Posted on by Ken Kremer

2011: Top Stories from the Best Year Ever for NASA Planetary Science!

Dawn Orbiting Vesta. NASA's Dawn spacecraft achieved orbit at the giant asteroid Vesta in July 2011. The depiction of Vesta is based on images obtained by Dawn's framing cameras. Dawn is an international collaboration of the US, Germany and Italy. Credit: NASA/JPL-Caltech

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A year ago, 2011 was proclaimed as the “Year of the Solar System” by NASA’s Planetary Science division. And what a year of excitement it was indeed for the planetary science community, amateur astronomers and the general public alike !

NASA successfully delivered astounding results on all fronts – On the Story of How We Came to Be.

“2011 was definitely the best year ever for NASA Planetary Science!” said Jim Green in an exclusive interview with Universe Today. Green is the Director of Planetary Science for the Science Mission Directorate at NASA HQ. “The Search for Life is a significant priority for NASA.”

This past year was without doubt simply breathtaking in scope in terms of new missions, new discoveries and extraordinary technical achievements. The comprehensive list of celestial targets investigated in 2011 spanned virtually every type of object in our solar system – from the innermost planet to the outermost reaches nearly touching interplanetary space.

There was even a stunningly evocative picture showing “All of Humanity” – especially appropriate now in this Holiday season !

You and all of Humanity are here !
-- Earth & Moon Portrait by Juno from 6 Million miles away --
First Photo transmitted from Jupiter Bound Juno shows Earth (on the left) and the Moon (on the right). Taken on Aug. 26, 2011 when spacecraft was about 6 million miles (9.66 million kilometers) away from Earth. Credit: NASA/JPL-Caltech

Three brand new missions were launched and ongoing missions orbited a planet and an asteroid and flew past a comet.

“NASA has never had the pace of so many planetary launches in such a short time,” said Green.

And three missions here were awarded ‘Best of 2011’ for innovation !

Mars Science Laboratory (MSL), Dawn and MESSENGER named “Best of What’s New” in 2011 by Popular Science magazine. 3 NASA Planetary Science missions received the innovation award for 2011 from Popular Science magazine. Artist concept shows mosaic of MESSENGER, Mars Science Laboratory and Dawn missions. Credit: NASA/JPL-Caltech

Here’s the Top NASA Planetary Science Stories of 2011 – ‘The Year of the Solar System’ – in chronological order

1. Stardust-NExT Fly By of Comet Tempel 1

Starting from the first moments of 2011 at the dawn of Jan. 1, hopes were already running high for planetary scientists and engineers busily engaged in setting up a romantic celestial date in space between a volatile icy comet and an aging, thrusting probe on Valentine’s Day.

The comet chasing Stardust-Next spacecraft successfully zoomed past Comet Tempel 1 on Feb. 14 at 10.9 km/sec (24,000 MPH) after flying over 6 Billion kilometers (3.5 Billion mi).

6 Views of Comet Tempel 1 and Deep Impact crater during Stardust-NExT flyby on Feb. 14, 2011
Arrows show location of man-made crater created in 2005 by NASA’s prior Deep Impact comet mission and newly imaged as Stardust-NExT zoomed past comet in 2011. The images progress in time during closest approach to comet beginning at upper left and moving clockwise to lower left. Credit: NASA/JPL-Caltech/University of Maryland. Post process and annotations by Marco Di Lorenzo & Kenneth Kremer

The craft approached within 178 km (111mi) and snapped 72 astonishingly detailed high resolution science images over barely 8 minutes. It also fulfilled the teams highest hopes by photographing the human-made crater created on Tempel 1 in 2005 by a cosmic collision with a penetrator hurled by NASA’s Deep Impact spacecraft. The probe previously flew by Comet Wild 2 in 2004 and returned cometary coma particles to Earth in 2006

Tempel 1 is the first comet to be visited by two spaceships from Earth and provided the first-ever opportunity to compare observations on two successive passages around the Sun.

Don Brownlee, the original Principal Investigator, summarized the results for Universe Today; “A great bonus of the mission was the ability to flyby two comets and take images and measurements. The wonderfully successful flyby of Comet Tempel 1 was a great cap to the 12 year mission and provided a great deal of new information to study the diversity among comets.”

“The new images of Tempel showed features that form a link between seemingly disparate surface features of the 4 comets imaged by spacecraft. Combining data on the same comet from the Deep Impact and Stardust missions has provided important new insights in to how comet surfaces evolve over time and how they release gas and dust into space”.

2. MESSENGER at Mercury

On March 18, the Mercury Surface, Space Environment, Geochemistry, and Ranging, or MESSENGER, spacecraft became the first spacecraft inserted into orbit around Mercury, the innermost planet.

So far MESSENGER has completed 1 solar day – 176 Earth days- circling above Mercury. The probe has collected a treasure trove of new data from the seven instruments onboard yielding a scientific bonanza; these include global imagery of most of the surface, measurements of the planet’s surface chemical composition, topographic evidence for significant amounts of water ice, magnetic field and interactions with the solar wind.

