Titan’s Seas

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The Sun Shines on Titan’s Seas : Image NASA/JPL-CalTech/Univ. Arizona/Univ. Idaho

The movie Interstellar took the crew of the Endurance to an ocean world with giant, wormhole driven waves, and then a frozen wasteland of a planet which left many audience members looking for a marauding Wampa snow beast. The point of departure for all that fun, a stable wormhole around Saturn.

It should have been around Titan, a world offering both waves, albeit much, much smaller, and on hydrocarbon seas, and frozen vistas, including atmopheric ice crystals similar to what the Ranger encountered on its descent.

In the latest dispatch from the Cassini spacecraft, which has seemed to discover everything except a wormhole in the Saturn system, NASA describes mostly successful efforts to map the depth of bays in two of Titan’s seas. The full story is here.

Credit: NASA/JPL-CalTech

Credit: NASA/JPL-CalTech

From the NASA News story:

“The August Titan flyby also included a segment designed to collect altimetry (or height) data, using the spacecraft’s radar instrument along a 120-mile (200-kilometer) shore-to-shore track of Kraken Mare. For a 25-mile (40-kilometer) segment of this data along the sea’s eastern shoreline, Cassini’s radar beam bounced off the sea bottom and back to the spacecraft, revealing the sea’s depth in that area. This region, which is near the mouth of a large, flooded river valley, showed depths of 66 to 115 feet (20 to 35 meters). Cassini will perform this experiment one last time in January 2015, to try to measure the depth of Punga Mare. Punga Mare is the smallest of three large seas in Titan’s far north, and the only sea whose depth has not been observed by Cassini.

Scientists think that, for the areas in which Cassini did not observe a radar echo from the seafloor, Kraken Mare might be too deep for the radar beam to penetrate.  Alternatively, the signal over this region might simply have been absorbed by the liquid, which is mostly methane and ethane. The altimetry data for the area in and around Kraken Mare also showed relatively steep slopes leading down to the sea, which also suggests the Kraken Mare might indeed be quite deep.”

Simply amazing, and perhaps another opportunity to decry NASA’s plan to crash the Cassini probe into Saturn rather than keep flying it until another probe is on the way, and then leave Cassini in a safe orbit as the first permanent exhibit in the Smithsonian Air and Space Museum of the Outer Planets. It sure beats a farmhouse.

 

Cassini Journals: A Shocking Encounter at Hyperion and an Ocean on Mimas

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A Shocking Encounter at Hyperion:  NASA/JPL-Caltech/Space Science Institute

This week brought two new findings from the Cassini spacecraft in the Saturn system.

The first involved data from a September 26, 2005 flyby of Saturn’s bizarrely shaped moon Hyperion. According to new analysis, during the approach, Cassini was struck by a beam of electrons coming from the moon’s surface, which momentarily the connected the spacecraft to the moon, transmitting what amounted to a 200 volt electric shock.  Regrettably, (or perhaps not), the reason for the encounter encounter was not as exciting as it could have been. There was no ancient relic of an alien civilization sending out distress signals, nor was it a prelude to invasion. Instead it was the first confirmed instance of a charged surface on a world other than our own Moon. The key word is “confirmed,” as scientists believe many other celestial objects will be discovered to be similarly charged.

The complete story is here.

Also coming from the Cassini mission, a possibly very surprising finding regarding another of the Saturn’s moons, Mimas. In a study reported in the Oct 17 issue of Science, researchers have determined that a slight wobble in the moon’s orbit indicates something unusual is happening.

From the JPL news story:

“The data suggest that something is not right, so to speak, inside Mimas,” said Radwan Tajeddine, a Cassini research associate at Cornell University, Ithaca, New York, and lead author on the paper. “The amount of wobble we measured is double what was predicted.”

While the wobble could be caused by the presence of a football shaped, frozen core, another and altogether more intriguing possibility is that Mimas is hiding a subsurface ocean. If so, it adds to a growing awareness that our solar system is a much wetter place than we one thought it to be.  From discoveries of water molecules on the Moon and significant ice deposits on Mars, to the hydrocarbon seas of Titan, as well as subsurface oceans on Enceladus and Europa, we are quickly finding ours is not the only “water world.”

