NASA Cassini sunny Hydrocarbon seas on Titan

This near-infrared, colour mosaic from NASA's Cassini spacecraft shows the sun glinting off of Titan's north polar seas.

While Cassini has captured, separately, views of the polar seas and the sun glinting off of them in the past, this is the first time both have been seen together in the same view.

The sunglint, also called a specular reflection, is the bright area near the 11 o'clock position at upper left.

This mirror-like reflection, known as the specular point, is in the south of Titan's largest sea, Kraken Mare, just north of an island archipelago separating two separate parts of the sea.

This particular sunglint was so bright as to saturate the detector of Cassini's Visual and Infrared Mapping Spectrometer (VIMS) instrument, which captures the view.

It is also the sunglint seen with the highest observation elevation so far, the sun was a full 40 degrees above the horizon as seen from Kraken Mare at this time, much higher than the 22 degrees seen in PIA18433.

Because it was so bright, this glint was visible through the haze at much lower wavelengths than before, down to 1.3 microns.

The southern portion of Kraken Mare (the area surrounding the specular feature toward upper left) displays a "bathtub ring," a bright margin of evaporate deposits, which indicates that the sea was larger at some point in the past and has become smaller due to evaporation.

The deposits are material left behind after the methane & ethane liquid evaporates, somewhat akin to the saline crust on a salt flat.

The highest resolution data from this flyby, the area seen immediately to the right of the sunglint, cover the labyrinth of channels that connect Kraken Mare to another large sea, Ligeia Mare.

Ligeia Mare itself is partially covered in its northern reaches by a bright, arrow-shaped complex of clouds.

The clouds are made of liquid methane droplets, and could be actively refilling the lakes with rainfall.

The view was acquired during Cassini's August 21, 2014, flyby of Titan, also referred to as "T104" by the Cassini team.

The view contains real colour information, although it is not the natural color the human eye would see.

Here, red in the image corresponds to 5.0 microns, green to 2.0 microns, and blue to 1.3 microns.

These wavelengths correspond to atmospheric windows through which Titan's surface is visible. The unaided human eye would see nothing but haze.

Credit: NASA/JPL-Caltech/University of Arizona/University of Idaho

Cassini captures evolution of mysterious feature in Titan sea - Video

These three images, created from Cassini Synthetic Aperture Radar (SAR) data, show the appearance and evolution of a mysterious feature in Ligeia Mare, one of the largest hydrocarbon seas on Saturn's moon Titan. 

Credit: NASA/JPL-Caltech/ASI/Cornell



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 Cassinis radar experiment, but its appearance changed between the two apparitions.

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.

Ligeia Mare on Titan. 

Credit: NASA Cassini

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 (VIMS).

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."

More information: Images of the feature taken during the Cassini flybys are available at: photojournal.jpl.nasa.gov/catalog/PIA18430

NASA’s Cassini Team: Titan Flybys Test their Talents

Cassini will attempt to bounce signals off of Saturn's moon Titan once more during a flyby on June 18, 2014, revealing important details about the moon's surface.

Image Credit: NASA/JPL-Caltech

As NASA’s Cassini spacecraft zooms toward Saturn’s smoggy moon Titan for a targeted flyby on June 18, mission scientists are excitedly hoping to repeat a scientific tour de force that will provide valuable new insights into the nature of the moon's surface and atmosphere.

For Cassini’s radio science team, the last flyby of Titan, on May 17, was one of the most scientifically valuable encounters of the spacecraft’s current extended mission.

The focus of that flyby, designated “T-101,” was on using radio signals to explore the physical nature of Titan’s vast northern seas and probe the high northern regions of its substantial atmosphere.

The Cassini team hopes to replicate the technical success of that flyby during the T-102 encounter, slated for June 18, during which the spacecraft will attempt similar measurements of Titan.

During closest approach, the spacecraft will be just 2,274 miles (3,659 kilometers) above the surface of the moon while travelling at 13,000 miles per hour (5.6 kilometers per second).

During the upcoming flyby, if all goes well as before, Cassini’s radio science subsystem will bounce signals off the surface of Titan, toward Earth, where they will be received by the ground stations of NASA’s Deep Space Network.

