The trailing hemisphere of Jupiter’s moon Europa as imaged by Galileo. Photo Credit: NASA

The Search for Alien Life Part 2: In the Realm of the Gas Giants

By David Darling

Beyond the main asteroid belt lie the giant planets Jupiter and Saturn and their impressive retinues of moons. What chances for life are out here in the frozen wastes of the solar system? At first glance, you’d imagine none. The planets themselves have no solid surface (unless you go thousands of miles down), and their moons are bitterly cold, with surface temperatures of minus 160 C or less. Life as we know it needs liquid water (plus some source of energy and carbon-containing substances), and there might seem no hope of finding water so far from the Sun.

But, as early as the 1970s, theorists had begun to speculate that some of the larger moons of Jupiter, especially Europa, might have their interiors warmed up through tidal heating. This process involves flexing of the moon as it moves around its orbit and interacts gravitationally with nearby satellites and Jupiter itself. The result might be a subsurface ocean of liquid water.

These suspicions were confirmed by images and other data sent back by the Galileo probe during its eight-year exploration of the Jovian system from 1995 to 2003. The evidence is now compelling that Europa has a large saltwater ocean, hidden under several kilometers or more of ice. Subsurface oceans might also exist on two of Jupiter’s other moons, Ganymede and Callisto, on Saturn’s Titan and Enceladus, and on Neptune’s Triton. In fact, such bodies of water could be incredibly common throughout the galaxy. The big question is: are they capable of supporting life?

Read more: The Search for Alien Life Part 2: In the Realm of the Gas Giants « AmericaSpace.

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