“MESSENGER discovered that Mercury has an enormous core, larger than Earth’s. We are trying to understand why that is and why Mercury’s density is similar to Earth’s,” Jim Green explained to Universe Today.

The First Solar Day
After its first Mercury solar day (176 Earth days) in orbit, MESSENGER has nearly completed two of its main global imaging campaigns: a monochrome map at 250 m/pixel and an eight-color, 1-km/pixel color map. Small gaps will be filled in during the next solar day. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

“The primary mission lasts 2 solar days, equivalent to 4 Mercury years.”

“NASA has granted a 1 year mission extension, for a total of 8 Mercury years. This will allow the team to understand the environment at Mercury during Solar Maximum for the first time. All prior spacecraft observations were closer to solar minimum,” said Green.

MESSENGER was launched in 2004 and the goal is to produce the first global scientific observations of Mercury and piece together the puzzle of how Mercury fits in with the origin and evolution of our solar system.

NASA’s Mariner 10 was the only previous robotic probe to explore Mercury, during three flyby’s back in the mid-1970’s early in the space age.

3. Dawn Asteroid Orbiter

The Dawn spacecraft achieved orbit around the giant asteroid Vesta in July 2011 after a four year interplanetary cruise and began transmitting the history making first ever close-up observations of the mysteriously diverse and alien world that is nothing short of a ‘Space Spectacular’.

“We do not have a good analog to Vesta anywhere else in the Solar System,” Chris Russell said to Universe Today. Russell, from UCLA, is the scientific Principal Investigator for Dawn.

Before Dawn, Vesta was just another fuzzy blob in the most powerful telescopes. Dawn has completely unveiled Vesta as a remarkably dichotomous, heavily battered and pockmarked world that’s littered with thousands of craters, mountains and landslides and ringed by mystifying grooves and troughs. It will unlock details about the elemental abundances, chemical composition and interior structure of this marvelously intriguing body.

Cataclysmic collisions eons ago excavated Vesta so it lacks a south pole. Dawn discovered that what unexpectedly remains is an enormous mountain some 16 miles (25 kilometers) high, twice the height of Mt. Everest.

Dawn is now about midway through its 1 year mission at Vesta which ends in July 2012 with a departure for Ceres, the largest asteroid. So far the framing cameras have snapped more than 10,000 never-before-seen images.

“What can be more exciting than to explore an alien world that until recently was virtually unknown!. ” Dr. Marc Rayman said to Universe Today. Rayman is Dawn’s Chief Engineer from NASA’s Jet Propulsion Lab (JPL) in Pasadena, Calif.

“Dawn is NASA at its best: ambitious, exciting, innovative, and productive.”

4. Juno Jupiter Orbiter

The solar powered Juno spacecraft was launched on Aug. 5 at Cape Canaveral Air Force Station in Florida, to embark on a five year, 2.8 billion kilometer (1.7 Billion mi) trek to Jupiter, our solar system’s largest planet. It was the first of three NASA planetary science liftoffs scheduled in 2011.

Juno Jupiter Orbiter soars skyward to Jupiter on Aug. 5, 2011 from Cape Canaveral Air Force Station, Florida. Credit: Ken Kremer

Juno’s goal is to map to the depths of the planets interior and elucidate the ingredients of Jupiter’s genesis hidden deep inside. These measurements will help answer how Jupiter’s birth and evolution applies to the formation of the other eight planets.

The 4 ton spacecraft will arrive at the gas giant in July 2016 and fire its braking rockets to go into a polar orbit and circle the planet 33 times over about one year.

The suite of nine instruments will scan the gas giant to find out more about the planets origins, interior structure and atmosphere, measure the amount of water and ammonia, observe the aurora, map the intense magnetic field and search for the existence of a solid planetary core.

“Jupiter is the Rosetta Stone of our solar system,” said Scott Bolton, Juno’s principal investigator from the Southwest Research Institute in San Antonio. “It is by far the oldest planet, contains more material than all the other planets, asteroids and comets combined and carries deep inside it the story of not only the solar system but of us. Juno is going there as our emissary — to interpret what Jupiter has to say.”

5. Opportunity reaches Endeavour Crater on Mars

The long lived Opportunity rover finally arrived at the rim of the vast 14 mile (22 kilometer) wide Endeavour Crater in mid-August 2011 following an epic three year trek across treacherous dune fields – a feat once thought unimaginable. All told, Opportunity has driven more than 34 km ( 21 mi) since landing on the Red Planet way back in 2004 for a mere 90 sol mission.

Endeavour Crater Panorama from Opportunity Mars Rover in August 2011
Opportunity arrived at the rim of Endeavour on Sol 2681, August 9, 2011 after a three year trek. The robot photographed segments of the huge craters eroded rim in this panoramic vista. Endeavour Crater is 14 miles (22 kilometers) in diameter. Mosaic Credit: NASA/JPL/Cornell/Marco Di Lorenzo/Kenneth Kremer

In November, the rover discovered the most scientifically compelling evidence yet for the flow of liquid water on ancient Mars in the form of a water related mineral vein at a spot dubbed “Homestake” along an eroded ridge of Endeavour’s rim.

