Southside

Thoughts of a Newtown Socialist

Friday, June 26, 2009

Is There Life on Enceladus?


Ever since the Galileo probe left to orbit Jupiter and pass by some of its moons, I have been interested in the possibility of life in other parts of the Solar System (apart from Earth). Scientists were and are still speculating that Europa has a liquid ocean under its ice but Galileo could not determine whether it has.

In 2005 the Cassini probe, which is orbiting Saturn discovered a geyser coming from near the south pole of one of its icy moons Enceladus. There is debate over whether this is due to a liquid ocean beneath the surface. Below is the latest finding, which suggests there is. It is a news release from NASA released last Thursday.

RELEASE: 09-147

SALT FINDING FROM NASA'S CASSINI HINTS AT OCEAN WITHIN SATURN MOON

PASADENA, Calif. -- For the first time, scientists working on NASA's
Cassini mission have detected sodium salts in ice grains of Saturn's
outermost ring. Detecting salty ice indicates that Saturn's moon
Enceladus, which primarily replenishes the ring with material from
discharging jets, could harbor a reservoir of liquid water -- perhaps
an ocean -- beneath its surface.

Cassini discovered the water-ice jets in 2005 on Enceladus. These jets
expel tiny ice grains and vapor, some of which escape the moon's
gravity and form Saturn's outermost ring. Cassini's cosmic dust
analyzer has examined the composition of those grains and found salt
within them.

"We believe that the salty minerals deep inside Enceladus washed out
from rock at the bottom of a liquid layer," said Frank Postberg,
Cassini scientist for the cosmic dust analyzer at the Max Planck
Institute for Nuclear Physics in Heidelberg, Germany. Postberg is
lead author of a study that appears in the June 25 issue of the
journal Nature.

Scientists on Cassini's cosmic dust detector team conclude that liquid
water must be present because it is the only way to dissolve the
significant amounts of minerals that would account for the levels of
salt detected. The process of sublimation, the mechanism by which
vapor is released directly from solid ice in the crust, cannot
account for the presence of salt.

"Potential plume sources on Enceladus are an active area of research
with evidence continuing to converge on a possible salt water ocean,"
said Linda Spilker, Cassini deputy project scientist at NASA's Jet
Propulsion Laboratory in Pasadena, Calif. "Our next opportunity to
gather data on Enceladus will come during two flybys in November."

The makeup of the outermost ring grains, determined when thousands of
high-speed particle hits were registered by Cassini, provides
indirect information about the composition of the plume material and
what is inside Enceladus. The outermost ring particles are almost
pure water ice, but nearly every time the dust analyzer has checked
for the composition, it has found at least some sodium within the
particles.

"Our measurements imply that besides table salt, the grains also
contain carbonates like soda. Both components are in concentrations
that match the predicted composition of an Enceladus ocean," Postberg
said. "The carbonates also provide a slightly alkaline pH value. If
the liquid source is an ocean, it could provide a suitable
environment on Enceladus for the formation of life precursors when
coupled with the heat measured near the moon's south pole and the
organic compounds found within the plumes."

However, in another study published in Nature, researchers doing
ground-based observations did not see sodium, an important salt
component. That team notes that the amount of sodium being expelled
from Enceladus is actually less than observed around many other
planetary bodies. These scientists were looking for sodium in the
plume vapor and could not see it in the expelled ice grains. They
argue that if the plume vapor does come from ocean water the
evaporation must happen slowly deep underground rather than as a
violent geyser erupting into space.

"Finding salt in the plume gives evidence for liquid water below the
surface," said Sascha Kempf, also a Cassini scientist for the cosmic
dust analyzer from the Max Planck Institute for Nuclear Physics. "The
lack of detection of sodium vapor in the plume gives hints about what
the water reservoir might look like."

Determining the nature and origin of the plume material is a top
priority for Cassini during its extended tour, called the Cassini
Equinox Mission.

"The original picture of the plumes as violently erupting
Yellowstone-like geysers is changing," said Postberg."They seem more
like steady jets of vapor and ice fed by a large water reservoir.
However, we cannot decide yet if the water is currently 'trapped'
within huge pockets in Enceladus' thick ice crust or still connected
to a large ocean in contact with the rocky core."

The Cassini-Huygens mission is a cooperative project of NASA, the
European Space Agency and the Italian Space Agency. The Cassini
cosmic dust analyzer was provided by the German Aerospace Center. The
Cassini orbiter was designed, developed and assembled at JPL. JPL
manages the mission for the Science Mission Directorate at NASA
Headquarters in Washington.

More information about the Cassini mission is available at:

http://www.nasa.gov/cassini

-end-

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