Saturn's Moon Enceladus

And now onto another moon - Saturn's moon Enceladus. Just as we wonder about Pluto's changing surface and Charon's canyons, this moon is believed to have seas below the surface that could harbor life. The image above from the Cassini spacecraft provides a full view of the beautiful surface of this distant moon. 

NASA has more to say on this:

Do some surface features on Enceladus roll like a conveyor belt? A leading interpretation of images taken of Saturn's most explosive moon indicate that they do. This form of asymmetric tectonic activity, very unusual on Earth, likely holds clues to the internal structure of Enceladus, which may contain subsurface seas where life might be able to develop.  Pictured above is a composite of 28 images taken by the robotic Cassini spacecraft in 2008 just after swooping by the ice-spewing orb. Inspection of these images show clear tectonic displacements where large portions of the surface all appear to move all in one direction. On the image right appears one of the most prominent tectonic divides: Labtayt Sulci, a canyon about one kilometer deep. The small magnitude of Enceladus' wobble as it orbits Saturn might indicate damping by a globally extending underground ocean layer.

One possible mission being considered by NASA is called Enceladus Life Finder (ELF), which would entail a spacecraft flying through the moon's plume of surface material and returning the sample to Earth for further study.  An intriguing idea that will tell us much more about what is happening on the moon. 

Great Image: Dione and Saturn

The image above was taken last December by the Cassini spacecraft. The soft colors of Saturn are a strong contrast with the colorless moon. The European Space Agency provides more details on the photo:

The images used to create this view were obtained with the Cassini-Huygens wide-angle camera at a distance of approximately 603 000 kilometres from Dione through a filter sensitive to wavelengths of ultraviolet light.

Giovanni Domenico Cassini discovered Dione in 1684, it being one of the four moons he identified and named Sidera Lodoicea, or "the stars of Louis," to honor king Louis XIV.  A comparison of Dione to the Earth and its moon is shown below.

Image Credit: NASA/JPL/Space Science Institute

Great Image: Titan's Shining Seas

While exoplanets are the interest du jour, our own solar system continues to fascinate. Take Titan, Saturn's moon and the subject of numerous Cassini spacecraft observations as well as investigation by the Huygens probe 10 years ago.  The image above shows an artificially colors view of the moon's methane seas taken last summer (our summer, that is).  One more intriguing feature in the far reaches of our solar system that Cassini continues to monitor for our behalf.

Here is NASA's story concerning the image:

Why would the surface of Titan light up with a blinding flash? The reason: a sunglint from liquid seas. Saturn's moon Titan has numerous smooth lakes of methane that numerous passes of our Solar System's most mysterious moon, Cassini has revealed Titan to be a world with active weather -- including times when it rains a liquefied version of natural gas.

Image Credit: VIMS Team, Univerity of Arizona, ESA, NASA

Great Image: Titan and Saturn's Rings

With other things happening around the solar system, we can forget about the ongoing mission of NASA's Cassini spacecraft as it orbits Saturn.  After 10 years, we are still getting valuable information and images from this distant aircraft.  Here is NASA's story for this image:

When orbiting Saturn, be sure to watch for breathtaking superpositions of moons and rings. One such picturesque vista was visible recently to the robot Cassini spacecraft now orbiting Saturn. In 2006 April, Cassini captured Saturn's A and F rings stretching in front of cloud-shrouded Titan. Near the rings and appearing just above Titan was Epimetheus, a moon which orbits just outside the F ring. The dark space in the A ring is called the Encke Gap, although several thin knotted ringlets and even the small moon Pan orbit there.

Cassini celebrated its 10th year in orbit back in June, when NASA highlighted some of its discoveries over this period:

-- The Huygens probe makes first landing on a moon in the outer solar system (Titan)
-- Discovery of active, icy plumes on the Saturnian moon Enceladus
-- Saturn's rings revealed as active and dynamic -- a laboratory for how planets form
-- Titan revealed as an Earth-like world with rain, rivers, lakes and seas
-- Studies of Saturn's great northern storm of 2010-2011
-- Studies reveal radio-wave patterns are not tied to Saturn's interior rotation, as previously thought
-- Vertical structures in the rings imaged for the first time
-- Study of prebiotic chemistry on Titan
-- Mystery of the dual, bright-dark surface of the moon Iapetus solved
-- First complete view of the north polar hexagon and discovery of giant hurricanes at both of Saturn's poles

Visit the Cassini mission site for more on the spacecraft as well as additional images.