Read my story about the Homestake discovery here, along with our panoramic mosaic showing the location – created by Ken Kremer and Marco Di Lorenzo and published by Astronomy Picture of the Day (APOD) on 12 Dec. 2011.

Watch for my upcoming story detailing Opportunity’s accomplishments in 2011.

6. GRAIL Moon Mappers

The Gravity Recovery and Interior Laboratory, or GRAIL mission is comprised of twin spacecraft tasked to map the moon’s gravity and study the structure of the lunar interior from crust to core.

Twin GRAIL Probes GO for Lunar Orbit Insertion on New Year’s Eve and New Year’s Day
GRAIL spacecraft will map the moon's gravity field and interior composition. Credit: NASA/JPL-Caltech

The dynamic duo lifted off from Cape Canaveral on September 10, 2011 atop the last Delta II rocket that will likely soar to space from Florida. After a three month voyage of more than 2.5 million miles (4 million kilometers) since blastoff, the two mirror image GRAIL spacecraft dubbed Grail-A and GRAIL-B are sailing on a trajectory placing them on a course over the Moon’s south pole on New Year’s weekend.

Each spacecraft will fire the braking rockets for about 40 minutes for insertion into Lunar Orbit about 25 hours apart on New Year’s Eve and New Year’s Day.

Engineers will then gradually lower the satellites to a near-polar near-circular orbital altitude of about 34 miles (55 kilometers).

The spacecraft will fly in tandem and the 82 day science phase will begin in March 2012.

“GRAIL is a Journey to the Center of the Moon”, says Maria Zuber, GRAIL principal investigator from the Massachusetts Institute of Technology (MIT). “GRAIL will rewrite the book on the formation of the moon and the beginning of us.”

“By globally mapping the moon’s gravity field to high precision scientists can deduce information about the interior structure, density and composition of the lunar interior. We’ll evaluate whether there even is a solid or liquid core or a mixture and advance the understanding of the thermal evolution of the moon and the solar system,” explained co-investigator Sami Asmar to Universe Today. Asmar is from NASA’s Jet Propulsion Laboratory (JPL)

7. Curiosity Mars Rover

The Curiosity Mars Science Lab (MSL) rover soared skywards on Nov. 26, the last of 2011’s three planetary science missions. Curiosity is the newest, largest and most technologically sophisticated robotic surveyor that NASA has ever assembled.

“MSL packs the most bang for the buck yet sent to Mars.” John Grotzinger, the Mars Science Laboratory Project Scientist of the California Institute of Technology, told Universe Today.

The three meter long robot is the first astrobiology mission since the Viking landers in the 1970’s and specifically tasked to hunt for the ‘Ingredients of Life’ on Mars – the most Earth-like planet in our Solar System.


Video caption: Action packed animation depicts sequences of Curiosity departing Earth, the nail biting terror of the never before used entry, descent and landing on the Martian surface and then looking for signs of life at Gale Crater during her minimum two year expedition across hitherto unseen and unexplored Martian landscapes, mountains and craters. Credit: NASA

Curiosity will gather and analyze samples of Martian dirt in pursuit of the tell-tale signatures of life in the form of organic molecules – the carbon based building blocks of life as we know it.

NASA is targeting Curiosity to a pinpoint touch down inside the 154 km (96 mile) wide Gale Crater on Aug. 6, 2012. The crater exhibits exposures of phyllosilicates and other minerals that may have preserved evidence of ancient or extant Martian life and is dominated by a towering 3 mile (5 km) high mountain.

“10 science instruments are all aimed at a mountain whose stratigraphic layering records the major breakpoints in the history of Mars’ environments over likely hundreds of millions of years, including those that may have been habitable for life,” Grotzinger told me.

Titan Upfront
The colorful globe of Saturn's largest moon, Titan, passes in front of the planet and its rings in this true color snapshot from NASA's Cassini spacecraft. Credit: NASA/JPL-Caltech/Space Science Institute
Curiosity Mars Science Laboratory Rover and Ken Kremer - inside the Cleanroom at the Kennedy Space Center. Last View of Curiosity just prior to folding and encapsulation for launch. Credit: Ken Kremer

This past year Ken was incredibly fortunate to witness the ongoing efforts of many of these magnificent endeavors.

Posted on by Jason Major

Enceladus Gives Cassini Some Radar Love

New radar images from Encealdus' south pole show high amounts of surface texturing. NASA/JPL-Caltech/SSI.

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Cassini’s done it again! Soaring over Saturn’s moon Enceladus back on November 6, the spacecraft obtained the highest-resolution images yet of the moon’s south polar terrain, revealing surface details with visible, infrared and radar imaging that have never been seen before.

Of particular interest are new image swaths acquired by the spacecraft’s synthetic-aperture radar (SAR) instrument, which has never before been used on Enceladus. The radar, which is highly sensitive to surface textures, reveals some extremely bright regions that have surprised scientists.

Detail of the radar-imaged area (enlarged). NASA/JPL-Caltech/SSI.

