For decades now Jupiter's moon Ganymede has been one of the more interesting objects in our solar system. The moon is one of the few that is known to have a large ocean beneath an icy layer, leading to speculation that primitive life may have evolved somewhere inside.
This week astronomers have announced a discovery that increases the likelihood that Ganymede harbors life. A new study published in the journal Planetary and Space Science has developed a model of Ganymede's seas that is layered between sheets of ice.
"Ganymede's ocean might be organized like a Dagwood sandwich," said Steve Vance, lead author of the study and a researcher at NASA's Jet Propulsion Laboratory (JPL). "This is good news for Ganymede. Its ocean is huge, with enormous pressures, so it was thought that dense ice had to form at the bottom of the ocean. When we added salts to our models, we came up with liquids dense enough to sink to the sea floor."
Vance and his colleagues looked at how dense saltwater ice might behave in the deep high-pressure oceans on Ganymede. Using a new computer model of the moon they showed that the crystal structure of such ice can make it more dense than water, causing the ice to sink. The phenomenon is strange enough that lighter ice formed at the bottom of the sea might actually "snow" upward through the sea.
The new findings do not count out possible life in Ganymede's seas, and could in fact support such ideas. According to the new study the water nearest to Ganymede's core could be salt water, making the possibility of life more likely than if this layer were simply ice.
The study's authors also believe these findings could apply to many of the "super-Earth" exoplanets that have been discovered in recent years. A few of these planets have been found orbiting in their star's habitable zone, meaning liquid water could be maintained on or within them.
Image via NASA/JPL-Caltech