Tag Archives: cassini spacecraft

Image credits: NASA/JPL

New ‘Mystery Islands’ found on Titan’s Methane Sea

The enduring Cassini spacecraft returns with new insight into the hydrocarbon seas from Saturn’s moon Titan. The latest findings were reported after the spacecraft’s most recent flyby above Titan’s northern hemisphere on August 21, where it performed observations of the largest liquid methane/ethane sea, the 400,000 square kilometre Kraken Mare. The Cassini astronomers were looking to probe the methane sea’s depths, but meanwhile they come across something more interesting: strange floating features reminiscent of the “Magic Island” found on Ligeia Mare, another large methane sea.

Bright features on a huge sea of liquid methane

In contrast to a previously reported bright, mystery feature called “Magic Island” in another of Titan’s large seas, Ligeia Mare, these new features were observed with both  radar data and images from Cassini’s Visible and Infrared Mapping Spectrometer (VIMS). Because the researchers have two different data sets at two different wavelengths this will help them better assess what these mysterious features represent. So far, the VIMS data suggests these features might be waves or floating debris.

Mystery island

Cassini’s radar instrument images show that a bright feature appeared in Kraken Mare, Titan’s largest sea.
Image Credit: NASA/JPL-Caltech/ASI/Cornell

Ligeia Mare’s Magic Island was first discovered in July 2013,  covering an area of some 260 square kilometres. During another flyby in August 2013, data from the Synthetic Aperture Radar (SAR) showed that Magic Island was still there yet the bright features had evolved. Clearly, Cassini shows that Titan’s polar seas are extremely dynamic and hold many mysteries. More observations are required, but our next shot won’t be until January 2015, when Cassini is scheduled to observe the original “magic island” feature in Ligeia Mare once more.

On another note, just last week the same Cassini team put a huge grin up all our faces when they release some stunning photos of light bouncing off Titan’s atmosphere. Here are two of the best shots:

Image credits: NASA/JPL

Image credits: NASA/JPL

Another image from Cassini’s Visual and Infrared Mapping Spectrometer on July 24, 2012, showing a sunlight reflection on a Titanian sea. Image credits: Barnes et al./NASA/JPL/University of Arizona

Another image from Cassini’s Visual and Infrared Mapping Spectrometer on July 24, 2012, showing a sunlight reflection on a Titanian sea. Image credits: Barnes et al./NASA/JPL/University of Arizona

A shallow extraterrestrial sea

During this most recent flyby, Cassini also probed the depths of Kraken Mare. The spacecraft collect altimetry (or height) data, using the spacecraft’s radar instrument along a 120-mile (200-kilometer) shore-to-shore track of Kraken Mare. Reflections were isolated for a shallow 40 km segment. The distinctive double-peaked returns from a region near the mouth of a flooded river valley that feeds the sea indicates liquid methane depths of 20-35 m. For the remainder of 160 km, no observations could be made. The signal most likely became skewed because the liquid was more absorbing than Ligeia Mare or the depths were too high (greater than 200m). For comparison, central Ligeia Mare was 160 m deep. It should be interesting to see how deep Kraken Mare is off-coast.

Cassini radar data reveal the depth of a liquid methane/ethane sea on Saturn's moon Titan near the mouth of a large, flooded river valley. Image Credit: NASA/JPL-Caltech/ASI/Cornell

Cassini radar data reveal the depth of a liquid methane/ethane sea on Saturn’s moon Titan near the mouth of a large, flooded river valley.
Image Credit: NASA/JPL-Caltech/ASI/Cornell

Learn more at NASA’s Cassini mission homepage.

 

 

 

Ocean discovered on Enceladus may be best place to look for alien life

Earth is not the only place in the solar system to hold watery oceans: Enceladus, one of Saturn’s moons also holds a liquid ocean, albeit one that is covered by ice. However, Enceladus is still an extremely exciting place to find extraterrestrial life – not only because of the water it holds, but because water is in contact with the moon’s rocky core, so elements useful for life, such as phosphorus, sulfur and potassium, will leach into the ocean – making it a potential habitat for life.

An artist’s impression of the interior of Saturn’s moon Enceladus. Credits: Nasa/JPL-Caltech.