Mimas Mosaic  Image credit: NASA/JPL-Caltech/Space Science Institute

Mimas Mosaic
Image credit: NASA/JPL-Caltech/Space Science Institute

 

 

Europa Clipper: Cubesats But No Nuclear Power

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Artists Concept: Image CredIt JPL

One recurring theme in coverage from Innerspace.net is a lamentation over the lack of any flagship class outer planet mission to follow in the wake of the spectacularly successful Cassini/Huygens mission to Saturn. While Innerspace is predominately focused on human exploration and settlement, and in particular the contributions being made by NewSpace companies, sometimes nothing fires the imagination like the surprise coming from new and unexpected discoveries. In this regard, Cassini has been magnificent. And while some would like to see a follow on mission as soon as possible, Jupiter’s enigmatic moon Europa is currently the focus of much of the space science community.

NASA is now in the pre-planning stages of a mission to Jupiter’s most famous moon, Europa Clipper, and although it has yet to receive a full go ahead, appears increasingly likely to come together. Last week’s International Astronautical Congress in Toronto brought several items regarding the mission into the news.

First in a story reported in Space News, word came that the mission will be solar powered.

“In an Oct. 3 presentation at the 65th International Astronautical Congress here, Europa Clipper deputy project manager Thomas Magner of the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, said that using large solar panels for the mission was both technically viable and less expensive than a radioisotope thermoelectric generator (RTG).

“For the last two years, we did extensive risk reduction work looking at whether solar is feasible,” Magner said. “We found that solar works fine, so our final decision about two months ago was to go to solar.”

As the story points out, the decision does not set a precedent, as the Juno mission, currently en route to Jupiter for a planned 2016 arrival is solar powered as well. While solar will may very well meet the mission objectives, it is also true a major contributing factor is the reality that the United States has seriously dropped the ball in securing adequate production of the PU-238 plutonium pellets which power the nuclear RTG’s needed for more demanding deep space missions. For a nation which professes to (and does) lead the world in deep space exploration, the PU-238 issue continues to be a terribly disappointing failure which will take years to correct, if indeed it ever is.

On another possibly ominous note, while the Europa Clipper would not lift off until 2022 at the earliest, and having yet to be approved does not require a launch vehicle,  planners are keeping open the possibility of using the Space Launch System.

From the same piece:

“An alternative approach would use NASA’s still-in-development Space Launch System heavy-lift rocket to send Europa Clipper on a direct trajectory to Jupiter. A mid-2022 launch would allow the spacecraft to reach Jupiter in fewer than three years, without the need of any flybys.

Launching on SLS, Magner said, would reduce the costs of operating Europa Clipper given the much shorter travel time to Jupiter, and also simplify the thermal design since the spacecraft would not have to perform a Venus flyby in order to reach Jupiter. However, it was unclear how much more Europa Clipper would have to pay for an SLS launch.”

While there is definite merit in looking for faster means to reach the outer planets than afforded through time consuming planetary flybys, which can add years to a mission, a fuller examination of other options might be in order.  It has been clear for some time that desperately searching to find uses for SLS, just as it was with Shuttle prior to 1986, NASA might very well be putting the same set of blinders on.

Somewhat ironically, the other news item related to Europe Clipper comes from the Jet Propulsion Laboratory and regards the use of cubesats for enhancing the mission.

From the JPL News Story:

“NASA’s Jet Propulsion Laboratory in Pasadena, California, has chosen proposals from 10 universities to study CubeSat concepts that could enhance a Europa mission concept currently under study by NASA. The CubeSat concepts will be incorporated into a JPL study describing how small probes could be carried as auxiliary payloads. The CubeSats would then be released in the Jovian system to make measurements and enhance our understanding of Jupiter’s moon Europa.

CubeSats are small, lightweight and low-cost satellites, often only inches on a side. With support from NASA, JPL is working to include small spacecraft on deep space exploration missions to complement primary spacecraft.

The conceptual Europa mission, called Europa Clipper, would conduct detailed reconnaissance of the icy moon and investigate whether it could harbor conditions suitable for life.

Awardees will receive up to $25,000 each to develop their CubeSat concepts for inclusion in the study, which will be completed next summer.

CubeSat concepts from the following universities were chosen by JPL’s Planetary CubeSat office for inclusion in the study:

— Arizona State University, Tempe

— Georgia Tech Research Corporation, Atlanta

— Stanford University, Stanford, California

— The Regents of New Mexico State University, Las Cruces, New Mexico

— The Regents of the University of Colorado, Boulder

— The Regents of the University of Michigan, Ann Arbor

— University of Alaska, Fairbanks

— University of Southern California, Los Angeles

— University of Illinois, Urbana

— University of Washington, Seattle

The universities’ Europa science objectives for their CubeSats would include reconnaissance for future landing sites, gravity fields, magnetic fields, atmospheric and plume science, and radiation measurements.

