Author Topic: NASA - Cassini updates  (Read 220187 times)

Offline eeergo

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Re: NASA - Cassini updates
« Reply #60 on: 10/13/2008 06:38 PM »
Thanks for the link, Jacques!

The images available are really mesmerizing:





Now if someone could figure out why on Earth (on Saturn, more appropriately) that stable, huge hexagon is there...
-DaviD-

Offline Eerie

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Re: NASA - Cassini updates
« Reply #61 on: 10/13/2008 08:43 PM »
I think it is figured out already. It`s not a hexagon, but six stable waves on a circle.

Offline eeergo

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Re: NASA - Cassini updates
« Reply #62 on: 10/13/2008 09:19 PM »
I wasn't aware of the explanation, but your post made me find some interesting references. Indeed, although not completely understood, it seems the phenomenon is not so bizarre as it may appear at first sight.

Some enlightening sources I've found. The most graphical explanation, a team that managed to create polygonal vortices, rotating at different speeds from the surrounding medium:
Article: http://www.physorg.com/news66924222.html
Main site: http://dcwww.fys.dtu.dk/~tbohr/RotatingPolygon/
Some similar phenomena appears to take place on Earth too:
http://www.math.nyu.edu/caos_teaching/hurricanes/BAMS_KosSch.pdf
Interesting discussion about this effect:
http://www.freelists.org/archives/sac-forum/04-2007/msg00001.html
-DaviD-

Online mike robel

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Re: NASA - Cassini updates
« Reply #63 on: 10/14/2008 12:37 AM »
As I think I read in a Jerry Pournelle Book, <yawn> "just another spectacular view and puzzle of Saturn."  :)

Offline jacqmans

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Re: NASA - Cassini updates
« Reply #64 on: 12/16/2008 01:58 PM »
RELEASE: 08-325

SATURN'S DYNAMIC MOON ENCELADUS SHOWS MORE SIGNS OF ACTIVITY

SAN FRANCISCO -- The closer scientists look at Saturn's small moon
Enceladus, the more they find evidence of an active world. The most
recent flybys of Enceladus made by NASA's Cassini spacecraft have
provided new signs of ongoing changes on and around the moon. The
latest high-resolution images of Enceladus show signs that the south
polar surface changes over time.

Close views of the southern polar region, where jets of water vapor
and icy particles spew from vents within the moon's distinctive
"tiger stripe" fractures, provide surprising evidence of Earth-like
tectonics. They yield new insight into what may be happening within
the fractures. The latest data on the plume -- the huge cloud of
vapor and particles fed by the jets that extend into space -- show it
varies over time and has a far-reaching effect on Saturn's
magnetosphere.

"Of all the geologic provinces in the Saturn system that Cassini has
explored, none has been more thrilling or carries greater
implications than the region at the southernmost portion of
Enceladus," said panel member Carolyn Porco, Cassini imaging team
leader at the Space Science Institute in Boulder, Colo.

A panel of Cassini scientists presented these new findings Monday in a
news briefing at the American Geophysical Union's Fall Meeting in San
Francisco.

"Enceladus has Earth-like spreading of the icy crust, but with an
exotic difference -- the spreading is almost all in one direction,
like a conveyor belt," said panelist Paul Helfenstein, Cassini
imaging associate at Cornell University in Ithaca, N.Y. "Asymmetric
spreading like this is unusual on Earth and not well understood."

"Enceladus has asymmetric spreading on steroids," Helfenstein added.
"We are not certain about the geological mechanisms that control the
spreading, but we see patterns of divergence and mountain-building
similar to what we see on Earth, which suggests that subsurface heat
and convection are involved."

The tiger stripes are analogous to the mid-ocean ridges on Earth's
seafloor where volcanic material wells up and creates new crust.
Using Cassini-based digital maps of the moon's south polar region,
Helfenstein reconstructed a possible history of the tiger stripes by
working backward in time and progressively snipping away older and
older sections of the map, each time finding that the remaining
sections fit together like puzzle pieces.

Images from recent close flybys also have bolstered an idea the
Cassini imaging team has that condensation from the jets erupting
from the surface may create ice plugs that close off old vents and
force new vents to open. The opening and clogging of vents also
corresponds with measurements indicating the plume varies from month
to month and year to year.