Enceladus is the sixth-largest of the moons of Saturn, with a mean radius of 252 km (156 miles). In 2005, the Cassini spacecraft spotted what appeared to be plumes of water shooting into space from cracks in the icy surface of Enceladus. The only reasonable explanation would be that the moon has an ocean of liquid water under the ice. Now, a team led by Luciano Iess of the University of Rome confirmed that the ocean exists, and also showed that, like Earth’s, it doesn’t cover the entire surface.

But how could a salty liquid ocean exist, under ice, in Saturn’s area – so far away from the Sun? The likely cause is gravity: as the moon moves around Saturn, tidal forces from the planet and the other moons flex and bend the core of the planet, creating friction – therefore heat. This melts the ice, maintaining a liquid ocean.

Gravitational measurements made by the Cassini spacecraft revealed that a 10km-deep ocean of water, larger than Lake Superior, lurks beneath the icy surface of Enceladus at the moon’s south pole; the liquid ocean reduces the volume of the southern hemisphere, so judging by the larger volume of the northern hemisphere, it’s likely that the ocean can only be found in the southern areas.

David Stevenson, a planetary scientist at the California Institute of Technology in Pasadena, said the body of water was so large it “may extend halfway or more towards the equator in every direction. It might even extend all the way to the north.”

So what does this mean? Is it far fetched to think that Enceladus could host life? No, not really. There are clear indications that it is habitable – the temperature is right, you get liquid water, and you get some important chemical elements for life, so Enceladus might be the perfect place to look for life (probably microscopic life).

“The question is what conditions do you need to form life and, of course, we don’t know what temperature the ocean is today, nor do we know what it was back in the geological past. But it’s conceivable that it was warm enough, with circulation of water coming from the silicate core as well, to allow life to form even if today that ocean is maintained by antifreeze and is slightly below the freezing point,” said Jonathan Lunine, a member of the team at Cornell University in New York. The antifreeze in question is salt, which reduces the temperature at which water freezes.

Enceladus is not the only moon which sports a liquid water the ice: we’ve written several articles about Europa, a moon of Saturn, and how promising it is. Europa has a more extensive, global ocean under the surface – it is regarded by many as the most likely place to host life in our solar system (bar Earth). But Enceladus also has researchers rubbing their hands due to its vapour plumes from the south pole which also contain organic molecules – possible, but not clear signs of life.

To me, the next step here is to establish permanent satellites around Europa and Enceladus, and gather as much geological information as possible, and in time (why not?) land a rover there. The main problem, is, of course, the funding.

Chris McKay, an astrobiologist at Nasa’s Ames Research Centre in California, said:

“There are now several lines of evidence – the geysers, the plume chemistry, and now gravity – that indicate a substantial body of liquid water. For astrobiology this is confirmation of what we expected and is good news. My one view is that Enceladus should be the priority.”

 

 

 

 

Chris McKay, an astrobiologist at Nasa’s Ames Research Centre in California, said: “There are now several lines of evidence – the geysers, the plume chemistry, and now gravity – that indicate a substantial body of liquid water. For astrobiology this is confirmation of what we expected and is good news. My one view is that Enceladus should be the priority.”

Ingredient of Household Plastic Found on Saturn Moon

NASA’s Cassini spacecraft has detected propylene, a chemical used greatly in everyday life, in things like food-storage containers, car bumpers and other consumer products, on Saturn’s Moon Titan. I really recommend watching the video below, as it explains the situation in great detail:

A small amount of propylene was identified in Titan’s lower atmosphere by Cassini’s Composite Infrared Spectrometer (CIRS); the device measures infrared emissions given away by Saturn and Saturn’s moons in a similar way to the way our hands feel a fire’s warmth. Every gas has a unique thermal fingerprint, and based on that, CIRS can identify pretty much every gas. The only problem is isolating the signal from other, interfering signals.

“This measurement was very difficult to make because propylene’s weak signature is crowded by related chemicals with much stronger signals,” said Michael Flasar, Goddard scientist and principal investigator for CIRS. “This success boosts our confidence that we will find still more chemicals long hidden in Titan’s atmosphere.”

