Cassini and Saturn's moons - Page 20

Noclevername · #**571** (**permalink**) 24-May-2007, 10:18 PM

Quote:

Originally Posted by Jerry

Careful, this is not an established fact. The data-in hand (refractive index and such), are inconsistent with a surface of primarily water-ice. This is quite a contrast with Enceladus, where the surface is clearly water-ice, both in terms of the visual wavelength color, thermal emissivity, and the radar signature.

The surface of Titan is probably filthy, with wind-blown dust consisting primarily of hydrocarbons. Dirty, dirty ice!

Disinfo Agent · #**572** (**permalink**) 24-May-2007, 10:51 PM

That picture of the Titan sea in the previous page is so neat!

Kullat Nunu · #**573** (**permalink**) 13-June-2007, 11:03 PM

First close-up image of Atlas. The moon is saucer-shaped and we are seeing its southern hemisphere. Look at its equator! It has collected quite a lot of "snow" from the rings.

Kullat Nunu · #**574** (**permalink**) 13-June-2007, 11:29 PM

The Planetary Society Weblog: Funny Little Atlas

Includes a cleaned-up color version of the image and an older image where Atlas' saucer-like shape is prominently visible.

Disinfo Agent · #**575** (**permalink**) 13-September-2007, 03:57 PM

More cool pictures:

Titan's ring of twilight
Titan: Above Adiri
Titan's Giant North Pole Cloud
Rhea in saturnshine
Enceladus: icy emanations
Moons in the night
Prometheus makes contact

Spacemad · #**576** (**permalink**) 17-September-2007, 07:48 AM

Thanks for those links to the images - they were very good!

01101001 · #**577** (**permalink**) 21-September-2007, 06:39 PM

Anthe, Jarnsaxa, Greip, and Tarqeq are New names for some irregular Saturnian moons (Planetary Society Weblog).

Disinfo Agent · #**578** (**permalink**) 21-September-2007, 08:07 PM

Hey, who allowed them to trade the good old fashioned Greek pantheon for unpronounceable barbarian abominations?

parallaxicality · #**579** (**permalink**) 21-September-2007, 08:49 PM

There are only so many Greek names. Any more moons and we're gonna have to start naming them Dukakis and Stephanopoulos.

Launch window · #**580** (**permalink**) 08-October-2007, 01:53 PM

Quote:

Originally Posted by Disinfo Agent

More cool pictures:

Titan's ring of twilight
Titan: Above Adiri
Titan's Giant North Pole Cloud
Rhea in saturnshine
Enceladus: icy emanations
Moons in the night
Prometheus makes contact

Great images ! Thanks

That earlier Iapetus flyby had some great info

Kullat Nunu · #**581** (**permalink**) 08-October-2007, 09:01 PM

Press release images from the Iapetus flyby are here (provided the server responds).

They're also available at NASA's Planetary Photojournal.

ToSeek · #**582** (**permalink**) 11-October-2007, 09:41 PM

Cassini's new view of land of lakes and seas

Quote:

The best views of the hydrocarbon lakes and seas on Saturn's moon Titan taken by the Cassini spacecraft are being released today.
A new radar image comprised from seven Titan fly-bys over the last year and a half shows a north pole pitted with giant lakes and seas, at least one of them larger than Lake Superior in the USA, the largest freshwater lake on Earth. Approximately 60% of Titan's north polar region, above 60° north, has been mapped by Cassini's radar instrument. About 14% of the mapped region is covered by what scientists interpret as liquid hydrocarbon lakes.

"This is our version of mapping Alaska, the northern parts of Canada, Greenland, Scandinavia and Northern Russia," said Rosaly Lopes, Cassini radar scientist at the Jet Propulsion Laboratory, USA. "It is like mapping these regions of Earth for the first time."

01101001 · #**583** (**permalink**) 11-October-2007, 10:23 PM

Planetary Society Weblog: News flash: Lakes at Titan's south pole, too, on top of the land of lakes in the north

Quote:

This one RADAR swath hasn't answered that question yet, but what it has done is show that the features visible to RADAR near Titan's south pole look a lot like the features visible to RADAR near Titan's north pole. And that, in turn, suggests that, as on Earth climate (rather than internal geologic forces or external forces like impact cratering) plays a large role in the formation of Titan's polar surface features, since climate, averaged over the year, is one thing that will be the same in the north and south.

01101001 · #**584** (**permalink**) 25-October-2007, 06:40 AM

Cassini and Saturn's Moonlets?

