With Europa and Enceladus getting most of the attention for their subsurface oceans and their ability to host life, other frozen worlds have been left in the shadows, but Jupiter’s mysterious moon Ganymede is now making headlines.
While Ganymede has not yet been observed spewing plumes of water vapor like Saturn’s moon Enceladus, Jupiter’s largest moon likely hides a massive ocean of salty water. Hubble notes These results suggest that the ocean – thought to be under 150 kilometers (95 miles) of ice – could be up to 100 kilometers (60 miles) deep. This is ten times deeper than the ocean on Earth.
Ganymede is having a special moment because NASA’s Juno mission noticed salts and organic compounds on its surface, possibly from an ocean beneath the ice crust. While Juno’s observations can’t provide conclusive evidence that this moon has an ocean that makes Earth look like a kiddie pool, Juno’s findings are the strongest evidence yet of salts and other chemicals reaching the outside of Ganymede.
It is already known that the surface of Ganymede is made of water ice. Juno’s JIRAM (Jovian Infrared Auroral Mapper) instrument has now used its infrared vision to identify materials including aqueous salts, ammonia, sodium bicarbonate, hydrated silica, and what could be… Aliphatic aldehydesWhich can build more complex organic compounds. Hydrous salt (hydrous sodium chloride) may indicate the presence of a salty ocean beneath the surface ice. Juno mission scientists believe that the ammonia salt (ammonium chloride) found on the surface may mean that as Ganymede formed, material cool enough to condense the ammonia somehow accumulated. Carbonate salts may be leftover ice rich in carbon dioxide.
“The composition and spatial distribution of these salts and organic materials suggest that they are endogenous in origin, resulting from the extrusion of subsurface brines, whose chemistry reflects the interaction between water and rock within Ganymede,” the scientists wrote in a study recently published in the journal Nature.
Anything that is endogenous originates from within the moon, planet, or other body, while exogenous materials originate on the surface. If the salts and organic materials present are indeed endogenous, it means they somehow rose from the depths of Ganymede. They may have traveled in water that oozed through cracks in the surface rather than being ejected in plumes of steam, like those found on Enceladus.
Jerram did not find exogenous compounds such as hydrogen peroxide or hydrous sulfuric acid, both of which are found on the surface of Europa, another frozen Jovian world, although they were discovered near Ganymede’s poles in 2010. Previous studies. The lack of exogenous compounds (at least based on what JIRAM was able to see) in these salty deposits may be evidence that the detected compounds came from a salty ocean.
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Whether the compounds found by JIRAM actually originated deep underground or near the surface remains unknown. Without definitive proof of the existence of that ocean, Juno scientists also acknowledge the possibility that organic materials and salts could have somehow originated in the shallow layers of the crust. Ganymede’s crust is much thicker than Europa’s, which means it would be difficult for any material from the subsurface ocean to pass through that crust.
Communications have been made Between aliphatic aldehydes and liquid water activity, at least on Earth. Other researchers have also seen what may be signs of its presence in plumes of water vapor emanating from Enceladus. If so, this would strengthen the argument for a subsurface oceanic origin, as Enceladus’s vapor also contains some of the same salts found on Ganymede’s surface, and these salts are considered endogenous. They are thought to come from interactions between liquid water and rocks, especially silicate rocks.
The discovery of organic materials and aliphatic aldehydes on Ganymede inevitably raises another question: Does Ganymede have what it takes to support life? may be. Aliphatic aldehydes, which have been found in some types of carbonaceous meteorites that have fallen to Earth, are precursors of carboxylic acids and amino acids. Alien researchers shouldn’t get too excited about this. Organic matter is everywhere in space, so its presence on Ganymede shouldn’t be too surprising. However, this can continue to excite the imagination of those who want to believe.
Physical Astronomy, 2023. DOI: 10.1038/s41550-023-02107-5
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