This detection brings a valuable piece of the puzzle, a piece which was sought after since the Voyager 1 spacecraft and the first-ever close flyby of this moon in 1980. Voyager identified many of the gases in Titan’s hazy brownish atmosphere as hydrocarbons, a class of organic chemical compounds composed only of the elements carbon (C) and hydrogen (H) which compose most of the petroleum and natural gas.

False-color images, made from data obtained by NASA's Cassini spacecraft, shows clouds covering parts of Saturn's moon Titan in yellow.

False-color images, made from data obtained by NASA’s Cassini spacecraft, shows clouds covering parts of Saturn’s moon Titan in yellow.

In Titan’s atmosphere, hydrocarbons form after sunlight breaks apart methane, the second-most plentiful gas in that atmosphere. The new fragments can bond together, forming chains of 2, 3, or even more carbons – ethane and propane for example, can be created this way.

As Cassini continued to discover more and more hydrocarbons on Titan, propylene remained elusive until the CIRS analysis.

“I am always excited when scientists discover a molecule that has never been observed before in an atmosphere,” said Scott Edgington, Cassini’s deputy project scientist at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif. “This new piece of the puzzle will provide an additional test of how well we understand the chemical zoo that makes up Titan’s atmosphere.”

For more information on the Cassini mission, visit NASA’s page.

Via NASA.

Cassini Spies Bright Venus From Saturn Orbit

cassini 1

This is a true-color picture of Saturn and Venus. The bright arc is the limb of Saturn. A portion of the rings is seen in silhouette against the face of Saturn, which itself is faintly illuminated by sunlight scattered off the rings.

I’m an absolute fan of the Cassini spacecraft – this is hands down my favorite mission. I mean, it’s been providing us incredibly valuable information for years now, in a very interesting area of our solar system, the Jupiter-Saturn area. This mission is one of the main reasons why we now believe places like Europa to be the most likely place to host life in our solar system. Now, NASA’s Cassini spacecraft spied the bright, cloudy terrestrial planet, Venus.

Venus, the long lost brother of our planet; even with an atmosphere of carbon dioxide that reaches nearly 900 degrees Fahrenheit (500 degrees Celsius) and a surface pressure 100 times that of Earth’s, it is considered a twin to our planet because of similar masses, sizes, rocky compositions, etc. The reason why Venus is so bright and spectacular to look at is that it’s covered in thick sulfuric acid clouds.

cassini 2

Images taken using red, green and blue spectral filters were combined to create this natural color view.

Cassini took many spectacular photos so far, and this ones aren’t the exception. Last November, because the Cassini spacecraft was in the shadow of Saturn, it was able to “look” in the direction of Venus and the Sun, taking a backlit image of Saturn and its rings in a particular viewing geometry called “high solar phase. This relative position reveals details about the rings and Saturn’s atmosphere that cannot be seen in lower solar phase.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. For more information, you might want to visit its website and the JPL website.

Via NASA.

Cassini sheds light on cosmic particle accelerators

During a chance encounter with an unusually strong blast of solar wind at Saturn, NASA’s Cassini spacecraft detected particles being accelerated to ultra-high energies (like those at the LHC); this acceleration is similar to that which takes place around distant supernovas and provides a valuable in-situ study environment.

cassini saturn

The Cassini spacecraft is an absolutely stunning evergreen source of information. Since we can’t exactly travel to distant supernovas and study this phenomena up close, the spacecraft provided a unique opportunity to observe this phenomenon up-close. The findings, published this week in the journal Nature Physics, confirm that certain kinds of shocks can become considerably more effective electron accelerators than previously thought.

Shockwaves are probably more common in space than you’d expect. The aftermath of a stellar explosion, for example, creates a huge shockwave accelerating the debris outward, just like the flow of particles from the sun (the solar wind) does when it reaches the magnetic field of a planet, forming a bow shock. Depending on the magnetic orientation and the strength of the shock, particles can be accelerated to close to the speed of light at these boundaries. These may actually be the dominant source of cosmic rays, high-energy particles that pervade our galaxy.

Researchers are most interested in what they call “quasi-parallel” shocks: where the magnetic field and the “forward”-facing direction of the shock are almost aligned – a good example of this is in supernova remnants. In this new study, Adam Masters of the Institute of Space and Astronautical Science, Sagamihara, Japan, describes the first detection of significant acceleration of electrons in a quasi-parallel shock at Saturn, coinciding with what may very well be the strongest shock ever encountered by researchers at the planet.