Top Image Credit: Cassini Imaging Team, ISS, JPL, ESA, NASA

Away from the Politics II: Discoveries in the Solar System

The past few weeks have been full of announcements on discoveries within our solar system.  Here are some of the highlights:

• Subsurface Lake on Enceladus:  NASA's Cassini probe has identified a reservoir of water on Saturn's moon (shown above in comparison to our own Moon) that is 19 to 25 miles thick, or equivalent to the water in one of the Great Lakes (I have read comparisons to either Lake Erie or Lake Superior).  What does this mean?  NASA stated: "The subsurface ocean evidence supports the inclusion of Enceladus among the most likely places in our solar system to host microbial life."  Interesting indeed.

• An Asteroid with Rings:  Rings were found around an asteroid named Chariklo, which orbits in the outer solar system between Saturn and Uranus.  Chariklo is one of the larger objects in that region being about 155 miles across. This is the first non-planetary body in our solar system we have identified with its own rings.

• New Icy Object Beyond the Kuiper Belt:  Astronomers have spotted a new object now labeled 2012VP113 (not very dramatic) that orbits outside the Kuiper Belt, which contains Pluto.  We already know that dwarf planet Sedna is out in those reaches.  This raises some interesting questions.  The Sydney Morning Herald reports this could indicate something is pulling these ice objects out that far, such as undiscovered giant planet or maybe a passing star from long ago. 

Great Images: Dione and Rhea

You might think you are watching daughter cells, as as one planet splits into two.  But what you really see are two of Saturn's moon, Dione and Rhea, passing your sight of vision in their orbits while still very far apart.  Here is the explanation from Discover Magazine:

...the top moon there is Dione, and the bottom one is Rhea. As Cassini flew by them, Dione was closer (a little more than 1.1 million km or about 690,000 miles), and Rhea farther away (1.6 million km or 1 million miles). The angle of Cassini’s trajectory was just right such that Dione passed right in front of Rhea, and it snapped this image just as it happened.

Great Images: Jupiter and Ganymede

This image is part of the NASA Planetary Photo Journal Collection and found at nasaimages.org. Here is the photo's accompanying text:

The solar system's largest moon, Ganymede, is captured here alongside the planet Jupiter in a color picture taken by NASA's Cassini spacecraft on Dec. 3, 2000.

Ganymede is larger than the planets Mercury and Pluto and Saturn's largest moon, Titan. Both Ganymede and Titan have greater surface area than the entire Eurasian continent on our planet. Cassini was 26.5 million kilometers (16.5 million miles) from Ganymede when this image was taken. The smallest visible features are about 160 kilometers (about 100 miles) across.

The bright area near the south (bottom) of Ganymede is Osiris, a large, relatively new crater surrounded by bright icy material ejected by the impact, which created it. Elsewhere, Ganymede displays dark terrains that NASA's Voyager and Galileo spacecraft have shown to be old and heavily cratered. The brighter terrains are younger and laced by grooves. Various kinds of grooved terrains have been seen on many icy moons in the solar system. These are believed to be the surface expressions of warm, pristine, water-rich materials that moved to the surface and froze.

Ganymede has proven to be a fascinating world, the only moon known to have a magnetosphere, or magnetic environment, produced by a convecting metal core. The interaction of Ganymede's and Jupiter's magnetospheres may produce dazzling variations in the auroral glows in Ganymede's tenuous atmosphere of oxygen.

Cassini is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini mission for NASA's Office of Space Science, Washington, D.C. 

Here is an earlier shot of Ganymede from NASA's Jet Propulsion Laboratory's Photojournal page:  

In this global view of Ganymede's trailing side, the colors are enhanced to emphasize color differences. The enhancement reveals frosty polar caps in addition to the two predominant terrains on Ganymede, bright, grooved terrain and older, dark furrowed areas. Many craters with diameters up to several dozen kilometers are visible. The violet hues at the poles may be the result of small particles of frost which would scatter more light at shorter wavelengths (the violet end of the spectrum). Ganymede's magnetic field, which was detected by the magnetometer on NASA's Galileo spacecraft in 1996, may be partly responsible for the appearance of the polar terrain. Compared to Earth's polar caps, Ganymede's polar terrain is relatively vast. The frost on Ganymede reaches latitudes as low as 40 degrees on average and 25 degrees at some locations. For comparison with Earth, Miami, Florida lies at 26 degrees north latitude, and Berlin, Germany is located at 52 degrees north.

North is to the top of the picture. The composite, which combines images taken with green, violet, and 1 micrometer filters, is centered at 306 degrees west longitude. The resolution is 9 kilometers (6 miles) per picture element. The images were taken on 29 March 1998 at a range of 918000 kilometers (570,000 miles) by the Solid State Imaging (SSI) system on NASA's Galileo spacecraft.

The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC.