NASA’s Juno Mission Detects Salts and Organic Compounds on the Surface of Ganymede; Will They Set the Stage for Habitability?

NASA's Juno mission has made a groundbreaking discovery during its flyby of Ganymede. For the first time, the spacecraft has detected mineral salts and organic compounds on its surface, shedding light on its composition and formation.

Mysteries Surrounding Ganymede

Ganymede has always been a subject of fascination for scientists. Being Jupiter's largest moon, this body measures 3,270 miles (5,268 km) wide, even surpassing the size of Mercury. It is no wonder that astronomers look for more opportunities to discover more information about this enigmatic moon.

A vast internal ocean of water lies behind the icy crust of Ganymede. Beyond water ice, the surface composition of icy moons has become a question with significant implications. Subsurface liquid water oceans, if present, may interact with the icy surfaces above, directly bearing on ocean habitability and detecting possible signs of life.

NASA's Galileo spacecraft and Hubble Space Telescope had made previous spectroscopic observations of this moon in collaboration with the European Southern Observatory's Very Large Telescope. Their investigations hinted at the presence of salts and organic compounds, but their spatial resolution was too low to confirm the discovery.

Evidence of Life-Supporting Elements

The Jovian InfraRed Auroral Mapper (JIRAM) aboard the Juno spacecraft has provided significant data to planetary scientists at NASA. It allowed astronomers to detect hydrated sodium chloride, ammonium chloride, sodium/ ammonium carbonate, and organic compounds on the surface of Ganymede.

On June 7, 2021, Juno made a flyby of Ganymede at a minimum height of 650 miles (1,046 km). It covered a narrow range of latitudes (10-30 degrees north) and a broader range of longitudes (-35 - 40 degrees east) in the hemisphere that faces Jupiter.

Shortly after the closest approach, the JIRAM instrument captured infrared images and spectra of the icy moon's surface. The data obtained achieved an unprecedented spatial resolution for infrared spectroscopy, better than 0.62 miles (1 km) per pixel.

With this data, scientists could detect and analyze the unique spectral characteristics of non-water-ice materials, such as sodium bicarbonate, sodium chloride, ammonium chloride, and possibly aliphatic aldehydes.

According to Dr. Federico Tosi from Italy's National Institute for Astrophysics, the presence of ammoniated salts suggests that the icy moon may have accumulated materials cold enough to condense ammonia during its formation. The carbonate salts could be the remnants of ice rich in carbon dioxide.

Early models of Ganymede's magnetic field reveal that the moon's equatorial region is protected from the energetic electron and heavy ion bombardment. The presence of these particles has been known to affect salts and organic materials.

The research team found the greatest abundance of salts and organics in the dark and bright terrains in regions protected by the magnetic field. This suggests the discovery of a deep ocean brine that reached the surface of Ganymede.

Juno's mission has been extended twice, and the spacecraft will continue to orbit Jupiter until September 2025. With each flyby, the mission offers valuable information that enables scientists to understand better the gas giants and moons in our Solar System.