"We see no obvious distinguishing markings on the surface in the
immediate vicinity of each jet source, which suggests that the vents
may open and close and thus migrate up and down the fractures over
time," Porco said. "Over time, the particles that rain down onto the
surface from the jets may form a continuous blanket of snow along a
fracture."

Enceladus' output of ice and vapor dramatically impacts the entire
Saturnian system by supplying the ring system with fresh material and
loading ionized gas from water vapor into Saturn's magnetosphere.

"The ions added to the magnetosphere are spun up from Enceladus'
orbital speed to the rotational speed of Saturn," said Cassini
magnetometer science team member Christopher Russell of the
University of California, Los Angeles. "The more material is added by
the plume, the harder this is for Saturn to do, and the longer it
takes to accelerate the new material."

With water vapor, organic compounds and excess heat emerging from
Enceladus' south polar terrain, scientists are intrigued by the
possibility of a liquid-water-rich habitable zone beneath the moon's
south pole.

Cassini's flybys on Aug. 11 and Oct. 31 targeted Enceladus' fractured
southern region. An Oct. 9 flyby took the spacecraft deep into the
plume of water vapor and ice shooting out of the moon's vents.
Cassini's next flyby of Enceladus will be in November 2009. The
Cassini-Huygens mission is a cooperative project of NASA, the
European Space Agency and the Italian Space Agency.

For more information about the Cassini-Huygens mission, visit:

http://www.nasa.gov/cassini

Offline jacqmans

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Re: NASA - Cassini updates
« Reply #65 on: 12/16/2008 01:59 PM »
News release: 2008-237                                Dec. 15, 2008

Titan's Volcanoes Give NASA Spacecraft Chilly Reception

PASADENA, Calif. -- Data collected during several recent flybys of Titan by NASA's Cassini spacecraft have put another arrow in the quiver of scientists who think the Saturnian moon contains active cryovolcanoes spewing a super-chilled liquid into its atmosphere. The information was released today during a meeting of the American Geophysical Union in San Francisco, Calif.

"Cryovolcanoes are some of the most intriguing features in the solar system," said Rosaly Lopes, a Cassini radar team investigation scientist from NASA's Jet Propulsion Laboratory in Pasadena, Calif. "To put them in perspective -- if Mount Vesuvius had been a cryovolcano, its lava would have frozen the residents of Pompeii."

Rather than erupting molten rock, it is theorized that the cryovolcanoes of Titan would erupt volatiles such as water, ammonia and methane. Scientists have suspected cryovolcanoes might inhabit Titan, and the Cassini mission has collected data on several previous passes of the moon that suggest their existence. Imagery of the moon has included a suspect haze hovering over flow-like surface formations. Scientists point to these as signs of cryovolcanism there.

"Cassini data have raised the possibility that Titan's surface is active," said Jonathan Lunine, a Cassini interdisciplinary scientist from the Lunar and Planetary Laboratory, University of Arizona, Tucson. "This is based on evidence that changes have occurred on the surface of Titan, between flybys of Cassini, in regions where radar images suggest a kind of volcanism has taken place."

What led some Cassini scientists to believe that things are happening now were changes in brightness and reflectance detected at two separate and distinct regions of Titan. Reflectance is the ratio of light that radiates onto a surface to the amount reflected back. These changes were documented by Visible and Infrared Mapping Spectrometer data collected on Titan flybys from July 2004 to March 2006. In one of the two regions, the reflectance of the surface surged upward and remained higher than expected. In the other region, the reflectance shot up but then trended downward. There is also evidence that ammonia frost is present at one of the two changing sites. The ammonia was evident only at times when the region was inferred to be active.

"Ammonia is widely believed to be present only beneath the surface of Titan," said Robert M. Nelson of JPL, a scientist for Cassini's Visual and Infrared Mapping Spectrometer team. "The fact that we found it appearing at times when the surface brightened strongly suggests that material was being transported from Titan's interior to its surface."

Some Cassini scientists indicate that such volcanism could release methane from Titan's interior, which explains Titan's seemingly continuous supply of fresh methane. Without replenishment, scientists say, Titan's original atmospheric methane should have been exhausted long ago.

