NASA announced that Jupiter's icy moon Ganymede has water vapor in its atmosphere. The moon holds the title for the largest moon in the Solar System, which is almost 40% larger than Earth.
This significant discovery could signal the possibility that water vapor is expected in the atmosphere of icy bodies in the Solar System.
Water Vapor Detected in Ganymede's Atmosphere
According to Popular Science, NASA scientists detected ribbons of electrified gas, called auroral bands, in Ganymede's atmosphere based on the ultraviolet images they took in 1998. At that time, they attributed the auroral bands to the oxygen present in the atmosphere of Jupiter's icy moon.
However, 20 years later, NASA scientists studied old and new Hubble Space Telescope information of Ganymede's atmosphere and discovered that prior assumptions about the ice moon's atmosphere were wrong.
In their study, titled "A Sublimated Water Atmosphere on Ganymede Detected from Hubble Space Telescope Observations," published in Nature Astronomy, the team wrote that those auroral bands were due to water vapor in Ganymede's atmosphere.
"It was a challenging measurement, and it was surprising that our technique worked, but we had every expectation that [water vapor] would be there," said study co-author and professor Kurt Retherford, as quoted by PopSci.
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Where Did the Water Vapor Come From?
The auroral bands NASA scientists saw on Ganymede's atmosphere in 1998 proved that the icy moon has a permanent magnetic field. However, discrepancies in the decades-old data showed that these colorful bands of electrified gas are not due to high concentrations of atomic oxygen.
CBS News reported that more recent research data of the Hubble's Cosmic Origins Spectrograph showed that temperatures in Ganymede's atmosphere rise and fall throughout the day. It is warm enough at noontime for sublimation to occur near the moon's equator, releasing water molecules. Sublimation is the transition of a substance from solid to gas, skipping the liquid phase.
Water vapor has always been present in Ganymede's atmosphere, according to study lead author Lorenz Roth, but this discovery was only made possible when data from 1998 was combined with new data and predictions from various studies to give scientists an idea of what to look for and where to look for it.
"There are likely many more things to discover in the gigantic dataset that the Hubble Space Telescope has accumulated over its three decades in space," Roth said, as quoted by CBS.
Astronomers said that finding evidence of water beyond Earth is a significant discovery in searching for other habitable planets. After all, there is a possibility that life could be present in places where there is water.
The European Space Agency (ESA) hopes to find out more about the icy moon when it launches its Jupiter Icy Moons Explorer (JUICE) in 2022, which is planned to arrive in the icy giant by 2029 to observe the planet and its natural satellites for potential habitats.
Roth said that a watery atmosphere might be familiar among icy bodies in the Solar System, Space.com reported. That means detecting water vapor in the atmospheres of other planets is possible in the future.
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