“Cassini has essentially given us the capability of studying the nature of a supernova shock in situ in our own solar system, bridging the gap to distant high-energy astrophysical phenomena that are usually only studied remotely,” said Masters.

Interestingly enough, this could provide useful information for particle physics, providing once again an example how phenomenas taking place at the largest of scales are tightly connected to those taking place in the subatomic universe.

Via NASA

Iapetus – the black-and-white walnut Moon

Iapetus is the third largest moon of Saturn, with a radius of about 42% that of our moon, and a mass that weighs up to only 2.5%. But Iapetus has a number of shocking features, unique throughout the entire solar system.

The Walnut Moon

walnut moon

This is the equatorial ridge that  runs along the center of Cassini Regio; in case you were wondering, the ridge has an average height of 13 km, occasionally going up to 20km, a length of 1,300 km and a width of about 20 km. It was discovered when the Cassini spacecraft imaged Iapetus on December 31, 2004, and even in 2013, it has astronomers baffled. Why did it form and why does it follow the equator so closely, no one knows for sure, though there are three competing theories:

1. The ridge could be a remnant of the oblate shape of the young Iapetus, when it was rotating more rapidly than it does today, but if this were to be true, for reasons you can read here, this would mean that the moon was formed much earlier than previously believed.

2. The ridge could be icy material that welled up from beneath the surface and then solidified – this hypothesis requires that rotational axis would have been driven to its current position by the ridge.

3. Iapetus could have had a ring system during its formation and the ridge is actually an accretion of that material. However, the ridge appears too solid to be the result of a collapsed ring, and images show tectonic faults crossing the ridge, so this seems highly unlikely.

The likelihood of any theory is not striking, and the matter is still a hot topic among some astronomic circles.

Black and white

iapetus bright

In the 17th century, Giovanni Cassini observed that he could see Iapetus only on the west side of Saturn and he could never see it on the east. So Cassini, the bright man that he was, deducted that Iapetus is locked in synchronous rotation about Saturn (much like the Moon is to the Earth) and that one side is darker than the other. Centuries passed until actual images confirmed this man’s deduction, but Cassini wasn’t able to explain why this is.

The difference is striking – the leading hemisphere and sides are dark while most of the trailing hemisphere and poles are bright. To make it even more puzzling, when the Cassini spacecraft passed at only 1640 km from Iapetus, it showed that both hemispheres are heavily cratered.

Now, NASA researchers believe the dark material is a lag (residue) from the sublimation (evaporatio

iapetus darkn) of water ice on the surface of Iapetus, possibly darkened by exposure to sunlight. Another possibility is that the front hemisphere is gathering brighter matter, much like your windshield gathers most of the dust, leaving the back of the car cleaner.

 

Iapetus has been imaged multiple times from moderate distances by the Cassini orbiter, but due to its distance to Saturn, close observation remains difficult; no near future flybys are planned, but a viewing opportunity will be possible 2 years from now.

Saturnian storm caught choking on its own tail

The Uroburos is a mythological symbol representing a serpent or dragon eating its own tail – a symbol of cyclicality and eternal return. The Cassini spacecraft watching Saturn recently caught a glimpse of a storm that looks remarkably like the mythological creature – only it choked on its own tail.

saturn

This mosaic of false-color images from NASA’s Cassini spacecraft shows what a giant storm in Saturn’s northern hemisphere looked like about a month after it began. The bright head of the storm is on the left. Via NASA.

The storm came out incredibly violent, churned around the planet until it made it to the other side and back again, choking on its own tail.

“This Saturn storm behaved like a terrestrial hurricane – but with a twist unique to Saturn,” said Andrew Ingersoll, a Cassini imaging team member based at the California Institute of Technology, Pasadena, who is a co-author on the new paper in the journal Icarus. “Even the giant storms at Jupiter don’t consume themselves like this, which goes to show that nature can play many awe-inspiring variations on a theme and surprise us again and again.”