New CU-Boulder Study Confirms First-Known Belt Of Moonlets In Saturn Rings

Quote:

A narrow belt harboring moonlets as large as football stadiums discovered in Saturn's outermost ring probably resulted when a larger moon was shattered by a wayward asteroid or comet eons ago, according to a University of Colorado at Boulder study.
[...]
The team calculated that there likely are thousands of moonlets ranging in size from semi-trailers to sports arenas embedded in the "A" ring's thin moonlet belt that circles the planet.
[...]
The moonlets may be the result of the break-up of a ring-moon similar to Pan -- Saturn's innermost 20-mile diameter moon -- that was smashed by a comet or meteor, the team concluded. The team calculated the mass of the unseen moonlets in the belt greater than 50 feet in diameter to arrive at the estimated size of the moon involved in the collision creating the belt.

(Related to March 2006 report of "propellor" minimoons in this article.)

Launch window · #**585** (**permalink**) 19-November-2007, 10:33 AM

Facing Dione
http://ciclops.org/view.php?id=3862

ToSeek · #**586** (**permalink**) 28-November-2007, 10:23 PM

Organic 'building blocks' discovered in Titan's atmosphere

Quote:

Scientists analysing data gathered by the Cassini spacecraft have confirmed the presence of heavy negative ions in the upper regions of Titan’s atmosphere. These particles may act as organic building blocks for even more complicated molecules and their discovery was completely unexpected because of the chemical composition of the atmosphere (which lacks oxygen and mainly consists of nitrogen and methane).

01101001 · #**587** (**permalink**) 12-January-2008, 09:45 PM

Planetary Photojournal: Epimetheus Revealed

Planetary Photojournal: Rough, Icy Mimas

Planetary Photojournal: Wisp-covered Rhea

Planetary Photojournal: [Titan's] Adiri in View

Planetary Photojournal: Dione's Fractured Face

ToSeek · #**588** (**permalink**) 01-February-2008, 04:22 PM

Map of Iapetus

Quote:

This global map of Iapetus was created using images taken during Cassini spacecraft flybys, with Voyager images filling in the poles.

ToSeek · #**589** (**permalink**) 08-February-2008, 02:21 AM

JPL press release:

Quote:

Scientists Study "Plumbing" in Plumes of Enceladus

Scientists on the Cassini mission have become out-of-this world "plumbers" as they try to piece together what's happening inside the "pipes" feeding the plumes of Saturn's moon Enceladus.

Enceladus is jetting out giant geysers three times the size of the moon, and now scientists are beginning to understand how the ice grains are created and how they might have formed. Knowing the process of how the plume forms and the path the water-ice particles have to travel is giving them an insight into what may be a liquid reservoir or lake lying just beneath the surface.

"Since Cassini discovered the water vapor geysers, we've all wondered where this water vapor and ice are coming from. Is it from an underground water reservoir or are there some other processes at work? Now, after looking at data from multiple instruments, we can say there probably is water beneath the surface of Enceladus," said Juergen Schmidt, team member on Cassini's Cosmic Dust Analyzer at the University of Potsdam, Germany. This study appears in the Feb. 7, 2008, issue of the journal Nature.

The large number of ice particles observed spewing from the geysers and the steady rate at which these particles are produced require high temperatures, close to the melting point of ice, possibly resulting in an internal lake. The lake would be similar to Earth’s Lake Vostok, beneath Antarctica, where liquid water exists locked in ice. The ice grains then condense in the vapor evaporating from the water, streaming through cracks in the ice crust to the surface.

The presence of liquid water inside Enceladus would have major implications for future astrobiology studies on the possibility of life on bodies in the outer solar system.

Scientists have studied the plume dynamics since 2005, collecting data from several Cassini remote sensing instruments and those that sample particles directly, like the Cosmic Dust Analyzer. They conclude that an internal lake at a temperature of about 273 Kelvin (32 degrees Fahrenheit) is the best way to account for the material jetting out of the geysers.

At these warm temperatures, liquid water, ice and water vapor mingle. The vapor escapes to the vacuum of space through cracks in Enceladus’ ice crust. When the gas expands, it cools and the ice grains that make up the visible part of the plumes condense from the vapor. Vapor in the plumes is clocked at roughly the same speed as a supersonic jet, about 300 to 500 meters per second, or about 650 to 1,100 miles per hour. However, most of the condensed ice particles fail to reach Enceladus’ escape velocity of 240 meters per second (536 miles per hour).

