Ganymede is Jupiter\u2019s largest moon, and it\u2019s also the largest moon in the solar system. Like several other icy moons, scientists think that Ganymede has a deep ocean of liquid water beneath its outer ice crust. Now, NASA\u2019s Juno spacecraft has found mineral salts and organic compounds on Ganymede\u2019s surface. The findings suggest that briny water has made its way to the moon\u2019s surface. NASA said on October 30, 2023, that the discovery will help scientists learn more about the composition of the ocean and how the moon itself first formed.<\/p>\n
Researchers in the U.S. and Italy published their peer-reviewed results in Nature Astronomy<\/em> on October 30.<\/p>\n The 2024 lunar calendars are here! Best Christmas gifts in the universe! Check \u2019em out here.<\/p>\n Juno conducted a close flyby of Ganymede on June 7, 2021, coming within 650 miles (1,046 km) of the icy surface. Juno\u2019s Jovian InfraRed Auroral Mapper (JIRAM) spectrometer acquired infrared images and infrared spectra. In general, mission scientists primarily use JIRAM to peer deep into Jupiter\u2019s atmosphere. They have also used it, however, to study the surfaces of Io, Europa, Ganymede and Callisto.<\/p>\n And, in fact, the resolution of the infrared spectroscopy during the flyby was impressive, better than 0.62 miles (1 km) per pixel. Juno found a variety of surface materials, including hydrated sodium chloride, ammonium chloride, sodium bicarbonate and maybe also aliphatic aldehydes.<\/p>\n Federico Tosi is a Juno co-investigator at the National Institute for Astrophysics in Rome, Italy, and lead author of the new paper. He said:<\/p>\n The presence of ammoniated salts suggests that Ganymede may have accumulated materials cold enough to condense ammonia during its formation. The carbonate salts could be remnants of carbon dioxide-rich ices.<\/p>\n<\/blockquote>\n As the paper explained, the composition and distribution of the salts and organics suggests that they originated from within Ganymede (making them endogenous, or endogenic). In fact, they most likely came to the surface in watery brines:<\/p>\n The composition and spatial distribution of these salts and organics suggest that their origin is endogenic, resulting from the extrusion of subsurface brines, whose chemistry reflects the water\u2013rock interaction inside Ganymede.<\/p>\n<\/blockquote>\n In addition, this result is reminiscent of another study that was published last month, showing that carbon-dioxide ice on the surface of Europa came from inside the moon instead of from an external source (exogenous).<\/p>\n So, how do the scientists know that the salts and organics came from below as brines, instead of being created on the surface somehow? One big clue comes from Ganymede\u2019s magnetic field. The magnetic field shields the moon\u2019s surface along the equator up to about 40 degrees latitude. More specifically, the magnetic field blocks electrons and ions that come from Jupiter\u2019s own and more powerful magnetic field. Those electrons and ions can easily damage the mineral salts and organics.<\/p>\n In 2021, during the flyby, Juno\u2019s JIRAM instrument studied Ganymede\u2019s surface from latitudes 10 degrees north to 30 degrees north and longitudes -35 degrees east to 40 degrees east. Those areas include the moon\u2019s characteristic dark and bright regions. Those latitudes are protected by the magnetic field. And \u2013 surprise \u2013 that is where the salts and organics were primarily found. Scott Bolton, Juno\u2019s principal investigator at the Southwest Research Institute in San Antonio, Texas, said:<\/p>\n We found the greatest abundance of salts and organics in the dark and bright terrains at latitudes protected by the magnetic field. This suggests we are seeing the remnants of a deep ocean brine that reached the surface of this frozen world.<\/p>\n<\/blockquote>\n Originally, evidence for Ganymede\u2019s magnetic field first came when the Hubble Space Telescope observed the moon in ultraviolet (UV) light in 1998 and 2010. Images from both observations revealed an aurora zone on Ganymede. This was a sign that the large moon has a permanent magnetic field, produced by an iron core.<\/p>\n Also, in 2021, astronomers using archival data from Hubble found the first evidence of water vapor on Ganymede. Using the old data along with new data, the researchers measured the amount of atomic oxygen in the moon\u2019s tenuous atmosphere. What they found was that the moon Ganymede has hardly any atomic oxygen. In essence, this finding seemed to upend their explanation for differences in the UV auroras.<\/p>\n But then, they looked more closely at where the UV auroral displays were on Ganymede. As it turned out, the locations of Ganymede\u2019s auroras correlated with where they\u2019d expect to find water in Ganymede\u2019s atmosphere, if the moon was releasing water vapor.<\/p>\n Bottom line: NASA\u2019s Juno spacecraft has found salts and organics on Jupiter\u2019s largest moon, Ganymede. They suggest that watery brines came up to the surface from deep below.<\/p>\n Source: Salts and organics on Ganymede\u2019s surface observed by the JIRAM spectrometer onboard Juno<\/p>\n Via NASA<\/p>\n Learn more about the Juno mission<\/p>\n Read more: See 1st new images of Ganymede in over 20 years<\/p>\n Read more: Webb telescope provides unique view of 2 Jupiter moons<\/p>\n <\/div>\nA close flyby of Ganymede<\/h3>\n
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Watery brines<\/h3>\n
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![\"Gray](\"https:\/\/earthsky.org\/upl\/2023\/11\/Juno-JIRAM-Ganymede-grooved-terrain-June-7-2021.jpg\")
Magnetic field protects brines<\/h3>\n
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![\"Darker](\"https:\/\/earthsky.org\/upl\/2023\/11\/Ganymede-dark-bright-terrain-Galileo-May-20-2000.png\")
Water vapor on Ganymede<\/h3>\n