Earth’s hurricanes typically feed off energy from warmer waters, leaving behind a cold-water wake – this storm in Saturn’s northern hemisphere also feasted off warm “air” in the gas giant’s atmosphere in a similar fashion. From what we know of however, terrestrial storms have never encountered their own wakes – they stumble upon topographic features such as mountains and are blocked by them. The bright, turbulent storm head was able to stomp a path all the way across the planet, and it was only when it ran into itself again that it stopped.

saturn2

This is also a mosaic of false color.

“This thunder-and-lightning storm on Saturn was a beast,” said Kunio Sayanagi, the paper’s lead author and a Cassini imaging team associate at Hampton University in Virginia. “The storm maintained its intensity for an unusually long time. The storm head itself thrashed for 201 days, and its updraft erupted with an intensity that would have sucked out the entire volume of Earth’s atmosphere in 150 days. And it also created the largest vortex ever observed in the troposphere of Saturn, expanding up to 7,500 miles [12,000 kilometers] across.”

Every Saturn year (~30 Earth years), massive storms occur – but this one was definitely the largest in that period.

“Cassini’s stay in the Saturn system has enabled us to marvel at the power of this storm,” said Scott Edgington, Cassini‘s deputy project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “We had front-row seats to a wonderful adventure movie and got to watch the whole plot from start to finish. These kinds of data help scientists compare weather patterns around our solar system and learn what sustains and extinguishes them.”

Via NASA

Tectonics on Enceladus

As you may or may not know, we’ve launched a new section of our website: Science Questions and Answers – a section aimed at you guys, where you can ask all questions science-related, and share your knowledge with others. We’re still in the beta version, but please, feel free to ask away – we’ll do our best to answer, answer, and vote.

So recently, somebody asked about tectonics on Enceladus. How does tectonics even work on a satellite like Enceladus? Well…

Plate tectonics

plate tectonics

Plate tectonics is a theory that emerged in the 1970s, as an attempt to describe the large-scale motions of Earth’s lithosphere. Basically, the litosphere of the Earth is composed of distinct rigid plates, comprising of continental crust or oceanic crust. These plates are in a continuous relative movement.

enceladus tectonics 1

Plate tectonics is, at its very basic level, a kinematic phenomenon. Generally, it is accepted that tectonic plates are able to move because of the relative density of oceanic lithosphere and the relative weakness of the asthenosphere, but there is still a lot of debate here. The energy is provided by dissipation of heat from the mantle through convection currents; how mantle convection relates directly and indirectly to the motion of the plates is a matter of ongoing study and discussion in geodynamics.

Enceladus tectonics

enceladus tectonics 2

Enceladus is a moon of Saturn, with a mean diameter of 505 kilometers, seven times smaller than the Earth’s Moon; it is covered in ice, but seems to have considerable amounts of water beneath its frozen surface. The surface is so cold that instead of traditional volcanoes, the surface of Enceladus is riddled with cryovolcanoes – volcanoes that erupt volatiles such as water, ammonia or methane, instead of molten rock.

Voyager 2 provided the first signs of tectonics on Enceladus; troughs, scarps, and belts of grooves and ridges were all observed. Perhaps the most shocking evidence was rifts; a rift is a linear zone where the litosphere is being bulled apart by tectonic forces. Observed canyons are up to 200 km long, 5–10 km wide, and one km deep. These features are relatively young and seem active.

Another evidence of tectonics is the grooved terrain; the surface of Enceladus is scarred with curvilinear grooves and ridges which often separate smooth areas from impact craters. Other tectonic features include numerous fractures on the surface of the moon. All in all, the geodynamic evidence is pretty convincing, but there’s even more.

enceladus stripes

Recent data from the Cassini spacecraft highlighted, aside from the prominent tectonic features, intense heat flow and geyser like plumes. Therefore, in the deeps of Enceladus, there lies a significant source of heat. Even a tiny, icy moon like Enceladus can develop complex surficial geomorphologies, high heat fluxes, and geyser-like activity, even without convection currents – which raises an interesting discussion about Earth’s tectonics, but that’s a different story.

Exobiology implications

Not entirely related to the question… but. If the satellite has a hot core and an icy surface, it’s only logical that it has a liquid water habitat inside, which is actually quite likely to host life! Researchers and exobiologists in particular are speculating a lot on this matter, and Enceladus is one of the top candidates for extraterrestrial life in our solar system.