“We’ve seen some innovative and quite creative surprises among the CubeSat ideas submitted by these universities,” said Barry Goldstein, pre-project manager for the Europa Clipper mission concept. “Using CubeSats for planetary exploration is just now becoming possible, so we want to explore how a future mission to Europa might take advantage of them.”

 

Cassini Finds Strange Feature in Titan’s Sea

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Three images show an unusual feature in Titan’s sea. Image Credit: NASA/JPL-Caltech/ASI/Cornell

Note: Yet another in a long series of intriguing findings from the Cassini spacecraft operating in the Saturn system, and another reason to bemoan the lack of any planned follow up to this groundbreaking spacecraft.

From JPL News:

“NASA’s Cassini spacecraft is monitoring the evolution of a mysterious feature in a large hydrocarbon sea on Saturn’s moon Titan. The feature covers an area of about 100 square miles (260 square kilometers) in Ligeia Mare, one of the largest seas on Titan. It has now been observed twice by Cassini’s radar experiment, but its appearance changed between the two apparitions.

Images of the feature taken during the Cassini flybys are available at:

http://photojournal.jpl.nasa.gov/catalog/PIA18430

The mysterious feature, which appears bright in radar images against the dark background of the liquid sea, was first spotted during Cassini’s July 2013 Titan flyby. Previous observations showed no sign of bright features in that part of Ligeia Mare. Scientists were perplexed to find the feature had vanished when they looked again, over several months, with low-resolution radar and Cassini’s infrared imager. This led some team members to suggest it might have been a transient feature. But during Cassini’s flyby on August 21, 2014, the feature was again visible, and its appearance had changed during the 11 months since it was last seen.

Scientists on the radar team are confident that the feature is not an artifact, or flaw, in their data, which would have been one of the simplest explanations. They also do not see evidence that its appearance results from evaporation in the sea, as the overall shoreline of Ligeia Mare has not changed noticeably.

The team has suggested the feature could be surface waves, rising bubbles, floating solids, solids suspended just below the surface, or perhaps something more exotic.

The researchers suspect that the appearance of this feature could be related to changing seasons on Titan, as summer draws near in the moon’s northern hemisphere. Monitoring such changes is a major goal for Cassini’s current extended mission.

“Science loves a mystery, and with this enigmatic feature, we have a thrilling example of ongoing change on Titan,” said Stephen Wall, the deputy team lead of Cassini’s radar team, based at NASA’s Jet Propulsion Laboratory in Pasadena, California. “We’re hopeful that we’ll be able to continue watching the changes unfold and gain insights about what’s going on in that alien sea.”

Cassini Captures Shining Mimas Against the Shadow of Saturn’s Rings

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Although Innerspace.net tends to focus on Mars as the most inhabitable planet outside Earth, Saturn’s system holds a unique fascination, much of it due to the amazing Cassini space probe. It is also the case because even though it is much further out than Jupiter and its many moons, Saturn’s system does not present the extreme radiation environment found in the vicinity of the largest planet.

For the crewed spacecraft which someday approaches the Saturnian system, (as well as the spacecraft there today) it is in some way analogous to what it might be like to enter a new solar solar system entirely. From hydrocarbon lakes on Titan to ice geysers on Enceladus, as well as smaller moons such as Mimas and of course the rings themselves, with their own tiny moonlets, we can only envy first explorers to witness it up close.  For the time being however, Cassini is providing a steady stream of new data and images.

 

NASA/JPL News Story

Dot Against the Dark

As if trying to get our attention, Mimas is positioned against the shadow of Saturn’s rings, bright on dark. As we near summer in Saturn’s northern hemisphere, the rings cast ever larger shadows on the planet.

With a reflectivity of about 96 percent, Mimas (246 miles, or 396 kilometers across) appears bright against the less-reflective Saturn.

This view looks toward the sunlit side of the rings from about 10 degrees above the ringplane. The image was taken with the Cassini spacecraft wide-angle camera on July 13, 2014 using a spectral filter which preferentially admits wavelengths of near-infrared light centered at 752 nanometers.

The view was acquired at a distance of approximately 1.1 million miles (1.8 million kilometers) from Saturn and approximately 1 million miles (1.6 million kilometers) from Mimas. Image scale is 67 miles (108 kilometers) per pixel at Saturn and 60 miles (97 kilometers) per pixel at Mimas.

