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

Another Great Image: Tethys 'Eyes' Saturn

 

My first thought when seeing the image was the earlier Star Wars film where the Death Star was rounding a targeted planet.  However, this shot was taken from the Cassini spacecraft and shows the moon of Tethys.  Here is the rest of the story from NASA's Jet Propulsion Laboratory:

The two large craters on Tethys, near the line where day fades to night, almost resemble two giant eyes observing Saturn.

The location of these craters on Tethys’ terminator throws their topography into sharp relief. Both are large craters, but the larger and southernmost of the two shows a more complex structure. The angle of the lighting highlights a central peak in this crater. Central peaks are the result of the surface reacting to the violent post-impact excavation of the crater. The northern crater does not show a similar feature. Possibly the impact was too small to form a central peak, or the composition of the material in the immediate vicinity couldn’t support the formation of a central peak.

In this image Tethys is significantly closer to the camera, while the planet is in the background. Yet the moon is still utterly dwarfed by the giant Saturn.

This view looks toward the anti-Saturn side of Tethys. North on Tethys is up and rotated 42 degrees to the right. The image was taken in visible light with the Cassini spacecraft wide-angle camera on April 11, 2015.

The view was obtained at a distance of approximately 75,000 miles (120,000 kilometers) from Tethys. Image scale at Tethys is 4 miles (7 kilometers) per pixel.

And let's not forget Mimas, another moon of Saturn, that has even greater resemblance to the Death Star up close. 

First Helicopters Exploring Planets, And Now Submarines!

Recently I wrote about plans to use a helicopter on Mars to assist the rover.  Well, NASA is thinking beyond land and air, and it is now considering the seas.  The proposed target would be the methane seas of Saturn's moon Titan.  Here is a video from earlier this month showing how it would work.  It appears that the video captured the media's attention, though NASA was talking about this new approach in June of last year, stating:

We propose to develop a conceptual design of a submersible autonomous vehicle (submarine) to explore extraterrestrial seas. Specifically, to send a submarine to Titan’s largest northern sea, Kraken Mare. This craft will autonomously carry out detailed scientific investigations under the surface of Kraken Mare, providing unprecedented knowledge of an extraterrestrial sea and expanding NASA’s existing capabilities in planetary exploration to include in situ nautical operations. Sprawling over some 1000 km, with depths estimated at 300 m, Kraken Mare is comparable in size to the Great Lakes and represents an opportunity for an unprecedented planetary exploration mission.

The approach makes perfect sense given the destination in mind. And as with helicopters, it adds a fascinating dimension to our robotic travels.  I wonder what else NASA has up its sleeves. 

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

Great Image: Moon and Saturn Occultation

 

The composite image above shows the Moon Saturn Occultation from May 14th.  Created by amateur astronomer Paul Steward (see more of his work here), it was highlighted by Phil Plait in his Slate magazine column:

While these two tracks cross each other, it’s relatively rare for the Moon and Saturn to be at the same place at the same time. But it does happen, and it’s called an occultation. The Moon slowly covers Saturn, blocking it for some time, then once again moves out of the way to reveal the ringed planet. In this case, the timing of the May 14 occultation made it visible only for observers in the southern hemisphere, specifically Australia and New Zealand.

Image Credit:  Paul Steward, New Zeland

Bing Brings you Saturn

Today's homepage image on Bing was an image of Saturn taken by the Cassini probe.  I cannot remember the last time Bing highlighted an astronomy issue like this (though I am sure it happens and I just missed it).  Here is the story that goes along with today's image:

The sixth planet in our solar system, Saturn, with its distinctive rings, is probably the most recognizable planet after Earth—at least to us Earthlings. A NASA spacecraft called Cassini-Huygens took this photo. The craft’s sole mission was to fly directly to Saturn and then explore the planet as well as its rings and moons.

A recent discovery on one of Saturn’s smaller moons, Enceladus, has scientists clamoring for more information. Data collected by Cassini-Huygens has revealed a body of water, probably about the size of Lake Superior, below the moon’s surface. The discovery of water has suddenly made Enceladus a prime target in the search for life beyond Earth, since water is the basis for all life as we know it.

That discovery may prompt scientists to launch an additional satellite to Saturn, but it would be years before data would reach Earth. Saturn’s far away. Really far away. About 745 million miles away when Earth and Saturn are at their closest. Okay, that doesn’t mean anything to us, either, but consider, for example, that Cassini-Huygens launched in 1997, but didn’t enter Saturn’s orbit until 2004. We could be waiting awhile before learning if we have neighbors in the solar system.

Image Credit per Bing: NASA/JPL-Caltech/SSI

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.