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. Anot