The Cassini-Huygens mission 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 mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

New Horizons Crosses Neptune’s Orbit on Way to Pluto

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Image Credit: NASA/JPL

Last week, NASA released this enhanced video of images Voyager 2 shot of Neptune’s moon Triton as it sailed past in 1989. Today, the New Horizons spacecraft crossed Neptune’s orbit on the way to its own flyby of now minor planet Pluto. The full NASA story is below.

NASA New Story

August 25, 2014

NASA’s Pluto-bound New Horizons spacecraft has traversed the orbit of Neptune. This is its last major crossing en route to becoming the first probe to make a close encounter with distant Pluto on July 14, 2015.

The sophisticated piano-sized spacecraft, which launched in January 2006, reached Neptune’s orbit — nearly 2.75 billion miles (4.4. billion kilometers) from Earth — in a record eight years and eight months. New Horizons’ milestone matches precisely the 25th anniversary of the historic encounter of NASA’s Voyager 2 spacecraft with Neptune on Aug. 25, 1989.

“It’s a cosmic coincidence that connects one of NASA’s iconic past outer solar system explorers, with our next outer solar system explorer,” said Jim Green, director of NASA’s Planetary Science Division, NASA Headquarters in Washington. “Exactly 25 years ago at Neptune, Voyager 2 delivered our ‘first’ look at an unexplored planet. Now it will be New Horizons’ turn to reveal the unexplored Pluto and its moons in stunning detail next summer on its way into the vast outer reaches of the solar system.”

New Horizons now is about 2.48 billion miles (nearly 4 billion kilometers) from Neptune — nearly 27 times the distance between Earth and our sun — as it crosses the giant planet’s orbit at 7:04 p.m. PDT (10:04 p.m. EDT) Monday. Although the spacecraft will be much farther from the planet than Voyager 2’s closest approach, New Horizons’ telescopic camera was able to obtain several long-distance “approach” shots of Neptune on July 10.

“NASA’s Voyager 1 and 2 explored the entire middle zone of the solar system where the giant planets orbit,” said Alan Stern, New Horizons principal investigator at the Southwest Research Institute in Boulder, Colorado. “Now we stand on Voyager’s broad shoulders to explore the even more distant and mysterious Pluto system.”

Several senior members of the New Horizons science team were young members of Voyager’s science team in 1989. Many remember how Voyager 2’s approach images of Neptune and its planet-sized moon Triton fueled anticipation of the discoveries to come. They share a similar, growing excitement as New Horizons begins its approach to Pluto.

“The feeling 25 years ago was that this was really cool, because we’re going to see Neptune and Triton up-close for the first time,” said Ralph McNutt of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland, who leads the New Horizons energetic-particle investigation and served on the Voyager plasma-analysis team. “The same is happening for New Horizons. Even this summer, when we’re still a year out and our cameras can only spot Pluto and its largest moon as dots, we know we’re in for something incredible ahead.”

Voyager’s visit to the Neptune system revealed previously unseen features of Neptune itself, such as the Great Dark Spot, a massive storm similar to, but not as long-lived, as Jupiter’s Great Red Spot. Voyager also, for the first time, captured clear images of the ice giant’s ring system, too faint to be clearly viewed from Earth. “There were surprises at Neptune and there were surprises at Triton,” said Ed Stone, Voyager’s long-standing project scientist from the California Institute of Technology in Pasadena. “I’m sure that will continue at Pluto.”

Many researchers feel the 1989 Neptune flyby — Voyager’s final planetary encounter — might have offered a preview of what’s to come next summer. Scientists suggest that Triton, with its icy surface, bright poles, varied terrain and cryovolcanoes, is a Pluto-like object that Neptune pulled into orbit. Scientists recently restored Voyager’s footage of Triton and used it to construct the best global color map of that strange moon yet — further whetting appetites for a Pluto close-up.

“There is a lot of speculation over whether Pluto will look like Triton, and how well they’ll match up,” McNutt said. “That’s the great thing about first-time encounters like this — we don’t know exactly what we’ll see, but we know from decades of experience in first-time exploration of new planets that we will be very surprised.”

Similar to Voyager 1 and 2’s historic observations, New Horizons also is on a path toward potential discoveries in the Kuiper Belt, which is a disc-shaped region of icy objects past the orbit of Neptune, and other unexplored realms of the outer solar system and beyond.

“No country except the United States has the demonstrated capability to explore so far away,” said Stern. “The U.S. has led the exploration of the planets and space to a degree no other nation has, and continues to do so with New Horizons. We’re incredibly proud that New Horizons represents the nation again as NASA breaks records with its newest, farthest and very capable planetary exploration spacecraft.”

Voyager 1 and 2 were launched 16 days apart in 1977, and one of the spacecraft visited Jupiter, Saturn, Uranus and Neptune. Voyager 1 now is the most distant human-made object, about 12 billion miles (19 billion kilometers) away from the sun. In 2012, it became the first human-made object to venture into interstellar space. Voyager 2, the longest continuously operated spacecraft, is about 9 billion miles (15 billion kilometers) away from our sun.

New Horizons is the first mission in NASA’s New Frontiers program. APL manages the mission for NASA’s Science Mission Directorate at NASA Headquarters. APL also built and operates the New Horizons spacecraft.

The Voyager spacecraft were built and continue to be operated by NASA’s Jet Propulsion Laboratory in Pasadena, California. The Voyager missions are part of NASA’s Heliophysics System Observatory, sponsored by the Heliophysics Division of the Science Mission Directorate.

To view the Neptune images taken by New Horizons and learn more about the mission, visit:

http://www.nasa.gov/newhorizons

For more information about the Voyager spacecraft, visit:

http://www.nasa.gov/voyager

A Decade of Discovery in Saturn’s System: The Great Cassini

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It is sometimes difficult to attach an adequate number of superlatives to the Cassini probe, which is about to enter its second decade of operations in the Saturn system.  From launching the Huygens lander, to revealing Titan’s hydrocarbon seas and the ice geysers of Enceladus, Cassini has been much more than a probe.  In many ways, although it holds no crew, Cassini has been a ship of discovery which has earned a place alongside names Endeavour, Resolution and Beagle. Some of its many accomplishments are detailed in the NASA release included below.

There are two bittersweet items to this particular anniversary story.  The first is the simple fact that despite its myriad accomplishments, NASA has absolutely nothing  in the works in terms of a mission which compares favorably with Cassini, and could be considered a worthy successor to it.

Juno is on the way to Jupiter for a one year mission, and New Horizons is on the way to a flyby of Pluto next July, and after that, possibly a flyby of Kuiper belt object, but that is all it is, a flyby.  And, although NASA has received preliminary funding for a proposed “Europa Clipper” mission to Jupiter’s enigmatic moon, it likely would not launch until 2025, and even then not arriving until after a cruise of more than six years.  As of the moment, the Europa Clipper, which would in reality be orbiting Jupiter, is still likely to be a comparatively paltry solar powered spacecraft.  By comparison, Cassini is a veritable dreadnought. 

The second item is perhaps minor, possibly petty, certainly unlikely, and also probably not of great concern to many. At the end of its mission, Cassini will be sent in to a death plunge into Saturn’s atmosphere in order to prevent the extremely remote chance that it will instead crash into Titan, or perhaps another moon, and even more remotely, contaminate it with Earth borne organisms which have survived the long journey, longer stay and all that radiation.  While it will no doubt continue to send back useful data until the very last second, this ship deserves better.

NASA previously examined a number of End of Mission (EOM) options, from crashing into one of the icy Moons, to seeking a stable orbit around Titan or even a carefully engineered ejection from the Saturn system altogether with the slim possibility of a Jupiter flyby. Planetary protection issues are a noteworthy precaution, but sometimes it seems NASA has an altogether unholy fascination with destroying the objects it creates. Perhaps its the whole V’Ger thing.

One wishes NASA might have elected to leave Cassini in a stable orbit,  awaiting the day we can retrieve the history making craft and and provide her a proper home, either back on Earth, or in some yet to be envisioned orbital museum. Far fetched perhaps, but consider the implication. Is our confidence in humanity’s future in space so low that the certainty of destruction is preferable?

NASA News Story

It has been a decade since a robotic traveler from Earth first soared over rings of ice and fired its engine to fall forever into the embrace of Saturn. On June 30, the Cassini mission will celebrate 10 years of exploring the planet, its rings and moons.
The Cassini spacecraft, carrying the European Space Agency’s Huygens probe, arrived in the Saturn system on June 30, 2004, for a four-year primary mission. Since 2008, NASA has granted the mission three extensions, allowing scientists an unprecedented opportunity to observe seasonal changes as the planet and its retinue completed one-third of their nearly 30-year-long trek around the sun.