Pinball-like physics account for the slow speed of the particles. Shooting up through crooked cracks in the ice, the particles ricochet off the walls, losing speed, while the water vapor moves unimpeded up the crevasse. The vapor reboosts the frozen particles as they pinball off the walls, carrying them upward. Reaching nozzle-like openings at the surface, the faster-moving water vapor shoots high above Enceladus, becoming entrapped in Saturn’s magnetosphere. Most of the particles, which have lost energy through collisions in transit, fail to achieve escape velocity and fall back to Enceladus’ surface. Only about 10 percent escape Enceladus and form Saturn’s E-ring.

"Our model provides a simple concept to understand how particles form, their speed and how they behave as they make their way out into space. If vapor temperature is too low, then the gas density is too small to push the grains out and we would not see such large amounts of particles," said Schmidt. "Therefore, we believe that at the site of evaporation, we must have temperatures near the melting point of water."

Scientists say that particles seen in the plumes are too numerous to have started from processes described in one existing model that requires low temperatures, proposing that gases may be trapped inside ice crystals. Another model suggests that water ice, suddenly exposed to the vacuum of space, sublimes, or boils, directly into vapor without liquefying first. But this would mean there are short bursts of activity, rather than the steady production of particles. The new model of grains condensing in a vent that evaporates from a liquid body is consistent with a steady production of particles, ejected from a localized source.

This research provides fundamental knowledge about solar system bodies, in particular those that, like our home planet, are homes to oceans – environments where life might evolve.

The next Enceladus flyby is in March 2008. The spacecraft closest approach will be at a mere 50 kilometers (30 miles) from the surface and the altitude will increase to about 200 kilometers (124 miles) as the spacecraft passes through the plumes. Cassini will sample the plumes directly and find out more about their makeup.

More information on the Cassini-Huygens mission is available at: 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 Cassini mission for NASA's Science Mission Directorate, Washington, D.C. JPL designed, developed and assembled the Cassini orbiter.

01101001 · #**590** (**permalink**) 08-February-2008, 05:10 PM

Planetary Photojournal: [Titan] A World of Questions

Planetary Photojournal: Cracked-up Dione

Planetary Photojournal: Battered Dione

Planetary Photojournal: Trailing Rhea

Spacemad · #**591** (**permalink**) 15-February-2008, 10:53 PM

Great images, thanks for posting them!

01101001 · #**592** (**permalink**) 20-February-2008, 02:48 AM

Quote:

Originally Posted by ToSeek

Cassini shows the dark side of Saturn's moon Dione

In another nod to the distant past, more on Dione and other Saturn moons: ESA: Cassini finds mingling moons may share a dark past

Quote:

Despite the incredible diversity of Saturn’s icy moons, theirs is a story of great interaction. Some are pock-marked, some seemingly dirty, others pristine, one spongy, one two-faced, some still spewing with activity and some seeming to be captured from the far reaches of the solar system. Yet many of them have a common thread - black ‘stuff’ coating their surfaces.

“We are beginning to unravel the mysteries of these different and strange moons,” said Rosaly Lopes, Cassini scientist at NASA’s Jet Propulsion Laboratory (JPL), USA. She coordinated a special section of 14 papers about Saturn’s icy moons that appears in the February issue of the journal Icarus.
[...]
Roger Clark of the United States Geological Survey in Denver, USA goes further, saying, “We see the same spectral signature on all the moons that have coatings of dark material.”

3488 · #**593** (**permalink**) 21-February-2008, 01:19 AM

Map of Tethys February 2008.

Rays on Rhea.

Andrew Brown.

01101001 · #**594** (**permalink**) 21-February-2008, 01:42 AM

Emily Lakdawalla "wasted" a day making montages of Saturn's icy moons for the Planetary Society Weblog. You should check it out. Showing off Saturn's moons

Quote:

[...] I wanted to come up with a graphic for an overview of Saturn's moons, and I couldn't resist delving into the massive database of Cassini images to produce something new.
[...]
There you have it. Which one do you like best?

3488 · #**595** (**permalink**) 23-February-2008, 12:56 AM

Cassini Synthetic Radar Aperture Images of Titan showing evidence of cryovolcanism?

1). Ganesa Macula & surrounding area.

2). Ganesa Macula (180 KM across & 1.5 KM high), low broad dome with what appears to be a summit caldera & flows.

3). Flows to south east of Ganesa Macula, not looking too unlike the flows at Sobo Fluctus on Io.

4). Summit of Ganesa Macula.

5). Central portion of Circus Maximus.

6). Domes in centre of Circus Maximus.

7). What appears to be cryovolcanic hills.

Andrew Brown.

3488 · #**596** (**permalink**) 28-February-2008, 12:01 AM

Saturn moon Janus.

Image taken by Cassini on: Wednesday 20th February 2008, from 169,138 kilometres.

