Image Credit: NASA/JPL/Space Science Institute

Big news today from Cassini: observations returned from the spacecraft suggest the possibility of liquid water beneath the icy moon’s surface.

Last July, scientists discovered that Enceladus’ southern polar region displayed signs of an envioronment much warmer than had been anticipated on such a small satellite; Enceladus was thought to be an inactive, barren, frozen little world, a mere 498 km (309 mi) in diameter. As Cassini team member Dr. John Spencer put it, “This is as astonishing as if we’d flown past Earth and found that Antarctica was warmer than the Sahara.” Cassini observations at that time also suggested the possibility of active cryovolcanism. Icy volcanic activity was later confirmed in November of 2005 via additional observations, including a pair of stunning images capturing icy plumes rising from Enceladus’ surface into sunlight.

Now, from today’s press release:

Image Credit: NASA/JPL/Space Science Institute

NASA’s Cassini spacecraft may have found evidence of liquid water reservoirs that erupt in Yellowstone-like geysers on Saturn’s moon Enceladus. The rare occurrence of liquid water so near the surface raises many new questions about the mysterious moon.

“We realize that this is a radical conclusion — that we may have evidence for liquid water within a body so small and so cold,” said Dr. Carolyn Porco, Cassini imaging team leader at Space Science Institute, Boulder, Colo. “However, if we are right, we have significantly broadened the diversity of solar system environments where we might possibly have conditions suitable for living organisms.”

High-resolution Cassini images show icy jets and towering plumes ejecting large quantities of particles at high speed. Scientists examined several models to explain the process. They ruled out the idea that the particles are produced by or blown off the moon’s surface by vapor created when warm water ice converts to a gas. Instead, scientists have found evidence for a much more exciting possibility — the jets might be erupting from near-surface pockets of liquid water above 0 degrees Celsius (32 degrees Fahrenheit), like cold versions of the Old Faithful geyser in Yellowstone.

Mission scientists report these and other Enceladus findings in this week’s issue of Science.

“We previously knew of at most three places where active volcanism exists: Jupiter’s moon Io, Earth, and possibly Neptune’s moon Triton. Cassini changed all that, making Enceladus the latest member of this very exclusive club, and one of the most exciting places in the solar system,” said Dr. John Spencer, Cassini scientist, Southwest Research Institute, Boulder, Colo.

“Other moons in the solar system have liquid-water oceans covered by kilometers of icy crust,” said Dr. Andrew Ingersoll, imaging team member and atmospheric scientist at the California Institute of Technology, Pasadena, Calif. “What’s different here is that pockets of liquid water may be no more than tens of meters below the surface.”

How exciting! This discovery yields a host of fascinating questions to ponder, as noted in the press release.

The Cassini spacecraft will make two additional fly-bys of Enceladus in 2008, the first of which will be a close rendezvous, a mere 350 km (220 mi) above the surface. The observations returned from these next encounters should be fantastic; in light of today’s news, I wish we didn’t have to wait two years.

What I find particularly interesting: findings such as this might be herald a change in our perceptions, re-evaluating the possibility of life existing in places not seriously considered before. Dr. Torrence Johnson’s words offer food for thought:

“If we’re finding more of these types of places and the necessary energy sources to have liquid water in these what we had previously regarded as inhospitable environments, it could well be that icy moons around other stars, around planets of other stars, might be the most common places where you would have the right ingredients for life, which is sort of a turnaround from some of the previous thinking.”

For more on this story, visit:

• JPL Podcast: Water Evidence On Saturn’s Moon Enceladus
• Emily Lakdawalla’s weblog at The Planetary Society
  
• Space.com
  
• Spaceflight Now
• MSNBC

Added 10 March, 21:40 CST:

A neat movie has been added to the Cassini website — Cold Faithful (Quicktime)

Big water news from a tiny moon of Saturn.