“Having a healthy, long-lived spacecraft at Saturn has afforded us a precious opportunity,” said Linda Spilker, Cassini project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California. “By having a decade there with Cassini, we have been privileged to witness never-before-seen events that are changing our understanding of how planetary systems form and what conditions might lead to habitats for life.”

After 10 years at Saturn, the stalwart spacecraft has beamed back to Earth hundreds of gigabytes of scientific data, enabling the publication of more than 3,000 scientific reports. Representing just a sampling, 10 of Cassini’s top accomplishments and discoveries are:

— 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

“It’s incredibly difficult to sum up 10 extraordinary years of discovery in a short list, but it’s an interesting exercise to think about what the mission will be best remembered for many years in the future,” Spilker said.

Further details about each of these top-10 discoveries are available at:

http://saturn.jpl.nasa.gov/news/cassinifeatures/10thannivdiscoveries/

In celebration of the 10th anniversary, members of the Cassini team selected some of their favorite images for a gallery, describing in their own words what makes the images special to them. The gallery is available at:

http://saturn.jpl.nasa.gov/news/cassinifeatures/10thannivimages/

While Cassini was originally approved for a four-year study of the Saturn system, the project’s engineers and scientists had high hopes that the mission might carry on longer, and designed the system for endurance. The spacecraft has been remarkably trouble-free, and from an engineering standpoint, the main limiting factor for Cassini’s lifetime now is how much propellant is left in its tanks. The mission owes a great deal of its longevity to skillful and efficient piloting by the mission’s navigation and operations teams.

“Our team has done a fantastic job optimizing trajectories to save propellant, and we’ve learned to operate the spacecraft to get the most out of it that we possibly can,” said Earl Maize, Cassini project manager at JPL. “We’re proud to celebrate a decade of exploring Saturn, and we look forward to many discoveries still to come.”

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, Pasadena, manages the mission for NASA’s Science Mission Directorate in Washington.

A Glowing Red Nebula and Uranus Seen Through Saturn’s Rings

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Image Credit: ESO

The European Southern Observatory at La Silla released this image of a glowing hydrogen cloud, or nebula, Gum 41. The glow is caused by the searing radiation emitted by young, very hot stars which excites the hydrogen gas left over from star formation.

This nebula is in the constellation Centaurus in the southern sky, approximately 7,300 light years away.

According to ESO, GUM 41 is actually quite faint, and the image was aided by the use of a filter to pick out the red glow against the background of space.

Much closer to home, there was this, Uranus as seen from the Cassini spacecraft orbiting Saturn

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From the JPL story:

“When this view was obtained, Uranus was nearly on the opposite side of the sun as seen from Saturn, at a distance of approximately 28.6 astronomical units from Cassini and Saturn. An astronomical unit is the average distance from Earth to the sun, equal to 93 million miles (150 million kilometers). At their closest – once during each Saturn orbit of nearly 30 years – the two planets approach to within about 10 astronomical units of each other.”

A rather beautiful galaxy we’ve got here.

A Multi-Layered Ocean on Ganymede

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Image credit: JPL

A fascinating news release out of JPL suggests once more just how weird and wonderful our own solar system is turning out to be. Today’s story offers speculation that Jupiter’s moon  Ganymede may have “layered” oceans in which water alternates with different tiers of ice, depending on the relative salt content. Furthermore, as with Europa, the presence of microbial life is not out of the question.

A copy of the full news release is include below, and as it reminds us at the end, Ganymede is but one of five moons in our solar system thought to have its own, very substantial ocean.  While sending astronauts to the outer planets and their moon is well outside of what we can achieve with present technology, sending robotic craft are limited by one thing…money.

One might think that a true space faring society would be hard at work figuring out a way to send probes to all of these destinations, but we are not. Instead, Alabama Senator Richard Shelby is complaining that NASA isn’t spending enough money on SLS, while continuing to rage against Commercial Crew, and in particular SpaceX.  Apparently for saving NASA too much money.

JPL New Release:

The largest moon in our solar system, a companion to Jupiter named Ganymede, might have ice and oceans stacked up in several layers like a club sandwich, according to new NASA-funded research that models the moon’s makeup.

Previously, the moon was thought to harbor a thick ocean sandwiched between just two layers of ice, one on top and one on bottom.