“It’s puzzling why this is some of the brightest stuff Cassini has seen,” said Steve Wall, deputy team lead of Cassini’s radar team based at NASA’s Jet Propulsion Laboratory in Pasadena. “One possibility is that the area is studded with rounded ice rocks. But we can’t yet explain how that would happen.”

The SAR images did not focus on the moon’s now-famous “tiger stripe” fractures (called sulci) which are the sources of its icy jets. Instead, Cassini scanned areas a few hundred miles around the stripes. These regions have not been extensively imaged before and this new data shows surface patterns and elevations that had been previously unknown.

Some of the steep grooves in the imaged areas were shown to be as deep as 2,100 feet (650 m), and 1.2 miles (2 km) wide.

Cassini passed by the 318-mile (511-km) -wide moon at 04:49 UTC on November 6, 2011. Cassini’s radar instrument was built by JPL and the Italian Space Agency, working with team members from the U.S. and several European countries. Previously used to image the surface of Titan, which is hidden from view by a thick atmosphere, this is the first time the instrument was used on Enceladus.

Here’s a video from the imaging team below:

See the news release on the NASA mission page here, or on the Cassini mission page maintained by JPL.

Posted on by Paul Scott Anderson

Enceladus and its Water Geysers Pose Again for Cassini

View of Enceladus' surface, image taken October 19, 2011. NASA/JPL-Caltech/Space Science Institute

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Saturn’s tiny moon Enceladus was the centre of attention for the Cassini spacecraft again last week, with beautiful new photos being released of the moon and its water vapour geysers erupting from the south pole. Some views show surface detail on the moon, some are of the geysers themselves and there is a very nice shot of Enceladus silhouetted against Saturn and its rings in the background. There is even a dual ultraviolet stellar occultation in which two of the stars in the belt of the constellation Orion are seen shining through the plumes! Even though these are still raw, unprocessed images, they again capture the beauty of Enceladus and the Saturnian system.

These new images were taken October 19, 2011 during the E-15 flyby, in which Cassini flew about 1,230 kilometres (765 miles) above the surface of Enceladus. The geysers can be seen in the image below, albeit these are not the closest views that Cassini has obtained. Still, it can be clearly seen how far they extend out from the moon, for a few hundred kilometres.

Enceladus and its water vapour geysers, image taken October 19, 2011. Credit: NASA/JPL-Caltech/Space Science Institute

Some surface detail can be seen in the next image below, a hint of the geological complexity of this moon, most notably seen in the “tiger stripe” fissures at the south pole, where the geysers erupt from inside the moon, escaping to the vacuum of space outside, where the water vapour freezes and falls back to the surface of Enceladus as a form of snow. As some have suggested, Enceladus may be a good place for skiing (with the snow being a very fine powder, although the extremely low gravity would probably interfere too much…)!

Enceladus silhouetted against the clouds and rings of Saturn in the background (the rings are edge-on in this view), image taken October 19, 2011. Credit: NASA/JPL-Caltech/Space Science Institute

Having a personal fascination with Enceladus, I was reminded of an older “Captain’s Log” entry on the CICLOPS web site (2006), by Cassini imaging team leader Carolyn Porco, after the initial discovery of the geysers. In part:

“Our detailed analyses of these images have led us to a remarkable conclusion, documented in a paper to be published in the journal SCIENCE tomorrow, that the jets are erupting from pockets of liquid water, possibly as close to the surface as ten meters… a surprising circumstance for a body so small and cold. Other Cassini instruments have found that the fractures on the surface and the plume itself contain simple organic materials, and that there is more heat on average emerging from the south polar terrain, per square meter, than from the Earth.

Gathering all the evidence and steeling ourselves for the “shockwave spread ’round the world”, we find ourselves staring at the distinct possibility that we may have on Enceladus subterranean environments capable of supporting life. We may have just stumbled upon the Holy Grail of modern day planetary exploration. It doesn’t get any more exciting than this.

A great deal more analysis and further exploration with Cassini must ensue before this implication becomes anything more than a suggestion. But at the moment, the prospects are staggering. Enceladus may have just taken center stage as the body in our solar system, outside the Earth, having the most easily accessible bodies of organic-rich water and, hence, significant biological potential.

Many years from now, it may well be that we and those who follow us will look back on these explorations of Saturn and take our discoveries on this otherwise cold little world to be the most wondrous of any we’ve ever made.

Future explorers of Saturn will have much to look forward to.”

Posted on by Paul Scott Anderson

A Tale of Three Moons: Is There Life in the Outer Solar System?

The cracked ice surface of Europa. Credit: NASA/JPL

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Until fairly recently, the search for life elsewhere in the solar system has focused primarily on Mars, as it is the most Earth-like of all the other planets in the solar system. The possibility of finding any kind of life farther out in the outer solar system was considered very unlikely at best; too cold, too little sunlight, no solid surfaces on the gas giants and no atmospheres to speak of on any of the moons apart from Titan.

