[meteorite-list] NASA Space Assets Detect Ocean Inside Saturn Moon Enceladus
From: Douglas Chenin, DDS <dougchenin_at_meteoritecentral.com>
Date: Thu, 03 Apr 2014 13:12:23 -0700
Thanks Ron, that's exciting news :)
On 4/3/2014 11:44 AM, Ron Baalke wrote:
> April 3, 2014
> NASA Space Assets Detect Ocean inside Saturn Moon
> Gravity measurements by NASA's Cassini spacecraft and Deep Space Network
> suggest that Saturn's moon Enceladus, which has jets of water vapor and ice
> gushing from its south pole, also harbors a large interior ocean beneath an
> ice shell, as this illustration depicts.
> Image Credit: NASA/JPL-Caltech
> NASA's Cassini spacecraft and Deep Space Network have uncovered evidence
> Saturn's moon Enceladus harbors a large underground ocean of liquid water,
> furthering scientific interest in the moon as a potential home to
> extraterrestrial microbes.
> Researchers theorized the presence of an interior reservoir of water in 2005
> when Cassini discovered water vapor and ice spewing from vents near the
> moon's south pole. The new data provide the first geophysical measurements of
> the internal structure of Enceladus, consistent with the existence of a
> hidden ocean inside the moon. Findings from the gravity measurements are in
> the Friday April 4 edition of the journal Science.
> "The way we deduce gravity variations is a concept in physics called the
> Doppler Effect, the same principle used with a speed-measuring radar gun,"
> said Sami Asmar of NASA's Jet Propulsion Laboratory (JPL) in Pasadena,
> Calif., a coauthor of the paper. "As the spacecraft flies by Enceladus, its
> velocity is perturbed by an amount that depends on variations in the gravity
> field that we're trying to measure. We see the change in velocity as a change
> in radio frequency, received at our ground stations here all the way across
> the solar system."
> The gravity measurements suggest a large, possibly regional, ocean about 6
> miles (10 kilometers) deep, beneath an ice shell about 19 to 25 miles (30 to
> 40 kilometers) thick. The subsurface ocean evidence supports the inclusion of
> Enceladus among the most likely places in our solar system to host microbial
> life. Before Cassini reached Saturn in July 2004, no version of that short
> list included this icy moon, barely 300 miles (500 kilometers) in diameter.
> "This then provides one possible story to explain why water is gushing out of
> these fractures we see at the south pole," said David Stevenson of the
> California Institute of Technology, Pasadena, one of the paper's co-authors.
> Cassini has flown near Enceladus 19 times. Three flybys, from 2010 to 2012,
> yielded precise trajectory measurements. The gravitational tug of a planetary
> body, such as Enceladus, alters a spacecraft's flight path. Variations in the
> gravity field, such as those caused by mountains on the surface or
> differences in underground composition, can be detected as changes in the
> spacecraft's velocity, measured from Earth.
> The technique of analyzing a radio signal between Cassini and the Deep Space
> Network can detect changes in velocity as small as less than one foot per
> hour (90 microns per second). With this precision, the flyby data yielded
> evidence of a zone inside the southern end of the moon with higher density
> than other portions of the interior.
> The south pole area has a surface depression that causes a dip in the local
> tug of gravity. However, the magnitude of the dip is less than expected given
> the size of the depression, leading researchers to conclude the depression's
> effect is partially offset by a high-density feature in the region, beneath
> the surface.
> "The Cassini gravity measurements show a negative gravity anomaly at the
> south pole that however is not as large as expected from the deep depression
> detected by the onboard camera," said the paper's lead author, Luciano Iess
> of Sapienza University of Rome. "Hence the conclusion that there must be a
> denser material at depth that compensates the missing mass: very likely
> liquid water, which is seven percent denser than ice. The magnitude of the
> anomaly gave us the size of the water reservoir."
> There is no certainty the subsurface ocean supplies the water plume spraying
> out of surface fractures near the south pole of Enceladus, however,
> scientists reason it is a real possibility. The fractures may lead down to a
> part of the moon that is tidally heated by the moon's repeated flexing, as it
> follows an eccentric orbit around Saturn.
> Much of the excitement about the Cassini mission's discovery of the Enceladus
> water plume stems from the possibility that it originates from a wet
> environment that could be a favorable environment for microbial life.
> "Material from Enceladus' south polar jets contains salty water and organic
> molecules, the basic chemical ingredients for life," said Linda Spilker,
> Cassini's project scientist at JPL. "Their discovery expanded our view of the
> 'habitable zone' within our solar system and in planetary systems of other
> stars. This new validation that an ocean of water underlies the jets furthers
> understanding about this intriguing environment."
> The Cassini-Huygens mission is a cooperative project of NASA, the European
> Space Agency and the Italian Space Agency. JPL manages the mission for NASA's
> Science Mission Directorate in Washington. For more information about
> Cassini, visit:
> Dwayne Brown
> Headquarters, Washington
> dwayne.c.brown at nasa.gov
> Jane Platt
> Jet Propulsion Laboratory, Pasadena, Calif.
> jane.platt at jpl.nasa.gov
> Brian Bell
> California Institute of Technology, Pasadena
> bpbell at caltech.edu
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Received on Thu 03 Apr 2014 04:12:23 PM PDT