Jupiter's largest moon, Ganymede, peeks out from behind the giant planet in this 2007 Hubble Space Telescope image. Recent research suggests that Ganymede's outer regions may be arranged like a watery layer cake, with alternating bands of liquid water and water ice. [NASA/ESA/E. Karkoschka (Univ. Arizona)]
Venus and Jupiter
The solar system’s largest moon may be built like a layer cake — with real frosting.
Ganymede is the largest moon of Jupiter — about half again the diameter of our own Moon. It has a solid core of rock and metal, and a crust made of ice. Spacecraft revealed that there’s probably a deep ocean of liquid water far below the crust, with a rime of ice at its bottom.
But a recent study led by Steve Vance of the Jet Propulsion Laboratory suggested a more complex structure. The team used computer models that account for the water’s mineral content, the extreme pressures at great depths, and other factors. The models indicate that a layer of dense liquid water sits at the bottom of the layer cake, with alternating layers of ice and liquid water above it — up to six layers in all, spanning hundreds of miles.
If water is in direct contact with Ganymede’s rocky center, then mineral-rich hot water could percolate up from the rock. That would provide the main ingredients for life: water, energy, and nutrients. So if the layered structure is confirmed, then Ganymede might move up a bit in the list of worlds that are considered possible homes for living organisms.
Jupiter is climbing away from the Sun in the dawn sky. Tomorrow, it’s a bit below Venus, the brilliant “morning star,” and shines quite brightly on its own. It’ll pass Venus over the following couple of mornings, then pull away as it climbs higher into the sky each day.
Script by Damond Benningfield, Copyright 2014
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