But now, some of the places that were previously considered the least likely to hold life have turned out to be perhaps some of the most likely to provide habitable environments. Moons that were thought be cold and frozen for eons are now known to be geologically active, in surprising ways. One of them is the most volcanically active place known in the solar system. At least two others appear to have oceans of liquid water beneath their surfaces. That’s right, oceans. And geysers. On the surface, they are ice worlds, but below, they are water worlds. Then there’s the one with rain, rivers, lakes and seas, but made of liquid methane instead of water. Billions of kilometres farther out from the Sun than the Earth. Who would have thought? Let’s look at those last three in a bit more detail…

Ever since the film 2001: A Space Odyssey first came out, Europa has been the subject of fascination. A small, icy moon orbiting Jupiter, its depiction in that movie, as an inhabited world beneath its ice crust was like a sort of foreshadowing, before the Voyager and Galileo spacecraft gave us our first real close-up looks of this intriguing place. Its surface shell of ice is covered with long cracks and fissures, giving it an appearance much like ice floes at the poles on Earth. More surprising though, was the discovery that, also like on Earth, this ice cover most likely is floating on top of a deep layer of liquid water below. In Europa’s case though, the water layer appears to cover the entire moon, a global subsurface ocean. How is this possible? If there is liquid water, there must be heat (or high concentrations of salts or ammonia), and if you have water and heat, could there be something living in those waters? Gravitational tugging from Jupiter indeed appears to provide enough heat to keep the water liquid instead of frozen. The environment is now thought to be similar to ocean bottoms on Earth. No sunlight, but if there are volcanic vents generating heat and minerals, as on Earth, such a spot could be ideal for at least simple forms of life. On Earth, places like these deep in the oceans are brimming with organisms which don’t require sunlight to survive.

Water vapour geysers on Enceladus. Credit: NASA/JPL

Then there’s Enceladus. Another very small icy moon, orbiting Saturn. Geological activity was considered very unlikely on such a tiny world, only a few hundred kilometres in diameter. But then Cassini saw the geysers, plumes of material erupting from the south polar region through large, warmer cracks nicknamed “tiger stripes.” Cassini has now flown directly through the geysers, analyzing their composition, which is mostly water vapour, ice particles, salts and organics. The latest analysis based on the Cassini data indicates that they almost certainly originate from a sea or ocean of liquid water below the surface. Warm, salty water loaded with organics; could Enceladus be another possible niche for extraterrestrial life? As with Europa, only further missions will be able to answer these questions, but the possibilities are exciting.

Radar image of one of many methane lakes on Titan. Credit: NASA/JPL

Titan is even more fascinating in some ways, the largest moon of Saturn. It is perpetually shrouded in a thick smoggy atmosphere of nitrogen and methane, so the surface has never been visible until now, when Cassini, and its small lander probe Huygens, first looked below the smog and clouds. Titan is like an eerily alien version of Earth, with rain, rivers, lakes and seas, but being far too cold for liquid water (not much heat here), its “water cycle” is composed of liquid methane/ethane. Appearance-wise, the surface and geology look amazingly Earth-like, but the conditions are uniquely Titan. For that reason, it has long been considered that the chances of any kind of life existing here are remote at best. In the last few years however, some scientists are starting to consider the possibility of life forming in just such environments, using liquids other than water, even in such cold conditions. Could life occur in a liquid methane lake or sea? How would it differ from water-based life? Last year, a discovery was made which might be interpreted as evidence of methane-based life on Titan – a seeming disappearance of hydrogen from the atmosphere near the surface and a lack of acetylene on the surface. Previous theoretical studies had suggested that those two things, if ever found, could be evidence for methane-based lifeforms consuming the hydrogen and acetylene. All of this is still highly speculative, and while a chemical explanation is probably more likely according to the scientists involved, a biological one cannot be ruled out yet. Future proposed missions for Titan include a floating probe to land in one of the lakes and a balloon to soar over the landscape, pursuing such mysteries as never before. How cool is that?

Oh, and the moon that is the most volcanically active place in the solar system? Io, although with the only known forms of liquid there being extremely hot lavas on that sulfuric hothouse, the chances of life are still thought to be unbelievably slim. But that’s ok when you start to find out that worlds with oceans and lakes, etc. may be much more common than previously imagined…

Posted on by Nancy Atkinson

Suitable For Framing: Latest Eye Candy from Cassini

Enceladus and Tethys hang below Saturn's rings in this image from the Cassini spacecraft. Credit: NASA/JPL-Caltech/SS

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Another Cassini stunner! This gorgeous, suitable-for-framing image shows two of Saturn’s moons hanging below the planet’s rings, as if strung on a necklace. Beautiful! Enceladus (504 kilometers, 313 miles across) appears just below the rings, while Tethys (1062 kilometers, 660 miles across) appears below. In this shot, Cassini is also closer to Tethys than Enceladus: the spacecraft is 208,000 kilometers (139,000 miles) from Tethys and 272,000 kilometers (169,000 miles) from Enceladus. This image was taken on September 13, 2011.

See below for some raw images from Cassini’s October 1 close fly by of Enceladus, including a great shot of the moon hovering in front of Saturn’s rings, and a view of the geysers.