This sort of observation is known as a bistatic scattering experiment and its results can yield clues to help answer a variety of questions about large areas of Titan’s surface: Are they solid, slushy or liquid? Are they reflective? What might they be made of?

During the May encounter, Cassini beamed radio signals over the two largest bodies of liquid on Titan, seas named Ligeia Mare and Kraken Mare.

During that first attempt, scientists could not be certain the signals would successfully bounce off the lakes to be received on Earth.

They were thrilled when ground stations received specular reflections, essentially the glint, of the radio frequencies as they ricocheted off Titan.

Cassini team members react with excitement to the successful receipt of radio signals bounced off of Titan during a flyby on May 17, 2014. Image Credit: NASA/JPL-Caltech

Read the full story here.

Nasa Cassini Image: Surface of Titan Sea, Ligeia Mare, is mirror smooth

This false-colour image of the surface of Titan was made using radar measurements made by NASA's Cassini spacecraft. 

The spacecraft revealed that the surface of Ligeia Mare, Titan's second largest lake, is unusually still, most likely due to a lack of winds at the time of observation. 

Credit: Howard Zebker 

New radar measurements of an enormous sea on Titan offer insights into the weather patterns and landscape composition of the Saturn moon. 

The measurements, made in 2013 by NASA's Cassini spacecraft, reveal that the surface of Ligeia Mare, Titan's second largest sea, possesses a mirror-like smoothness, possibly due to a lack of winds.

"If you could look out on this sea, it would be really still. It would just be a totally glassy surface," said Howard Zebker, professor of geophysics and of electrical engineering at Stanford who is the lead author of a new study detailing the research.

Howard Zebker

The findings, recently published online in Geophysical Research Letters, also indicate that the solid terrain surrounding the sea is likely made of solid organic materials and not frozen water.

Saturn's second largest moon, Titan has a dense, planet-like atmosphere and large seas made of methane and ethane.

Measuring roughly 260 miles (420 km) by 217 miles (350 km), Ligeia Mare is larger than Lake Superior on Earth.

"Titan is the best analog that we have in the solar system to a body like the Earth because it is the only other body that we know of that has a complex cycle of solid, liquid, and gas constituents," Zebker said.

Titan's thick cloud cover makes it difficult for Cassini to obtain clear optical images of its surface, so scientists must rely on radar, which can see through the clouds, instead of a camera.

To paint a radar picture of Ligeia Mare, Cassini bounced radio waves off the sea's surface and then analyzed the echo.

The strength of the reflected signal indicated how much wave action was happening on the sea. To understand why, Zebker said, imagine sunlight reflecting off of a lake on Earth.

"If the lake were really flat, it would act as a perfect mirror and you would have an extremely bright image of the sun," he said.

"But if you ruffle up the surface of the sea, the light gets scattered in a lot of directions, and the reflection would be much dimmer. We did the same thing with radar on Titan."

The radar measurements suggest the surface of Ligeia Mare is eerily still. "Cassini's radar sensitivity in this experiment is one millimeter, so that means if there are waves on Ligeia Mare, they're smaller than one millimeter. That's really, really smooth," Zebker said.

One possible explanation for the sea's calmness is that no winds happened to be blowing across that region of the moon when Cassini made its flyby.

Another possibility is that a thin layer of some material is suppressing wave action. "For example, on Earth, if you put oil on top of a sea, you suppress a lot of small waves," Zebker said.

Cassini also measured microwave radiation emitted by the materials that make up Titan's surface.

By analyzing those measurements, and accounting for factors such as temperature and pressure, Zebker's team confirmed previous findings that the terrain around Ligeia Mare is composed of solid organic material, likely the same methane and ethane that make up the sea.

"Like water on Earth, methane on Titan can exists as a solid, a liquid, and a gas all at once," Zebker said.

Titan's similarities to Earth make it a good model for our own planet's early evolution, Zebker said. "Titan is different in the details from Earth, but because there is global circulation happening, the big picture is the same," he added.

"Seeing something in two very different environments could help reveal the overall guiding principles for the evolution of planetary bodies, and help explain why Earth developed life and Titan didn't."

