NASA announced on Monday that astronomers have detected water vapor in the atmosphere of Jupiter’s largest moon Europa for the first time.
Scientists arrived at this discovery by examining new and old data from NASA’s Hubble Space Telescope over the past two decades, and published their findings in the journal Natural Astronomy.
Previous studies have found that Ganymede is the largest satellite in the solar system, and its water content is more than that of all the oceans on Earth. But according to NASA, the temperature there is so low that the water on the moon’s surface freezes into a solid, and the moon’s ocean is about 100 miles below the ice crust.
Therefore, scientists speculate that the water vapor found cannot come from the evaporation of the underground ocean, but from the evaporation of ice on the surface of Ganymede.
The Hubble telescope used by astronomers to discover water vapor took the first ultraviolet image of Ganymede in 1998 and discovered the presence of molecular and atomic oxygen.
In 2018, Lorenz Roth of the KTH Royal Institute of Technology in Stockholm, Sweden, led a NASA team to measure atomic oxygen content with the Hubble Telescope. They studied data from 1998 to 2010, but the results revealed the existence of water vapor.
Although scientists have found almost no atomic oxygen in Ganymede’s atmosphere compared with the data in 1998, they have learned that the surface temperature varies greatly throughout the day and may become warm enough around noon. Some small amounts of water molecules are released.
“So far, only molecular oxygen has been observed,” Mr. Ross told NASA. “This is produced when charged particles erode the ice surface. The water vapor we are measuring now comes from the sublimation of the ice caused by the thermal escape of water vapor from a warm, cold area.”
NASA’s Juno mission is studying new images of Ganymede and the ice moon. In June, the Juno spacecraft flew over Europa, which was the first close contact with a celestial body since Galileo flew over it in May 2000.
NASA said that the flyby not only took pictures of the moon, but also allowed scientists to understand the moon’s composition, ionosphere, magnetosphere, and ice crust. The spacecraft will also measure the radiation environment near Europa.
Juno will return next year to take a closer look at Jupiter’s other large moons, including Europa and Europa.
Since 2016, Juno has been studying Jupiter and its environment, also known as the Jupiter system.