A closeup view of Enceladus with Saturn's rings in the background. This raw image was taken on Oct. 1, 2011. Credit: NASA/JPL/Space Science Institute

A view of Enceladus from farther away, with the rings slicing through the view of Saturn in the background. Credit: NASA/JPL/Space Science Institute
A view of the geysers on Enceladus, from Cassini's latest close flyby of the moon, on October 1, 2011.Credit: NASA/JPL/Space Science Institute
Posted on by Tammy Plotner

Water, Water Everywhere… And A Few Drops For Saturn, Too!

Recent Cassini images of Saturn's moon Enceladus backlit by the sun show the fountain-like sources of the fine spray of material that towers over the south polar region. This image was taken looking more or less broadside at the "tiger stripe" fractures observed in earlier Enceladus images. It shows discrete plumes of a variety of apparent sizes above the limb (edge) of the moon. This image was acquired on Nov. 27, 2005. Image Credit: NASA/JPL/Space Science Institute

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In 2005, NASA’s Cassini spacecraft gave us an incredible view of Enceladus chuffing out fountains of water vapor and ice. This action creates an enormous halo of gas, dust and ice that surrounds this Saturnian satellite and enables the planet’s E ring. Now Enceladus is once again in the spotlight as the only moon in the Solar System known to significantly contribute to its parent planet’s chemistry.

Earlier this year, ESA announced that its Herschel Space Observatory had observed a huge torus of water vapor around Saturn which apparently originated from Enceladus. It spans approximately 600,000 kilometers across and runs about 60,000 kilometers deep, but more so than its size is what it appears to be doing… adding water to Saturn’s upper atmosphere. Because the vapor isn’t detectable at visible wavelengths, this observation came as revelation for the Herschel scope.

“Herschel is providing dramatic new information about everything from planets in our own solar system to galaxies billions of light-years away,” said Paul Goldsmith, the NASA Herschel project scientist at NASA’s Jet Propulsion Laboratory, Pasadena, California.

While the Herschel infrared observation is new, the indication of a vapor torus around Saturn isn’t. NASA’s Voyager and Hubble missions had given astronomers clues in the past. In 1997, the European Space Agency’s Infrared Space Observatory cited water in Saturn’s atmosphere and two years later NASA’s Submillimeter Wave Astronomy Satellite confirmed it again. But this confirmation only added up to a puzzle. Water found in Saturn’s lower cloud levels couldn’t rise past the colder, upper deck… So where was the water coming from? The answer came in the form of Herschel’s observations and some very astute computer modeling.

“What’s amazing is that the model, which is one iteration in a long line of cloud models, was built without knowledge of the observation.” says Tim Cassidy, a recent post-doctoral researcher at JPL who is now at the University of Colorado’s Laboratory for Atmospheric and Space Physics, Boulder. “Those of us in this small modeling community were using data from Cassini, Voyager and the Hubble telescope, along with established physics. We weren’t expecting such detailed ‘images’ of the torus, and the match between model and data was a wonderful surprise.”

Through these simulations, researchers hypothesized that much of the water in the torus was simply lost to space and some is pulled back by gravity to add material to Saturn’s rings. However, it’s the 3-5% that made it back to Saturn’s atmosphere that’s the most interesting. Just how much water vapor is out there? Thanks to combining information from both Herschel and the Ultraviolet Imaging Spectrograph (UVIS) instrument aboard the Cassini spacecraft, we’ve learned that about 12,000 kilograms is being ejected from Enceladus every minute. Can you image how much that would add up to in the period of a year… or more?!

“With the Herschel measurements of the torus from 2009 and 2010 and our cloud model, we were able to calculate a source rate for water vapor coming from Enceladus,” said Cassidy. “It agrees very closely with the UVIS finding, which used a completely different method.”

“We can see the water leaving Enceladus and we can detect the end product — atomic oxygen — in the Saturn system,” said Cassini UVIS science team member Candy Hansen, of the Planetary Science Institute, Tucson, Ariz. “It’s very nice with Herschel to track where it goes in the meantime.”

A tiny percentage adds up to some mighty big numbers, and the water molecules from the torus impact Saturn’s atmosphere to a great degree by contributing hydrogen and oxygen.

“When water hangs out in the torus, it is subject to the processes that dissociate water molecules,” said Hansen, “first to hydrogen and hydroxide, and then the hydroxide dissociates into hydrogen and atomic oxygen.” This oxygen is dispersed through the Saturn system. “Cassini discovered atomic oxygen on its approach to Saturn, before it went into orbit insertion. At the time, no one knew where it was coming from. Now we do.”

Very few days go by that we don’t learn something new about the Solar System and its inner workings. Thanks to observations like those done by the Herschel Space Observatory and missions like Cassini-Huygens, we’re able to further understand the dynamics behind the beauty… and how a tiny player can carry a major role.

“The profound effect this little moon Enceladus has on Saturn and its environment is astonishing,” said Hansen.

Original Story Source: JPL News Release.

