An illustration of a Titanic lake by Ron Miller. All rights reserved. Used with permission.
Titan — that moon of Saturn that has what some scientists consider precursors to elements for life — is a neat place to study because it also has a liquid cycle. But how the hydrocarbons move from the moon’s hundreds of lakes and seas into the atmosphere and the crust is still being examined.
A new study suggests that rainfall on Titan changes when it interacts with underground icy clathrates, which are watery structures that can include methane or ethane. This can make it easier for reservoirs to be created.
“We knew that a significant fraction of the lakes on Titan’s surface might possibly be connected with hidden bodies of liquid beneath Titan’s crust, but we just didn’t know how they would interact,” stated lead author Olivier Mousis, a Cassini research associate at the University of Franche-Comté in France. “Now, we have a better idea of what these hidden lakes or oceans could be like.”
Artist’s conception of a possible structure for underground liquid reservoirs on Saturn moon’s Titan. From top, the layers include a porous icy crust, alkanofer in porous icy crust, expanding clathrate layer in porous icy crust and a non-porous icy crust. Credit: ESA/ATG medialab
This information is based on models of how the reservoirs would move through the crust of the icy moon. Clathrates would form at the bottom of reservoirs (which are filled with methane) and gradually split its molecules into solid and liquid components. Over time, this would transform the methane into propane or ethane.
“Importantly, the chemical transformations taking place underground would affect Titan’s surface,” the Jet Propulsion Laboratory stated.
“Lakes and rivers fed by springs from propane or ethane subsurface reservoirs would show the same kind of composition, whereas those fed by rainfall would be different and contain a significant fraction of methane. This means researchers could examine the composition of Titan’s surface lakes to learn something about what is happening deep underground.”
More about the research is available in the print version of the Sept. 1 edition of Icarus. Of note, the Cassini spacecraft is going to do another flyby of Titan in 17 days — its 105th, according to the spacecraft website.
Sunlight and shadow combine in this photo of Saturn and its rings taken Aug. 19, 2014. Credit: NASA/JPL/Space Science Institute
When Saturn is at its closest to Earth, it’s three-quarters of a billion miles away — or more than a billion kilometers! That makes these raw images from the ringed planet all the more remarkable.
Nearly every day, the Cassini spacecraft beams back what it sees at Saturn and the images are put up on this NASA website. This week, for example, it was checking out Saturn’s rings. We have a few of the pictures below, plus an older picture of the entire planet for reference.
Saturn’s rings are believed to be about 4.4 billion years old — that’s close to the age of the Solar System itself. Astronomers, however, have only known about them since the 1600s, when Galileo Galilei was trying to make sense of some funny-looking shapes on either side of the planet in his telescope.
According to NASA, the particles in the rings range from dust-sized to mountain-sized. Some of Saturn’s dozens of moons act as shepherds to the rings, keeping gaps open. You can read more about what we know about their origins here.
The Cassini spacecraft looks to the side of Saturn’s rings in this picture from Aug. 19, 2014. Credit: NASA/JPL/Space Science InstituteBands prominently feature in this raw picture of Saturn taken by the Cassini spacecraft Aug. 17, 2014. Credit: NASA/JPL/Space Science InstituteDifferent shades shine in this raw image of Saturn’s rings taken by the Cassini spacecraft taken Aug. 19, 2014. Credit: NASA/JPL/Space Science InstituteSaturn and its rings, as seen from above the planet by the Cassini spacecraft. Credit: NASA/JPL/Space Science Institute. Assembled by Gordan Ugarkovic.
The shadow of the Opportunity rover lies on the Martian surface in this picture taken on Sol 3752, on Aug. 13. The rover is on the west rim of Endeavour Crater, near the Martian equator. Its landing site was Meridani Planum. Credit: NASA/JPL-Caltech/Cornell/Arizona State Univ.
Many of us in the northern hemisphere are on summer vacation right now, and others are dreaming of it. While taking off somewhere exotic requires time and money, looking at pictures around the solar system provides cheaper thrills — in stranger places!
Several spacecraft roaming our planetary neighborhood regularly send back raw images of what they’re seeing. Here are some views from them taken in the past week.
