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Organics and Salts Identified on Ganymede, Jupiter’s Largest Moon, by NASA’s Juno Mission
An advanced image of Ganymede, Jupiter’s largest moon, was captured by the JunoCam imager on NASA’s Juno spacecraft during a flyby conducted on June 7, 2021. The data collected from this mission has been instrumental in confirming the existence of both salts and organic materials on Ganymede. Credit: NASA/JPL-Caltech/SwRI/MSSS/Kalleheikki Kannisto © CC BY
Information acquired from NASA’s Juno spacecraft suggests that Jupiter’s largest moon, Ganymede, may be exhibiting signs of a saline past on its surface.
NASA’s Juno spacecraft has revealed the presence of mineral salts and organic compounds on Ganymede, Jupiter’s biggest moon. The data for this finding was obtained via the Jovian InfraRed Auroral Mapper (JIRAM) spectrometer aboard the spacecraft during a close encounter with this icy moon. Published on October 30 in the journal Nature Astronomy, these discoveries could potentially enrich our understanding of Ganymede’s origins as well as the composition of its deep ocean.
Ganymede, larger than the planet Mercury, has long captivated the scientific community due to the expansive internal ocean concealed beneath its icy shell. Earlier observations from NASA’s Galileo spacecraft, the Hubble Space Telescope, and the European Southern Observatory’s Very Large Telescope had alluded to the presence of salts and organics, but their spatial resolution was insufficient for definitive conclusions.
During a flyby on June 7, 2021, NASA’s Juno spacecraft approached Jupiter’s frozen moon Ganymede at a closer distance than any other spacecraft had in over twenty years. Less than a day later, the spacecraft executed its 34th flyby of Jupiter. For both celestial bodies, imagery from JunoCam was processed and incorporated into a digital sphere to construct a flyby animation. Supplementary frames were added to offer perspectives of both the approach and departure for Ganymede and Jupiter. Credit: NASA/JPL-Caltech/SwRI/MSSS
Detailed Observations by Juno
On the aforementioned date, Juno flew above Ganymede at an altitude as low as 650 miles (1,046 kilometers). Subsequent to this closest approach, the JIRAM instrument onboard the spacecraft gathered infrared images and spectra, effectively capturing the chemical composition of the moon’s surface. The instrument, engineered by the Italian Space Agency, Agenzia Spaziale Italiana, was initially designed to examine the infrared emissions from deep within Jupiter. However, it has also been employed to gain insights into the Galilean moons—Io, Europa, Ganymede, and Callisto—named after their discoverer, Galileo.
JIRAM’s data from the Ganymede flyby achieved an unparalleled spatial resolution for infrared spectroscopy—better than 0.62 miles (1 kilometer) per pixel. The data enabled scientists to identify unique spectral characteristics of non-water-ice substances, including hydrated sodium chloride, ammonium chloride, sodium bicarbonate, and possibly aliphatic aldehydes.
According to Federico Tosi, a Juno co-investigator from Italy’s National Institute for Astrophysics in Rome and lead author of the paper, “The ammoniated salts suggest that Ganymede may have amassed materials at sufficiently low temperatures for ammonia to condense during its formation. The carbonate salts could be the remnants of carbon dioxide-rich ices.”
Investigating Other Moons in Jupiter’s Orbit
Earlier simulations regarding Ganymede’s magnetic field revealed that up to a latitude of around 40 degrees, the moon is safeguarded from the intense electron and heavy ion fluxes generated by Jupiter’s powerful magnetic field, which are known to adversely affect salts and organics. During the 2021 flyby, JIRAM scanned latitudinal ranges from 10 to 30 degrees north and longitudinal ranges from minus 35 to 40 degrees east in the hemisphere facing Jupiter.
Scott Bolton, Juno’s principal investigator from the Southwest Research Institute in San Antonio, noted, “The highest concentrations of salts and organics were found in terrains at latitudes that are shielded by the magnetic field, suggesting that these might be residues of a once-deep ocean brine that has surfaced.”