“Ganymede’s ocean might be organized like a Dagwood sandwich,” said Steve Vance of NASA’s Jet Propulsion Laboratory in Pasadena, Calif., explaining the moon’s resemblance to the “Blondie” cartoon character’s multi-tiered sandwiches. The study, led by Vance, provides new theoretical evidence for the team’s “club sandwich” model, first proposed last year. The research appears in the journal Planetary and Space Science.

The results support the idea that primitive life might have possibly arisen on the icy moon. Scientists say that places where water and rock interact are important for the development of life; for example, it’s possible life began on Earth in bubbling vents on our sea floor. Prior to the new study, Ganymede’s rocky sea bottom was thought to be coated with ice, not liquid — a problem for the emergence of life. The “club sandwich” findings suggest otherwise: the first layer on top of the rocky core might be salty water.

“This is good news for Ganymede,” said Vance. “Its ocean is huge, with enormous pressures, so it was thought that dense ice had to form at the bottom of the ocean. When we added salts to our models, we came up with liquids dense enough to sink to the sea floor.”

NASA scientists first suspected an ocean in Ganymede in the 1970s, based on models of the large moon, which is bigger than Mercury. In the 1990s, NASA’s Galileo mission flew by Ganymede, confirming the moon’s ocean, and showing it extends to depths of hundreds of miles. The spacecraft also found evidence for salty seas, likely containing the salt magnesium sulfate.

Previous models of Ganymede’s oceans assumed that salt didn’t change the properties of liquid very much with pressure. Vance and his team showed, through laboratory experiments, how much salt really increases the density of liquids under the extreme conditions inside Ganymede and similar moons. It may seem strange that salt can make the ocean denser, but you can see for yourself how this works by adding plain old table salt to a glass of water. Rather than increasing in volume, the liquid shrinks and becomes denser. This is because the salt ions attract water molecules.

The models get more complicated when the different forms of ice are taken into account. The ice that floats in your drinks is called “Ice I.” It’s the least dense form of ice and lighter than water. But at high pressures, like those in crushingly deep oceans like Ganymede’s, the ice crystal structures become more compact. “It’s like finding a better arrangement of shoes in your luggage — the ice molecules become packed together more tightly,” said Vance. The ice can become so dense that it is heavier than water and falls to the bottom of the sea. The densest and heaviest ice thought to persist in Ganymede is called “Ice VI.”

By modeling these processes using computers, the team came up with an ocean sandwiched between up to three ice layers, in addition to the rocky seafloor. The lightest ice is on top, and the saltiest liquid is heavy enough to sink to the bottom. What’s more, the results demonstrate a possible bizarre phenomenon that causes the oceans to “snow upwards.” As the oceans churn and cold plumes snake around, ice in the uppermost ocean layer, called “Ice III,” could form in the seawater. When ice forms, salts precipitate out. The heavier salts would thus fall downward, and the lighter ice, or “snow,” would float upward. This “snow” melts again before reaching the top of the ocean, possibly leaving slush in the middle of the moon sandwich.

“We don’t know how long the Dagwood-sandwich structure would exist,” said Christophe Sotin of JPL. “This structure represents a stable state, but various factors could mean the moon doesn’t reach this stable state.

Sotin and Vance are both members of the Icy Worlds team at JPL, part of the multi-institutional NASA Astrobiology Institute based at the Ames Research Center in Moffett Field, Calif.

The results can be applied to exoplanets too, planets that circle stars beyond our sun. Some super-Earths, rocky planets more massive than Earth, have been proposed as “water worlds” covered in oceans. Could they have life? Vance and his team think laboratory experiments and more detailed modeling of exotic oceans might help find answers.

Ganymede is one of five moons in our solar system thought to support vast oceans beneath icy crusts. The other moons are Jupiter’s Europa and Callisto and Saturn’s Titan and Enceladus. The European Space Agency is developing a space mission, called JUpiter ICy moons Explorer or JUICE, to visit Europa, Callisto and Ganymede in the 2030s. NASA and JPL are contributing to three instruments on the mission, which is scheduled to launch in 2022 (see http://www.jpl.nasa.gov/news/news.php?release=2013-069).

Other authors of the study are Mathieu Bouffard of Ecole Normale Supérieure de Lyon, France, and Mathieu Choukroun, also of JPL and the Icy World team of the NASA Astrobiology Institute. JPL is managed by the California Institute of Technology in Pasadena for NASA.