But other scientists familiar with the spectrometer data argue that the ammonia identification is not certain, and that the purported brightness changes might not be associated with changes on Titan's surface. Instead they might result from the transient appearances of ground "fogs" of ethane droplets very near Titan's surface, driven by atmospheric rather than geophysical processes. Nelson has considered the ground fog option, stating, "There remains the possibility that the effect is caused by a local fog, but if so, we would expect it to change in size over time due to wind activity, which is not what we see."

The chilly volcanoes of Titan are not a fait accompli. An alternative hypothesis to an active Titan suggests the Saturnian moon could be taking its landform evolution cues from a moon of Jupiter.

"Like Callisto, Titan may have formed as a relatively cold body, and may have never undergone enough tidal heating for volcanism to occur," said Jeffrey Moore, a planetary geologist at the NASA Ames Research Center, Moffett Field, Calif. "The flow-like features we see on the surface may just be icy debris that has been lubricated by methane rain and transported downslope into sinuous piles like mudflows."     

More revelations may be forthcoming. Scientists are still analyzing the data from Cassini's most recent flyby on Dec. 5. Cassini's next Titan flyby is scheduled in 11 days, when the spacecraft will come within 970 kilometers (603 miles) of its cloud-shrouded surface.

For more information about the Cassini-Huygens mission, visit: http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini .

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate in Washington, D.C.

The Cassini orbiter was designed, developed and assembled at JPL. The radar instrument was built by JPL and the Italian Space Agency, working with team members from the United States and several European countries. The Visual and Infrared Mapping Spectrometer team is based at the University of Arizona.


Offline toddbronco2

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Re: NASA - Cassini updates
« Reply #66 on: 02/23/2009 02:48 AM »
I haven't seen much interest from NSF toward Cassini, but the spacecraft is preparing for one of the more significant mechanical changes of the last several years with a switch to the backup B-branch thrusters, a move needed with the possibly imminent failure of one or two of the Reaction Control thrusters. Hopefully all will go well

Offline iamlucky13

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Re: NASA - Cassini updates
« Reply #67 on: 02/23/2009 05:07 AM »
Yeah, the unmanned mission definitely don't get nearly as much attention, especially when all is running smoothly. It doesn't sound like there's any expectations of problems, fortunately.

Offline rdale

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Re: NASA - Cassini updates
« Reply #68 on: 02/23/2009 07:33 AM »
Thanks for the update - the unmanned stuff is covered much more thoroughly at http://www.unmannedspaceflight.com/

Offline madscientist197

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Re: NASA - Cassini updates
« Reply #69 on: 02/25/2009 07:57 AM »
Yeah, that's a really incredible forum -- it's so highly moderated though, I'm always a bit afraid to post!
John

Offline Analyst

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Re: NASA - Cassini updates
« Reply #70 on: 02/26/2009 05:58 PM »
Yeah, that's a really incredible forum -- it's so highly moderated though, I'm always a bit afraid to post!

You can always leave after posting there, as I did.

Back to topic: The now proposed second mission extension will give us a total of 11 years in Saturnian orbit, hundreds of orbits, more than 100 Titan encounters, dozens of icy satellite encounters ... Talk about bang for the buck, or ROI, here it is.

Analyst
« Last Edit: 02/26/2009 06:07 PM by Analyst »

Offline jacqmans

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Re: NASA - Cassini updates
« Reply #71 on: 02/27/2009 04:36 PM »
Image advisory: 2009-032                                                     Feb. 26, 2009


Cassini Maps Global Pattern of Titan's Dunes

Titan's vast dune fields, which may act like weather vanes to determine general wind direction on Saturn's biggest moon, have been mapped by scientists who compiled four years of radar data collected by the Cassini spacecraft. 

Titan's rippled dunes are generally oriented east-west. Surprisingly, their orientation and characteristics indicate that near the surface, Titan's winds blow toward the east instead of toward the west. This means that Titan's surface winds blow opposite the direction suggested by previous global circulation models of Titan. 