Mars: After setting an off-word driving record, the Opportunity rover is still trundling on Mars after more than 10 years of operations. One of its latest raw images, above, shows its shadow and tracks on the surface of the Red Planet. Its heading to a destination called “Marathon Valley”, which is a likely spot for clay materials, and recently observed a transit of the moon Phobos. The rover’s computer had a brief reset, but is in good health besides that.
Tracks of the Curiosity rover crisscross Mars in this picture taken on Sol 719 (Aug. 14, 2014). Credit: NASA/JPL-Caltech
Mars: The Curiosity rover — which recently celebrated its two-year Earth birthday on Mars — has been on the move itself. Scientists are carefully moving the rover to its next science destination, about 1/3 of a mile (500 meters) away. The challenge is the extremely rocky terrain is damaging the rover’s wheels, but NASA said a recent drive through a rocky stretch produced less wear than feared.
A lava surface in southern Elysium Planitia taken by the Mars Reconnaissance Orbiter’s High Resolution Imaging Science Experiment (HiRISE). Credit: NASA/JPL/University of Arizona
Mars: These strange features spotted by the Mars Reconnaissance Orbiter are puzzling scientists. Usually the cones you see are indicative of lava features, but these are smaller than usual. “What’s really odd here is that the cones are associated with lighter areas with polygonal patterns,” stated the University of Arizona on its blog for the High Resolution Imaging Science Experiment (HiRISE). “Such polygons are commonly visible on the denser portions of lava flows, while the rougher areas have more broken-up low-density crust.”
A raw image of the Sun taken by the Solar and Heliospheric Observatory (SOHO) on Aug. 15, 2014. Credit: ESA/NASA/SOHO
Sun: The Solar and Heliospheric Observatory (SOHO) is one of a few sentinels keeping watch over the Sun for sunspots and other signs of solar activity. This allows scientists to make better predictions about when solar storms sweep over our planet, which is important for protecting satellites and infrastructure from the worst of these storms.
A raw image of Saturn taken by the Cassini spacecraft. Credit: NASA/JPL/Space Science Institute
Saturn: The Cassini spacecraft has been busily gazing at Saturn and its moons in the past week, including looking at temperatures in the atmosphere (specifically, in the upper troposphere and tropopause) in the gas giant. Just visible in this image is a huge hexagonal storm that scientists previously said acts somewhat like the Earth’s ozone hole.
A raw view of Titan taken by the Cassini spacecraft Aug. 13, 2014. Credit: NASA/JPL/Space Science Institute
Titan: Saturn’s largest moon — which contains organic compounds that could be precursors to life’s chemistry — is undergoing some changes as summer approaches. A few days ago, scientists noted that clouds are starting to form in Titan’s northern hemisphere. While they’re not sure yet if it will herald summer, scientists added that the lack of clouds before that defied models.
A close-up view of Comet 67P/Churyumov–Gerasimenko taken by the Rosetta spacecraft on Aug. 7, 2014. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
Comet 67P/Churyumov–Gerasimenko: The Rosetta spacecraft just arrived at this comet on Aug. 6, and has been sending back a few images of this small body that is speeding towards the Sun. You may recognize this particular image as part of the basis for a 3-D image that was released yesterday. Meanwhile, team members are examining dust production of the comet, which has already started as it heads to its closest Sun approach (between Earth and Mars) in about a year.
Clouds swirl near Titan's north pole in this annotated still image from the Cassini mission. Credit: NASA/JPL-Caltech/Space Science Institute
Swoosh! At long last, and later than models predicted, clouds are starting to appear on Titan’s nothern hemisphere. The region is just starting to enter a seven-year-long summer, and scientists say this could be an indication of coming summer storms there.
This moon of Saturn is of particular interest to astrobiologists because it has hydrocarbons (like ethane and methane), which are organic molecules that are possible precursors to the chemistry that made life possible. But what is also neat about Titan is it has its own weather system and liquid cycle — which makes it closer to Earth than to our own, nearly atmosphere-less Moon.
“The lack of northern cloud activity up til now has surprised those studying Titan’s atmospheric circulation,” wrote Carolyn Porco, the imaging lead for Cassini, in a message distributed to journalists.
“Today’s reports of clouds, seen a few weeks ago, and other recent indicators of seasonal change, are exciting for what they imply about Titan’s meteorology and the cycling of organic compounds between northern and southern hemispheres on this unusual moon, the only one in our solar system covered in liquid organics.”