In addition to Ganymede, Juno has also closely examined Europa, another moon of Jupiter thought to have an underwater ocean. The next scheduled close flyby is set for December 30, targeting Io, a moon notorious for its volcanic activity.
Reference: “Salts and organics on Ganymede’s surface observed by the JIRAM spectrometer onboard Juno” by Federico Tosi et al., published in Nature Astronomy on October 30, 2023. DOI: 10.1038/s41550-023-02107-5
The Juno mission is managed by NASA’s Jet Propulsion Laboratory (JPL), a division of Caltech in Pasadena, California, for its principal investigator, Scott Bolton of the Southwest Research Institute in San Antonio. The mission is a component of NASA’s New Frontiers Program, overseen by NASA’s Marshall Space Flight Center in Huntsville, Alabama, for the Science Mission Directorate in Washington. Funding for the Jovian InfraRed Auroral Mapper was provided by the Italian Space Agency, while Lockheed Martin Space in Denver constructed and operates the spacecraft.
Frequently Asked Questions (FAQs) about Juno Mission Discovers Organics on Ganymede
What was the primary discovery made by NASA’s Juno mission on Ganymede?
The Juno spacecraft detected the presence of mineral salts and organic compounds on the surface of Jupiter’s largest moon, Ganymede. The data for this significant finding was collected by the Jovian InfraRed Auroral Mapper (JIRAM) spectrometer during a close flyby of the moon.
When did Juno make this discovery about Ganymede?
The discovery was made during a flyby on June 7, 2021. The findings were published in the journal Nature Astronomy on October 30.
How did Juno gather this data?
The spacecraft employed the Jovian InfraRed Auroral Mapper (JIRAM) spectrometer to capture infrared images and spectra—essentially the chemical fingerprints—of Ganymede’s surface. This information was used to identify the presence of mineral salts and organic compounds.
How close did the Juno spacecraft get to Ganymede during the flyby?
During its closest approach, Juno was at a minimum altitude of 650 miles (1,046 kilometers) from Ganymede’s surface.
What does this discovery imply about Ganymede’s history or composition?
The presence of mineral salts and organic compounds could provide insights into the origin and composition of Ganymede, including its deep ocean. It suggests that the moon may have had a briny past and possibly a complex chemical history.
What was the spatial resolution of the JIRAM instrument?
The JIRAM data obtained during the flyby achieved an unprecedented spatial resolution for infrared spectroscopy, better than 0.62 miles (1 kilometer) per pixel.
Was Juno specifically designed for this kind of research?
While Juno was primarily designed to study Jupiter, its JIRAM instrument has also been employed to study the terrain of Jupiter’s moons, including Ganymede. The instrument was originally intended to capture infrared light emerging from deep inside Jupiter.
Who are the primary organizations and individuals responsible for the Juno mission?
The Juno mission is managed by NASA’s Jet Propulsion Laboratory (JPL), a division of Caltech in Pasadena, California. The principal investigator is Scott Bolton from the Southwest Research Institute in San Antonio. The Italian Space Agency funded the Jovian InfraRed Auroral Mapper, and Lockheed Martin Space built and operates the spacecraft.
Are there plans to study other Jovian moons?
Yes, Juno has also examined Europa and is scheduled to make a close approach to Io. These moons are collectively known as the Galilean moons, and each presents unique opportunities for scientific discovery.
What is the significance of this discovery for the scientific community?
The discovery of mineral salts and organic compounds on Ganymede could shed light on the moon’s formation and its past. This information is crucial for understanding the broader Jovian system and could have implications for the search for life elsewhere in our solar system.
More about Juno Mission Discovers Organics on Ganymede
- NASA’s Official Juno Mission Page
- Nature Astronomy Journal
- Jovian InfraRed Auroral Mapper (JIRAM) Instrument Details
- Information about Ganymede
- Southwest Research Institute: Juno’s Principal Investigator
- Italian Space Agency
- NASA’s Jet Propulsion Laboratory
- NASA’s New Frontiers Program
- Lockheed Martin Space