"At Titan there are very few clouds, so determining which way the wind blows is not an easy thing, but by tracking the direction in which Titan's sand dunes form, we get some insight into the global wind pattern," says Ralph Lorenz, Cassini radar scientist at Johns Hopkins University Applied Physics Laboratory in Laurel, Md. "Think of the dunes sort of like a weather vane, pointing us to the direction the winds are blowing." A paper based on these findings appeared in the Feb. 11 issue of Geophysical Research Letters. 

"Titan's dunes are young, dynamic features that interact with topographic obstacles and give us clues about the wind regimes," said Jani Radebaugh, Brigham Young University, Provo,

Utah. "Winds come at these dunes from at least a couple of different directions, but then combine to create the overall dune orientation."

The new map, based on all the high-resolution radar data collected during a four-year period, is now available at: http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini .

The wind pattern is important for planning future Titan explorations that might involve balloon-borne experiments.

Some 16,000 dune segments were mapped out from about 20 radar images, digitized and combined to produce the new map.

Titan's dunes are believed to be made up of hydrocarbon sand grains likely derived from organic chemicals in Titan's smoggy skies. The dunes wrap around high terrain, which provides some idea of their height. They accumulate near the equator, and may pile up there because drier conditions allow for easy transport of the particles by the wind. Titan's higher latitudes contain lakes and may be "wetter" with more liquid hydrocarbons, not ideal conditions for creating dunes. 

Cassini, which launched in 1997 and is now in extended mission operations, continues to blaze its trail around the Saturn system and will visit Titan again on March 27. Seventeen Titan flybys are planned this year. 

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL manages the Cassini-Huygens mission for NASA's Science Mission Directorate. The Cassini orbiter was designed, developed and assembled at JPL. The radar instrument was built by JPL and the Italian Space Agency, working with team members from the United States and several European countries.

                                                                    -end-

Offline MBK004

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Re: NASA - Cassini updates
« Reply #72 on: 03/04/2009 07:26 AM »
http://www.nasa.gov/mission_pages/cassini/media/cassini-20090303.html
Image advisory: 2009-035
March 3, 2009

Newfound Moon May Be Source of Outer Saturn Ring
 
Cassini imaging scientists analyzing images acquired over the course of about 600 days found the tiny moonlet, half a kilometer (about a third of a mile) across, embedded within a partial ring, or ring arc, previously found by Cassini in Saturn's tenuous G ring.

The finding is being announced today in an International Astronomical Union circular. Images can be found at http://www.nasa.gov/cassini, http://saturn.jpl.nasa.gov and http://ciclops.org .

"Before Cassini, the G ring was the only dusty ring that was not clearly associated with a known moon, which made it odd," said Matthew Hedman, a Cassini imaging team associate at Cornell University in Ithaca, N.Y. "The discovery of this moonlet, together with other Cassini data, should help us make sense of this previously mysterious ring."

Saturn's rings were named in the order they were discovered. Working outward they are: D, C, B, A, F, G and E. The G ring is one of the outer diffuse rings. Within the faint G ring there is a relatively bright and narrow, 250-kilometer-wide (150-miles) arc of ring material, which extends 150,000 kilometers (90,000 miles), or one-sixth of the way around the ring's circumference. The moonlet moves within this ring arc. Previous Cassini plasma and dust measurements indicated that this partial ring may be produced from relatively large, icy particles embedded within the arc, such as this moonlet.

Scientists imaged the moonlet on Aug. 15, 2008, and then they confirmed its presence by finding it in two earlier images. They have since seen the moonlet on multiple occasions, most recently on Feb. 20, 2009. The moonlet is too small to be resolved by Cassini's cameras, so its size cannot be measured directly. However, Cassini scientists estimated the moonlet's size by comparing its brightness to another small Saturnian moon, Pallene.

Hedman and his collaborators also have found that the moonlet's orbit is being disturbed by the larger, nearby moon Mimas, which is responsible for keeping the ring arc together.

This brings the number of Saturnian ring arcs with embedded moonlets found by Cassini to three. The new moonlet may not be alone in the G ring arc. Previous measurements with other Cassini instruments implied the existence of a population of particles, possibly ranging in size from 1 to 100 meters (about three to several hundred feet) across. "Meteoroid impacts into, and collisions among, these bodies and the moonlet could liberate dust to form the arc," said Hedman.

