PASADENA, California – NASA’s Juno mission has uncovered evidence of mineral salts and organic compounds on Ganymede, Jupiter’s largest moon. The data collected by the Jovian InfraRed Auroral Mapper (JIRAM) spectrometer during a flyby of the moon revealed these intriguing findings. Scientists hope that this discovery will shed light on Ganymede’s origins and the composition of its deep ocean. The results were published in the journal Nature Astronomy on October 30.

Ganymede, larger than the planet Mercury, has been a subject of interest for scientists due to its hidden ocean of water beneath its icy surface. Previous observations by NASA’s Galileo spacecraft and the Hubble Space Telescope, as well as the European Southern Observatory’s Very Large Telescope, had given hints of the presence of salts and organics. However, the low spatial resolution of these observations prevented a definitive conclusion.

On June 7, 2021, NASA’s Juno spacecraft made a close flyby of Ganymede, coming closer to the moon than any other spacecraft in over twenty years. Shortly after the closest approach, JIRAM obtained infrared images and spectra of Ganymede’s surface. These high-resolution images allowed scientists to detect and analyze the unique spectral features of non-water-ice materials, including hydrated sodium chloride, ammonium chloride, sodium bicarbonate, and possibly aliphatic aldehydes.

Federico Tosi, a Juno co-investigator from Italy’s National Institute for Astrophysics, stated that the presence of ammoniated salts implies 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.

JIRAM’s flyby data has also revealed that the highest abundance of salts and organics is found in the dark and bright terrains at latitudes shielded by Ganymede’s magnetic field. Scott Bolton, Juno’s principal investigator, suggests that these findings indicate the presence of a deep ocean brine that reached the moon’s surface.

The Juno mission has not only observed Ganymede but has also gathered data on other Jovian worlds. In October 2021 and September 2022, Juno captured images of Europa, another moon suspected to have an ocean beneath its icy shell. The spacecraft is now on its way to study Io, a moon characterized by volcanic activity.

In conclusion, NASA’s Juno mission has provided significant evidence of salts and organics on Ganymede, offering valuable insights into the moon’s composition and origins. These findings open new possibilities for understanding the potential habitability of icy worlds in our solar system.