Posted on by Ken Kremer

Cassini’s Majestic Saturn Moon Quintet

A quintet of Saturn's moons come together in the Cassini spacecraft's field of view for this portrait. From left to right: Janus, Pandora, Enceladus, Mimas and Rhea. Credit: NASA/JPL-Caltech/Space Science Institute

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Check out this gorgeous new portrait of a Saturnian moon quintet taken by Earths’ emissary – NASA’s Cassini Orbiter. The moons are majestically poised along a backdrop of Saturn’s rings, fit for an artist’s canvas.

Janus, Pandora, Enceladus, Mimas and Rhea are nearly lined up (from left to right) in this view acquired by Cassini at a distance of approximately 684,000 miles (1.1 million kilometers) from Rhea and 1.1 million miles (1.8 million kilometers) from Enceladus.

The newly released image was taken by Cassini’s narrow angle camera on July 29, 2011. Image scale is about 4 miles (7 kilometers) per pixel on Rhea and 7 miles (11 kilometers) per pixel on Enceladus.

Cassini will stage a close flyby of Enceledus – Satarn’s geyser spewing moon – in about two weeks, swooping within 99 km

Moon Facts from JPL:
Janus (179 kilometers, or 111 miles across) is on the far left. Pandora (81 kilometers, or 50 miles across) orbits between the A ring and the thin F ring near the middle of the image. Brightly reflective Enceladus (504 kilometers, or 313 miles across) appears above the center of the image. Saturn’s second largest moon, Rhea (1,528 kilometers, or 949 miles across), is bisected by the right edge of the image. The smaller moon Mimas (396 kilometers, or 246 miles across) can be seen beyond Rhea also on the right side of the image.

This view looks toward the northern, sunlit side of the rings from just above the ring plane. Rhea is closest to Cassini here. The rings are beyond Rhea and Mimas. Enceladus is beyond the rings.

The simple graphic below shows dozens of Saturn’s moons – not to scale. So far 62 have been discovered and 53 have been officially named.

Saturn’s moons. Click on link below to learn more about each moon. Credit: NASA/JPL

Learn more about Saturn’s moons at this link

List of Saturn’s officially named moons:
Aegaeon, Aegir, Albiorix, Anthe, Atlas, Bebhionn, Bergelmir, Bestla, Calypso, Daphnis, Dione, Enceladus, Epimetheus, Erriapus, Farbauti, Fenrir, Fornjot, Greip, Hati, Helene, Hyperion, Hyrrokkin, Iapetus, Ijiraq, Janus, Jarnsaxa, Kari, Kiviuq, Loge, Methone, Mimas, Mundilfari, Narvi, Paaliaq, Pallene, Pan, Pandora, Phoebe, Polydeuces, Prometheus, Rhea, Siarnaq, Skadi, Skoll, Surtur, Suttung, Tarqeq, Tarvos, Telesto, Tethys, Thrym, Titan and Ymir.

Posted on by Nancy Atkinson

Enceladus Rains Water on Saturn

At least four distinct plumes of water ice spew out from the south polar region of Saturn's moon Enceladus. Credit: NASA/JPL/Space Science Institute

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It’s raining on Saturn! Well, kind of. Actually, not really. But there’s some really cool news about Saturn, Enceladus and water – great topics, all. The bubbly water shooting from the moon Enceladus is responsible for the “mystery” water that was found in Saturn’s upper atmosphere several years ago. Observations with the Herschel space observatory has shown that water ice from geysers on Enceladus forms a giant ring of water vapor around Saturn.

Astronomers from the ESA’s Infrared Observatory discovered the presence of trace amounts of water in Saturn’s atmosphere back in 1997, but couldn’t really find an explanation for why it was there and how it got there. Water vapor can’t be seen in visible light, but Herschel’s infrared vision was able to track down the source of the water vapor.

Enceladus expels around 250 kg of water vapor every second, through a collection of jets from the south polar region known as the Tiger Stripes because of their distinctive surface markings. Much of the ice ends up in orbit around Saturn, creating the hazy E ring in which Enceladus resides.

But a small amount reaches Saturn – about 3% to 5% of Enceladus’s ejected water ends up on the home planet of Saturn.

Phil Plait, The Bad Astronomer figured out that a decent rain shower on Earth is 7,000,000,000,000 times heavier than the rainfall on Saturn. So, not a lot of water makes it to Saturn.

But the fact that a moon is having an effect on its planet is unprecedented, as far as we know.

“There is no analogy to this behaviour on Earth,” said Paul Hartogh, Max-Planck-Institut für Sonnensystemforschung, in Germany, who led the collaboration on the analysis of these results. “No significant quantities of water enter our atmosphere from space. This is unique to Saturn.”

The running theory is that Enceladus has a liquid subsurface ocean of Perrier-like bubbly (and maybe salty) water. No one knows yet how much water lies beneath the moon’s surface, but it is thought that the pressure from the rock and ice layers above combined with heat from within force the water up through the Tiger Stripes. When this water reaches the surface it instantly freezes, sending plumes of ice particles hundreds of miles into space.

The total width of the torus is more than 10 times the radius of Saturn, yet it is only about one Saturn radius thick. Enceladus orbits the planet at a distance of about four Saturn radii, replenishing the torus with its jets of water.