Carl Murray, a Cassini imaging team member and professor at Queen Mary, University of London, said, "The moon's discovery and the disturbance of its trajectory by the neighboring moon Mimas highlight the close association between moons and rings that we see throughout the Saturn system. Hopefully, we will learn in the future more about how such arcs form and interact with their parent bodies."

Early next year, Cassini's camera will take a closer look at the arc and the moonlet. The Cassini Equinox mission, an extension of the original four-year mission, is expected to continue until fall of 2010.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory (JPL), a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.
« Last Edit: 03/04/2009 07:27 AM by MBK004 »

Offline jimvela

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Re: NASA - Cassini updates
« Reply #73 on: 03/04/2009 08:25 PM »
I have to wonder if the moonlet is the source of the ring, or if we're seeing a ring coalesce into a moon...  The ring systems are very interesting places indeed.

Offline jacqmans

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Re: NASA - Cassini updates
« Reply #74 on: 03/12/2009 03:26 PM »
STATUS REPORT: 2009-047                                                                       March 12, 2009

Cassini-Huygens Mission Status Report       

Cassini Swaps Thrusters

PASADENA, Calif. Early this morning the Cassini spacecraft relayed information that it had successfully swapped to a backup set of propulsion thrusters late Wednesday.

The swap was performed because of degradation in the performance of the primary thrusters, which had been in use since Cassini's launch in 1997. This is only the second time in Cassini's 11 years of flight that the engineering teams have gone to a backup system.

The thrusters are used for making small corrections to the spacecraft's course, for some attitude control functions, and for making angular momentum adjustments in the reaction wheels, which also are used for attitude control. The redundant set is an identical set of eight thrusters. Almost all Cassini engineering subsystems have redundant backup capability.

Cassini has successfully completed its original four-year planned tour of Saturn and is now in extended mission operations.

More information on the mission is available at: http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini .


Offline jacqmans

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Re: NASA - Cassini updates
« Reply #75 on: 03/24/2009 05:30 PM »
IMAGE ADVISORY: 2009-058                                         March 24, 2009                                   

Cassini Provides Virtual Flyover of Saturn's Moon Titan

PASADENA, Calif. "Fly me to the moon"--to Saturn's moon Titan, that is. New Titan movies and images are providing a bird's-eye view of the moon's Earth-like landscapes.

The new flyover maps show, for the first time, the 3-D topography and height of the 1,200-meter (4,000-foot) mountain tops, the north polar lake country, the vast dunes more than 100 meters (300 feet) high that crisscross the moon, and the thick flows that may have oozed from possible ice volcanoes.

The topographic maps were made from stereo pairs of radar images. They are available at: http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini .

Cassini radar team member Randy Kirk with the Astrogeology Science Center at the U.S. Geological Survey in Flagstaff, Ariz., created the maps. He used some of the 20 or so areas where two or more overlapping radar measurements were obtained during 19 Titan flybys. These stereo overlaps cover close to two percent of Titan's surface. The process of making topographic maps from them is just beginning, but the results already reveal some of the diversity of Titan's geologic features.

"These flyovers let you take in the bird's-eye sweeping views of Titan, the next best thing to being there," said Kirk. "We've mapped many kinds of features, and some of them remind me of Earth. Big seas, small lakes, rivers, dry river channels, mountains and sand dunes with hills poking out of them, lava flows."

Kirk will present these results today at the Lunar and Planetary Science Conference in The Woodlands, Texas.

High and low features are shown in unprecedented detail at about 2.4-kilometer (1.5-mile) resolution.  The maps show some features that may be volcanic flows.  These flows meander across a shallow basin in the mountains.  One area suspected to be an ice volcano, Ganesa Macula, does not appear to be a volcanic dome.  It may still have originated as a volcano, but it's too soon to know for sure.  "It could be a volcanic feature, a crater, or something else that has just been heavily eroded," added Kirk.

The stereo coverage includes a large portion of Titan's north polar lakes of liquid ethane and methane. Based on these topographical models, scientists are better able to determine the depth of lakes. The highest areas surrounding the lakes are some 1,200 meters (about 4,000 feet) above the shoreline. By comparing terrain around Earth to the Titan lakes, scientists estimate their depth is likely about 100 meters (300 feet) or less.

