Salts and organic materials observed on the surface of Ganymede by NASA’s Juno

Data collected by NASA’s Juno mission suggests that a salty past may be surfacing on Jupiter’s largest moon.

NASA’s Juno mission detected mineral salts and organic compounds on the surface of Jupiter’s moon Ganymede. Data for this discovery were collected by the Jovian InfraRed Auroral Mapper (JIRAM) spectrometer on board the spacecraft during a flyby of the icy moon. The results, which could help scientists better understand the origin of Ganymede and the composition of its deep oceans, were published on October 30 in the journal Ganymede. Nature astronomy.

Larger than the planet Mercury, Ganymede is the largest of Jupiter’s moons and has long been of great interest to scientists because of the vast inner ocean of water hidden beneath its icy crust. Previous spectroscopic observations conducted by NASA Galileo Spacecraft and Hubble Space Telescope The European Southern Observatory’s Very Large Telescope also hinted at the presence of salts and organic materials, but the spatial resolution of those observations was too low to determine.

On June 7, 2021, Juno flew over Ganymede At an altitude of at least 650 miles (1,046 kilometers). Shortly after the time of closest approach, the JIRAM instrument captured infrared images and infrared spectra (essentially chemical fingerprints of materials, based on how they reflect light) of the moon’s surface. JIRAM, built by the Italian space agency, Agenzia Spaziale Italiana, is designed to capture infrared light (invisible to the naked eye) emerging from deep within Jupiter, to examine the weather layer down to a depth of 30 to 45 miles (50 to 70 kilometers) below. Gas giant cloud tops. But the instrument has also been used to provide insight into the topography of the moons Io, Europa, Ganymede, and Callisto (collectively known as Satellite). Moons of Galilee For their discoverer Galileo).

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JIRAM data for Ganymede obtained during the flyby achieved unprecedented spatial resolution for infrared spectroscopy – better than 0.62 miles (1 km) per pixel. Using it, Juno scientists were able to detect and analyze unique spectral features of non-water-ice materials, including aqueous sodium chloride, ammonium chloride, sodium bicarbonate, and possibly aliphatic aldehydes.

“The presence of ammonia salts suggests that Ganymede may have accumulated material cold enough to condense ammonia during its formation,” said Federico Tosi, Juno mission co-investigator from the Italian National Institute of Astrophysics in Rome and lead author of the study. “The carbonate salts could be the remains of carbon dioxide-rich ice.”

Explore other Jovian worlds

Previous modeling Ganymede’s magnetic field The Moon’s equatorial region, up to about 40 degrees latitude, is protected from energetic electron and heavy ion bombardment resulting from Jupiter’s infernal magnetic field. The presence of these particle flows is known to negatively affect salts and organic matter.

During the June 2021 flyby, JIRAM covered a narrow range of latitudes (10°N to 30°N) and a wider range of longitudes (35°E to 40°E) in the Jupiter-facing hemisphere.

“We found the greatest abundance of salts and organic materials in Dark and bright terrain “At latitudes where the magnetic field protects,” said Juno mission principal investigator Scott Bolton of the Southwest Research Institute in San Antonio. “This suggests that we are seeing the remains of a deep ocean brine that has reached the surface of this frozen world.”

Ganymede is not the only subterranean world that Juno passed through. Europa, which is thought to have an ocean beneath its icy crust, also came under Juno’s gaze for the first time October 2021 And then in September 2022. now Io receives levitation treatment. The next approach to this volcano-filled world is scheduled for December 30, when the spacecraft will reach within 932 miles (1,500 kilometers) of Io’s surface.

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More about the mission

NASA’s Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, California, manages the Juno mission for principal investigator Scott Bolton, of the Southwest Research Institute in San Antonio. Juno is part of NASA’s New Frontiers Program, which is managed at NASA’s Marshall Space Flight Center in Huntsville, Alabama, for the agency’s Science Mission Directorate in Washington. The Italian Space Agency (ASI) funded the Jovian InfraRed Auroral Mapper. Lockheed Martin Space in Denver built and operates the spacecraft.

More information about Juno is available at:

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Jet Propulsion Laboratory, Pasadena, California.

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NASA headquarters in Washington
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Deb Schmid
Southwest Research Institute, San Antonio

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National Institute of Astrophysics
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