NASA's Cassini Discovers Potential Liquid Water on Enceladus
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.
Image right: Plumes of icy material extend above the southern polar region of Saturn’s moon Enceladus as imaged by the Cassini spacecraft in February 2005. The monochrome view is presented along with a color-coded version on the right. The latter reveals a fainter and much more extended plume component. + Full caption
"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."
Other unexplained oddities now make sense. "As Cassini approached Saturn,
we discovered that the Saturnian system is filled with oxygen atoms. At
the time we had no idea where the oxygen was coming from," said Dr. Candy
Hansen, Cassini scientist at NASA's Jet Propulsion Laboratory in Pasadena.
"Now we know that Enceladus is spewing out water molecules, which break
down into oxygen and hydrogen."
Scientists are also seeing variability at Enceladus. "Even when Cassini is
not flying close to Enceladus, we can detect that the plume's activity has
been changing through its varying effects on the soup of electrically-charged
particles that flow past the moon," said Dr. Geraint H. Jones, Cassini scientist,
magnetospheric imaging instrument, Max Planck Institute for Solar System Research,
Scientists still have many questions. Why is Enceladus currently so active?
Are other sites on Enceladus active? Might this activity have been continuous
enough over the moon's history for life to have had a chance to take hold in
the moon's interior?
"Our search for liquid water has taken a new turn. The type of evidence for
liquid water on Enceladus is very different from what we've seen at Jupiter's
moon Europa. On Europa the evidence from surface geological features points to
an internal ocean. On Enceladus the evidence is direct observation of water vapor
venting from sources close to the surface," said Dr. Peter Thomas, Cassini
imaging scientist, Cornell University, Ithaca, N.Y.
In the spring of 2008, scientists will get another chance to look at Enceladus
when Cassini flies within 350 kilometers (approximately 220 miles), but much
work remains after Cassini's four-year prime mission is over.
"There's no question that, along with the moon Titan, Enceladus should be a
very high priority for us. Saturn has given us two exciting worlds to explore,"
said Dr. Jonathan Lunine, Cassini interdisciplinary scientist, University of
Arizona, Tucson, Ariz.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space
Agency and the Italian Space Agency. JPL, a division of the Caltech, manages the
mission for NASA's Science Mission Directorate. The Cassini orbiter was designed,
developed and assembled at JPL.
For images and more information, visit: http://www.nasa.gov/cassini
Carolina Martinez (818) 354-9382
Jet Propulsion Laboratory, Pasadena, Calif.
Erica Hupp/Dwayne Brown (202) 358-1237/1726
NASA Headquarters, Washington