More Information: "Surface of Ligeia Mare, Titan, from Cassini altimeter and radiometer analysis" H.Zebler et al.: 30 JAN 2014 - DOI: 10.1002/2013GL058877

NASA Cassini nears 100th Titan flyby with a look back

This artist’s concept shows a possible model of Titan’s internal structure that incorporates data from NASA’s Cassini spacecraft. 

In this model, Titan is fully differentiated, which means the denser core of the moon has separated from its outer parts. 

This model proposes a core consisting entirely of water-bearing rocks and a subsurface ocean of liquid water. 

The mantle, in this image, is made of icy layers, one that is a layer of high-pressure ice closer to the core and an outer ice shell on top of the sub-surface ocean. 

Credit: A. D. Fortes/UCL/STFC

Ten years ago, we knew Titan as a fuzzy orange ball about the size of Mercury. We knew it had a nitrogen atmosphere—the only known world with a thick nitrogen atmosphere besides Earth but what might lie beneath the hazy air was still just a guess.

On March 6, NASA’s Cassini spacecraft will swoop down within 933 miles (1,500 kilometers) of Titan to conduct its 100th flyby of the Saturn moon.

Each flyby gives us a little more knowledge of Titan and its striking similarities to our world.

Even with its cold surface temperatures of minus 290 degrees Fahrenheit (94 kelvins), Titan is like early Earth in a deep freeze.

Since its 2004 arrival at Saturn, Cassini's radar instrument has identified remarkable surface features on Titan.

The features include lakes and seas made of liquid methane and ethane, which are larger than North America's Great Lakes, and an extensive layer of liquid water deep beneath the surface.

Organic molecules abound in Titan's atmosphere, formed from the breakup of methane by solar radiation.

Michael Malaska

A recent innovation was the discovery that radar could be used to determine the depth of a Titan sea.

"It's something we didn't think we could do before," said Michael Malaska, an affiliate of the Cassini radar team at NASA's Jet Propulsion Laboratory, Pasadena, Calif.

"The radar can measure the depth by receiving two different bounces: one from the surface and one from the bottom of the sea."

"This technique was used to determine that Ligeia Mare, the second largest sea on Titan, is about 160 meters [525 feet] deep."

"When coupled with some laboratory experiments, it gives us information about the composition of the liquid in Ligeia Mare, too."

As spring turns to summer in Titan's northern hemisphere for the first time since Cassini arrived at Saturn, scientists are looking forward to entering potentially the most exciting time for Titan weather - with waves and winds picking up.

With increasing sunlight, the north polar lakes and seas can now be seen in near-infrared images, enabling scientists to learn more about their composition and giving them clues about the surrounding terrain.

Jonathan Lunine

"Methane is not only in the atmosphere, but probably in the crust," said Jonathan Lunine, a scientist on the Cassini mission at Cornell University, Ithaca, N.Y.

"It's a hint there are organics not only in Titan's air and on the surface, but even in the deep interior, where liquid water exists as well."

"Organics are the building blocks of life, and if they are in contact with liquid water, there could be a chance of finding some form of life."

Linda Spilker

Linda Spilker, Cassini project scientist at JPL, speculated on the type of life that could exist.

"The astrobiological potential for Titan is two-fold," she said. "Could a unique form of methane-based life exist in Titan's liquid lakes and seas? With a global ocean of liquid water beneath its icy crust, could life exist in Titan's subsurface ocean?"

Although the official Cassini mission name for this flyby is T-99, it is, in fact, the 100th targeted Titan flyby of the mission.

Why the discrepancy? An extra flyby was inserted early in the mission, after the Titan flybys had been named.

NASA's Cassini Image: Titan's Ligeia Mare - Second largest liquid lake

Ligeia Mare represents the second largest known body of liquid on Saturn's moon, Titan, shown here in a false-colour image obtained by NASA's Cassini mission. 

Ligeia Mare contains liquid hydrocarbons, such as ethane and methane, and makes up one of the many seas and lakes located in Titan's north polar region. 

The image consists of a false-colour mosaic of synthetic aperture radar images obtained by the Cassini spacecraft between February 2006 and April 2007. 

In this image, liquids, dark to the radar, appear black and the solid surface of Titan, which appears bright to the radar, appears yellow. 

Image released May 22, 2013.