More 3-D mapping of these lakes will help refine these depth estimates and determine the volume of liquid hydrocarbons that exist on Titan. This information is important because these liquids evaporate and create Titan's atmosphere. Understanding this methane cycle can provide clues to Titan's weather and climate.

Launched in 1997, Cassini completed its primary four-year mission in 2008 and is now in extended mission operations, which run through September 2010. Over the course of the mission, Cassini plans to map more than three percent of Titan's surface in 3-D. About 38 percent of Titan's surface has been mapped with radar so far. On March 27, Cassini will complete its 52nd targeted flyby of Titan.   

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL manages the Cassini-Huygens mission for NASA's Science Mission Directorate. The Cassini orbiter was designed, developed and assembled at JPL. The radar instrument was built by JPL and the Italian Space Agency, working with team members from the United States and several European countries.


Offline jacqmans

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Re: NASA - Cassini updates
« Reply #76 on: 06/03/2009 07:51 PM »
IMAGE ADVISORY: 2009-093                                                         June 3, 2009             

Cassini Finds Titan's Clouds Hang on to Summer

Cloud chasers studying Saturn's moon Titan say its clouds form and move much like those on Earth, but in a much slower, more lingering fashion.

Their forecast for Titan's early autumn -- warm and wetter.

Scientists with NASA's Cassini mission have monitored Titan's atmosphere for three-and-a-half years, between July 2004 and December 2007, and observed more than 200 clouds. They found that the way these clouds are distributed around Titan matches scientists' global circulation models. The only exception is timing -- clouds are still noticeable in the southern hemisphere while fall is approaching.

"Titan's clouds don't move with the seasons exactly as we expected," said Sebastien Rodriguez of the University of Paris Diderot, in collaboration with Cassini visual and infrared mapping spectrometer team members at the University of Nantes, France. "We see lots of clouds during the summer in the southern hemisphere, and this summer weather seems to last into the early fall. It looks like Indian summer on Earth, even if the mechanisms are radically different on Titan from those on Earth. Titan may then experience a warmer and wetter early autumn than forecasted by the models."

On Earth, abnormally warm, dry weather periods in late autumn occur when low-pressure systems are blocked in the winter hemisphere. By contrast, scientists think the sluggishness of temperature changes at the surface and low atmosphere on Titan may be responsible for its unexpected warm and wet, hence cloudy, late summer.

The new infrared images showing the global cloud pattern are now available at: http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini .

As summer changes to fall at the equinox in August 2009, Titan's clouds are expected to disappear altogether. But, circulation models of Titan's weather and climate predict that clouds at the southern latitudes don't wait for the equinox and should have already faded out since 2005. However, Cassini was still able to see clouds at these places late in 2007, and some of them are particularly active at mid-latitudes and the equator.

Titan is the only moon in our solar system with a substantial atmosphere, and its climate shares Earth-like characteristics. Titan's dense, nitrogen-methane atmosphere responds much more slowly than Earth's atmosphere, as it receives about 100 times less sunlight because it is 10 times farther from the sun. Seasons on Titan last more than seven Earth years.

Scientists will continue to observe the long-term changes during Cassini's extended mission, which runs until the fall of 2010. Cassini is set to fly by Titan on May 5.


Offline jacqmans

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Re: NASA - Cassini updates
« Reply #77 on: 06/24/2009 06:10 PM »
European scientists on the joint NASA/ESA Cassini mission have detected, for the first time, sodium salts in ice grains of Saturn's E-ring, which is primarily replenished by material from the plumes of water vapour and ice grains emitted by Saturn’s moon Enceladus. The detection of salty ice indicates that the little moon harbours a reservoir of liquid water, perhaps even an ocean, beneath its surface.

More at:
http://www.esa.int/SPECIALS/Cassini-Huygens/SEMH0X0P0WF_0.html

Offline jacqmans

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Re: NASA - Cassini updates
« Reply #78 on: 06/24/2009 08:59 PM »
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


Offline ChrisGebhardt

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Re: NASA - Cassini updates
« Reply #79 on: 06/29/2009 11:57 PM »

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