Below image I have worked on.

Andrew Brown.

Launch window · #**597** (**permalink**) 28-February-2008, 12:34 AM

Epimetheus fly-by looked great

3488 · #**598** (**permalink**) 28-February-2008, 02:07 PM

I agree.

The Epimetheus fly was very interesting, as this Janus one was. We now have good images of both of them.

This is quite nice too.

Dione (top) & Janus (below).

Titan weather.

Andrew Brown.

ToSeek · #**599** (**permalink**) 06-March-2008, 09:01 PM

JPL press release:

Quote:

NEWS RELEASE: 2008-039 March 6, 2008

Saturn's Moon Rhea Also May Have Rings

PASADENA, Calif. -- NASA's Cassini spacecraft has found evidence of material orbiting Rhea, Saturn's second largest moon. This is the first time rings may have been found around a moon.

A broad debris disk and at least one ring appear to have been detected by a suite of six instruments on Cassini specifically designed to study the atmospheres and particles around Saturn and its moons.

"Until now, only planets were known to have rings, but now Rhea seems to have some family ties to its ringed parent Saturn," said Geraint Jones, a Cassini scientist and lead author on a paper that appears in the March 7 issue of the journal Science. Jones began this work while at the Max Planck Institute for Solar System Research, Katlenburg-Lindau, Germany, and is now at the Mullard Space Science Laboratory, University College, London.
Rhea is roughly 1,500 kilometers (950 miles) in diameter. The apparent debris disk measures several thousand miles from end to end. The particles that make up the disk and any embedded rings probably range from the size of small pebbles to boulders. An additional dust cloud may extend up to 5,900 kilometers (3,000 miles) from the moon's center, almost eight times the radius of Rhea.

"Like finding planets around other stars, and moons around asteroids, these findings are opening a new field of rings around moons," said Norbert Krupp, a scientist with Cassini's Magnetospheric Imaging Instrument from the Max Planck Institute for Solar System Research.

Since the discovery, Cassini scientists have carried out numerical simulations to determine if Rhea can maintain rings. The models show that Rhea's gravity field, in combination with its orbit around Saturn, could allow rings that form to remain in place for a very long time.

The discovery was a result of a Cassini close flyby of Rhea in November 2005, when instruments on the spacecraft observed the environment around the moon. Three instruments sampled dust directly. The existence of some debris was expected because a rain of dust constantly hits Saturn's moons, including Rhea, knocking particles into space around them. Other instruments' observations showed how the moon was interacting with Saturn's magnetosphere, and ruled out the possibility of an atmosphere.
Evidence for a debris disk in addition to this tenuous dust cloud came from a gradual drop on either side of Rhea in the number of electrons detected by two of Cassini's instruments. Material near Rhea appeared to be shielding Cassini from the usual rain of electrons. Cassini's Magnetospheric Imaging Instrument detected sharp, brief drops in electrons on both sides of the moon, suggesting the presence of rings within the disk of debris. The rings of Uranus were found in a similar fashion, by NASA's Kuiper Airborne Observatory in 1977, when light from a star blinked on and off as it passed behind Uranus' rings.

"Seeing almost the same signatures on either side of Rhea was the clincher," added Jones. "After ruling out many other possibilities, we said these are most likely rings. No one was expecting rings around a moon."
One possible explanation for these rings is that they are remnants from an asteroid or comet collision in Rhea's distant past. Such a collision may have pitched large quantities of gas and solid particles around Rhea. Once the gas dissipated, all that remained were the ring particles. Other moons of Saturn, such as Mimas, show evidence of a catastrophic collision that almost tore the moon apart.

"The diversity in our solar system never fails to amaze us," said Candy Hansen, co-author and Cassini scientist on the Ultraviolet Imaging Spectrograph at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "Many years ago we thought Saturn was the only planet with rings. Now we may have a moon of Saturn that is a miniature version of its even more elaborately decorated parent."

These ring findings make Rhea a prime candidate for further study. Initial observations by the imaging team when Rhea was near the sun in the sky did not detect dust near the moon remotely. Additional observations are planned to look for the larger particles.

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 Cassini-Huygens mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter was designed, developed and assembled at JPL. The Magnetospheric Imaging Instrument was designed, built and is operated by an international team led by the Applied Physics Laboratory of the Johns Hopkins University, Laurel, Md.

For information on the Cassini mission, visit: http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov .

01101001 · #**600** (**permalink**) 06-March-2008, 09:08 PM

Cool. Maybe we'll need another topic: Cassini and Saturn's moons' rings

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