Saturn rings

A black and white view of Saturn shadowed by its rings [SCIENCE ART]

In a dazzling new photo delivered by NASA’s Cassini spacecraft, Saturn can be admired in new black and white perspective, as its southern reaches are draped in the shadow of the huge planet’s rings.

Saturn rings

The near-infrared photo was snapped on June 15 by the Cassini probe, a spacecraft launched in 1997 part of an international collaborative effort and which since its arrival in 2004 has been surveying Saturn and its satellites. At the time of the photo being taken, Cassini  was about 1.8 million miles (2.9 million kilometers) from Saturn at the time. The image scale is 11 miles (17 km) per pixel.

The small dot on the far left corner lies the moon Enceladus.

NASA's Cassini mission show river networks draining into lakes in Titan's north polar region. (c) NASA/JPL/USGS

Scientists propose space boat that paddles through Titan’s methane lakes

NASA's Cassini mission show river networks draining into lakes in Titan's north polar region. (c) NASA/JPL/USGS

NASA’s Cassini mission show river networks draining into lakes in Titan’s north polar region. (c) NASA/JPL/USGS

Rovers, like Curiosity, have been great for gathering samples and studying the terrain and atmosphere of distant worlds, but what about environments less favorable to wheeled machines? An interesting concept has been unveiled recently, in which scientists propose landing a sort of robotic boat on Titan’s largest methane lake, in order to have a physical probe on its surface.

Titan is the largest of Saturn’s more than 60 natural satellites – larger than Mercury itself. For a long time, thanks to its thick atmosphere, astronomers have viewed Titan as a worthy candidate for harboring extraterrestrial life, despite its freezing cold surface temperatures, as low as -289°F. Its significant source of liquids, however, might allow for microbial life to foster, as Titan’s covered in a slew of seas, lakes and rivers of methane.

Previously in 2005, the European Space Agency Huygens probe touchdown on land on Titan and transmitted data for a few hours before going dark, confirming satellite observations of liquid hydrocarbon deposits on the moon’s surface. Now, a  joint project of SENER and the Centro de Astrobiología in Madrid, Spain called Titan Lake In-situ Sampling Propelled Explorer (TALISE) seeks to provide a viable option for exploring Titan’s fascinating methane lakes, and search for life. The concept itself is simple, land a  boat propelled by wheels, paddles, or screws that would float around in the largest lake on the surface of Titan called Ligeia Mare. After splashing down, TALISE would make its way to the coast over the course of a trip lasting six months to a year.

“The main innovation in TALISE is the propulsion system,” Igone Urdampilleta of Spain-based private engineering firm SENER, a member of the TALISE team, said in a statement. “This allows the probe to move, under control, from the landing site in the lake, to the closest shore. The displacement capability would achieve the obtaining of liquid and solid samples from several scientific interesting locations on Titan’s surface such as the landing place, along the route towards the shore and finally at the shoreline.”

Proposed concept for the TALISE mission shows a boat propelled by paddles to travel though Titan's largest lake. (c) SENER

Proposed concept for the TALISE mission shows a boat propelled by paddles to travel though Titan’s largest lake. (c) SENER

It’s likely that the TALISE will never see the light of day, even here on Earth, however it’s serves as an interesting concept for future Titan missions, if it gets picked up by a major space agency. The scientists involved in the project proposed their concept on Sept. 27 at the European Planetary Science Congress in Madrid.

via space.com

Cassini reveals spectacular pictures of Saturn and Titan – its largest moon [shorties]

Cassini has sent some new remarkable pictures which brilliantly illustrate the difference in size between Saturn and Titan, its largest moon.

Saturn and Titan. Click the picture for full resolution

Saturn dwarfs its moon easily, even though Titan, at 3,200 miles across, is bigger than Earth’s moon, which has a diameter of only 2159 miles. If you look really closely above Saturn’s rings, there is a barely visible whitish speck – the much smaller Prometheus moon, which is only 53 miles in diameter.

Saturn and its rings

Saturn and its rings

Cassini sent numerous remarkable pictures with Saturn and its rings, and this one definitely deserves to be at the top shelf. The rings are made of mostly of pieces of water ice, the remains of comets, asteroids or other shattered moons. The Cassini mission has twice been extended due to its numerous successes and the utility (and beauty) of the data it keeps sending.