studying the Jovian system since 2016, providing crucial data to understand the formation, evolution, and potential habitability of gas giant planets and their satellites. The Hubble Space Telescope, a collaborative effort between NASA and ESA, continues to play a vital role in unraveling the mysteries of our universe.

Read full article on NASA.GOV

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