 

Cassini Data Suggests Enceladus Has a Subsurface Ocean

enceladusocean

Image Credit: NASA/JPL-Caltech

The treasure trove which is the Cassini spacecraft orbiting the Saturn system continues to produce fascinating discoveries. Now it appears that Saturn’s moon Enceladus has a subsurface ocean, one which is likely responsible for the geysers which Enceladus is jetting into space.

It is important to note that after the end of the Cassini mission, NASA has nothing else planned for this amazing system, one which offers an ever widening number of targets worthy of further exploration. Much the same could be said for Jupiter’s system as well, which will at least be visited by the short lived Juno orbiter, even as notional funding for a Europa mission is barely enough to keep the lights on.

One wonders what it would take to inspire a new major outer planets mission.

The full text of the NASA press release is below:

NASA’s Cassini spacecraft and Deep Space Network have uncovered evidence Saturn’s moon Enceladus harbors a large underground ocean of liquid water, furthering scientific interest in the moon as a potential home to extraterrestrial microbes.

Researchers theorized the presence of an interior reservoir of water in 2005 when Cassini discovered water vapor and ice spewing from vents near the moon’s south pole. The new data provide the first geophysical measurements of the internal structure of Enceladus, consistent with the existence of a hidden ocean inside the moon. Findings from the gravity measurements are in the Friday April 4 edition of the journal Science.

“The way we deduce gravity variations is a concept in physics called the Doppler Effect, the same principle used with a speed-measuring radar gun,” said Sami Asmar of NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif., a coauthor of the paper. “As the spacecraft flies by Enceladus, its velocity is perturbed by an amount that depends on variations in the gravity field that we’re trying to measure. We see the change in velocity as a change in radio frequency, received at our ground stations here all the way across the solar system.”

The gravity measurements suggest a large, possibly regional, ocean about 6 miles (10 kilometers) deep, beneath an ice shell about 19 to 25 miles (30 to 40 kilometers) thick. The subsurface ocean evidence supports the inclusion of Enceladus among the most likely places in our solar system to host microbial life. Before Cassini reached Saturn in July 2004, no version of that short list included this icy moon, barely 300 miles (500 kilometers) in diameter.

“This then provides one possible story to explain why water is gushing out of these fractures we see at the south pole,” said David Stevenson of the California Institute of Technology, Pasadena, one of the paper’s co-authors.

Cassini has flown near Enceladus 19 times. Three flybys, from 2010 to 2012, yielded precise trajectory measurements. The gravitational tug of a planetary body, such as Enceladus, alters a spacecraft’s flight path. Variations in the gravity field, such as those caused by mountains on the surface or differences in underground composition, can be detected as changes in the spacecraft’s velocity, measured from Earth.

The technique of analyzing a radio signal between Cassini and the Deep Space Network can detect changes in velocity as small as less than one foot per hour (90 microns per second). With this precision, the flyby data yielded evidence of a zone inside the southern end of the moon with higher density than other portions of the interior.

The south pole area has a surface depression that causes a dip in the local tug of gravity. However, the magnitude of the dip is less than expected given the size of the depression, leading researchers to conclude the depression’s effect is partially offset by a high-density feature in the region, beneath the surface.

“The Cassini gravity measurements show a negative gravity anomaly at the south pole that however is not as large as expected from the deep depression detected by the onboard camera,” said the paper’s lead author, Luciano Iess of Sapienza University of Rome. “Hence the conclusion that there must be a denser material at depth that compensates the missing mass: very likely liquid water, which is seven percent denser than ice. The magnitude of the anomaly gave us the size of the water reservoir.”

There is no certainty the subsurface ocean supplies the water plume spraying out of surface fractures near the south pole of Enceladus, however, scientists reason it is a real possibility. The fractures may lead down to a part of the moon that is tidally heated by the moon’s repeated flexing, as it follows an eccentric orbit around Saturn.

Much of the excitement about the Cassini mission’s discovery of the Enceladus water plume stems from the possibility that it originates from a wet environment that could be a favorable environment for microbial life.

“Material from Enceladus’ south polar jets contains salty water and organic molecules, the basic chemical ingredients for life,” said Linda Spilker, Cassini’s project scientist at JPL. “Their discovery expanded our view of the ‘habitable zone’ within our solar system and in planetary systems of other stars. This new validation that an ocean of water underlies the jets furthers understanding about this intriguing environment.”

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL manages the mission for NASA’s Science Mission Directorate in Washington. For more information about Cassini, visit:

http://www.nasa.gov/cassini