Moon Rivers—and Oceans?

In addition to revealing the secrets of the solar system’s past, the UVIS project being conducted by UAB physicist Perry Gerakines, Ph.D., could lead to discoveries about the system’s present—including the possibility for life.

“The mantra in NASA is ‘follow the water,’” says Gerakines. “If you’re looking for life, follow the water.” That’s one reason why Saturn’s moon Enceladus intrigues astronomers. Its surface is encased in an icy shell, but in 2005, Cassini discovered a geyser spewing water and other materials into space from Enceladus. Though the geyser doesn’t prove that the moon necessarily has liquid water, an ocean beneath the ice is an exciting possibility. Gerakines explains that a liquid ocean could exist on the frigid moon because of tidal forces; Saturn and its other moons “tug on Enceladus and squash it a little bit,” warming it sufficiently through frictional heating.

Saturn’s largest moon, Titan, has long been a mystery because its thick atmosphere completely obscures the surface. Its atmosphere is full of hydrocarbons, or “the kind of stuff we would call air pollution,” says Gerakines. While considered smog on Earth, these hydrocarbons also are organic molecules integral to many life processes. During Cassini’s initial mission, the space probe Huygens landed on Titan’s surface, finding frozen water with rivers of liquid methane and liquid ethane, used as fuels on Earth. Titan’s landscape is strikingly similar to that of the early Earth, complete with lakes, rivers, dunes, snow, clouds, and perhaps even liquid-water volcanoes. Therefore, probing Titan’s environment could provide clues about the development of our own planet.

While all of Earth’s living things require liquid water, Gerakines notes that there is more to the equation. “Life demands other things: sources of energy for metabolism, sources of fuel or food, and a way to build new structures and cells. Having water is a good hint that this might be a good place to look, but it certainly doesn’t mean that life is there.”