The water in Saturn’s upper atmosphere is ultimately transported to lower levels, where it condenses. But scientists say the amounts are so tiny that the resulting clouds are not observable.

Again, despite its enormous size, this torus has it has escaped detection until now because of how water vapor is transparent to visible light but not at the infrared wavelengths Herschel was designed to see.

“Herschel has proved its worth again. These are observations that only Herschel can make,” says Göran Pilbratt, ESA Herschel Project Scientist. “ESA’s Infrared Space Observatory found the water vapour in Saturn’s atmosphere. Then NASA/ESA’s Cassini/Huygens mission found the jets of Enceladus. Now Herschel has shown how to fit all these observations together.”

Read the team’s paper here.

Source: ESA

Posted on by Jason Major

Enceladus’ Salty Surprise

Enceladus' signature ice geysers in action. NASA / JPL / SSI

 

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Researchers on the Cassini mission team have identified large salt grains in the plumes emanating from Saturn’s icy satellite Enceladus, making an even stronger case for the existence of a salty liquid ocean beneath the moon’s frozen surface.

Cassini first discovered the jets of water ice particles in 2005; since then scientists have been trying to learn more about how they behave, what they are made of and – most importantly – where they are coming from. The running theory is that Enceladus has a liquid subsurface ocean of as-of-yet undetermined depth and volume, and pressure from the rock and ice layers above combined with heat from within force the water up through surface cracks near the moon’s south pole. When this water reaches the surface it instantly freezes, sending plumes of ice particles hundreds of miles into space.

Enceladus inside the E ring

Much of the ice ends up in orbit around Saturn, creating the hazy E ring in which Enceladus resides.

Although the discovery of the plumes initially came as a surprise, it’s the growing possibility of liquid water that’s really intriguing – especially that far out in the Solar System and on a little 504-km-wide moon barely the width of Arizona. What’s keeping Enceladus’ water from freezing as hard as rock? It could be tidal forces from Saturn, it could be internal heat from its core, a combination of both – or something else entirely… astronomers are still hard at work on this mystery.

Now, using data obtained from flybys in 2008 and 2009 during which Cassini flew directly through the plumes, researchers have found that the particles in the jets closest to the moon contain large sodium- and potassium-rich salt grains. This is the best evidence yet of the existence of liquid salt water inside Enceladus – a salty underground ocean.

“There currently is no plausible way to produce a steady outflow of salt-rich grains from solid ice across all the tiger stripes other than salt water under Enceladus’s icy surface.”

– Frank Postberg, Cassini team scientist, University of Heidelberg, Germany

Looking down into a jetting "tiger stripe"

If there indeed is a reservoir of liquid water, it must be pretty extensive since the numerous plumes are constantly spraying water vapor at a rate of 200 kg (400 pounds) every second – and at several times the speed of sound! The plumes are ejected from points within long, deep fissures that slash across Enceladus’ south pole, dubbed “tiger stripes”.

Recently the tiger stripe region has also been found to be emanating a surprising amount of heat, even further supporting a liquid water interior – as well as an internal source of energy. And where there’s liquid water, heat energy and organic chemicals – all of which seem to exist on Enceladus – there’s also a case for the existence of life.

“This finding is a crucial new piece of evidence showing that environmental conditions favorable to the emergence of life can be sustained on icy bodies orbiting gas giant planets.”

– Nicolas Altobelli, ESA project scientist for Cassini

Enceladus has intrigued scientists for many years, and every time Cassini takes a closer look some new bit of information is revealed… we can only imagine what other secrets this little world may hold. Thankfully Cassini is going strong and more than happy to keep on investigating!

“Without an orbiter like Cassini to fly close to Saturn and its moons — to taste salt and feel the bombardment of ice grains — scientists would never have known how interesting these outer solar system worlds are.”

– Linda Spilker, Cassini project scientist at JPL

The findings were published in this week’s issue of the journal Nature.

Read more in the NASA press release here.

Image credits: NASA / JPL / Space Science Institute

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Jason Major is a graphic designer, photo enthusiast and space blogger. Visit his website Lights in the Dark and follow him on Twitter @JPMajor or on Facebook for the most up-to-date astronomy awesomeness!

Posted on by Nancy Atkinson

Insanely Awesome Raw Cassini Images of Titan and Enceladus

Raw Cassini image of Titan and Enceladus backdropped by Saturn's rings. Image Credit: NASA/JPL/Space Science Institute

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An incredible set of images are beaming back from the Cassini spacecraft as it orbits Saturn, snapping away at the sights. The moons Titan and Enceladus snuggling up together in front of Saturn’s rings creates an amazing view, especially when they are all lined up together. These were taken on May 21, 2011. I’ve posted some of what I think are the most amazing, below, or you can see the whole set at the Cassini raw images page. When the Cassini imaging team gets a chance to process (and colorize) these, they’ll likely go down as some of the most representative images from the entire mission.


Titan snuggles up to Saturn and its rings. Image credit: NASA/JPL/Space Science Institute

Titan, Enceladus and an onside view of Saturn's rings. Credit: NASA/JPL/Space Science Institute

Hat tip to Stu Atkinson!