Clouds swirl near Titan’s north pole in this annotated still image from the Cassini mission. Credit: NASA/JPL-Caltech/Space Science Institute
The pictures were taken by the Cassini spacecraft, which has been orbiting Saturn and its moons since 2004. The satellite arrived at the system in time to see clouds forming in the southern hemisphere, but the moon has been nearly bereft of clouds since a large storm occurred in 2010.
This particular cloud system occurred over Ligeia Mare, which is near Titan’s north pole, and included gentle wind speeds of about seven to 10 miles per hour (11 to 16 kilometers per hour.)
The sequence takes place between July 20 and 22, with most of the pictures separated by about 1-2 hours (although there is a 17.5-hour jump between frames 2 and 3.)
Wow! Check out this video of the Moon passing in front of Saturn from a viewpoint in Brisbane, Australia. This type of phenomenon, called an occultation, happens when one celestial body passes in front of the other from an observer’s standpoint. You can see some information about a June 10 occultation of Saturn, for example, at this link.
“There has been a fair amount of post-processing done on the images to get to this result. The first stage was to adjust the source images so that detail was visible both on Saturn and on the Moon. This is because the two objects are quite different in brightness, and so each individual exposure results in a slightly over-exposed Moon and a slightly under-exposed Saturn,” wrote Teale Britstra, who created the video, on Vimeo.
“After initial processing, the series of images were imported into video editing software, and the resulting footage stabilized to eliminate some small tracking errors between shots,” Britstra continued.
“There was also one LARGE tracking error, where I had to physically move the telescope. This was because the Moon was sinking towards the western horizon and some nearby, large trees which would have obscured the shot had the scope not been moved. This can be seen in the resulting footage as the period where the Moon appears to slow down and slightly change direction.”
This dramatic view looks across the region of Enceladus' geyser basin and down on the ends of the Baghdad and Damascus fractures that face Saturn. The image, which looks approximately in the direction of Saturn, was taken from a more elevated viewpoint than other Cassini survey images of this area of the moon's south pole. Credit: NASA/JPL-Caltech/SSI
Scientists analyzing the reams of data from NASA’s Cassini orbiter at Saturn have discovered 101 geysers erupting from the intriguing icy moon Enceladus and that the spewing material of liquid water likely originates from an underground sea located beneath the tiny moons ice shell, according to newly published research.
The geysers are composed of tiny icy particles, water vapor and trace amounts of simple organic molecules. They were first sighted in Cassini imagery snapped during flyby’s of the 310-mile-wide (500 kilometers wide) moon back in 2005 and immediately thrust Enceladus forward as a potential abode for alien life beyond Earth and prime scientific inquisition.
Liquid water, organic molecules and an energy source are the key requirements for life as we know it.
The eruptions emanated from a previously unknown network of four prominent “tiger stripe” fractures, named Damascus, Baghdad, Cairo and Alexandria sulci, located at the south polar region of Saturn’s sixth largest moon.
Using imagery gathered over nearly seven years of surveys by Cassini’s cameras, researchers generated a survey map of the 101 geysers erupting from the four tiger strips.
This artist’s rendering shows a cross-section of the ice shell immediately beneath one of Enceladus’ geyser-active fractures, illustrating the physical and thermal structure and the processes ongoing below and at the surface. Image Credit: NASA/JPL-Caltech/Space Science Institute
The new findings and theories on the physical nature of how the geysers erupt have been published in two articles in the current online edition of the Astronomical Journal.
Scientists had initially postulated that the origin of the geysers could be frictional heating generated from back and forth rubbing of the opposing walls of the tiger stripe fractures that converted water ice into liquids and vapors. Another theory held that the opening and closing of the fractures allowed water vapor from below to reach the surface.
The geysers locations was eventually determined to coincide with small local hot spots erupting from one of the tiger stripe fractures after researchers compared low resolution thermal emission maps with the geysers’ locations and found the greatest activity at the warmest spots.
After later high-resolution data was collected in 2010 by Cassini’s heat-sensing instruments the geysers were found to coincide with small-scale hot spots, measuring only a few dozen feet (or tens of meters) across.
“Once we had these results in hand we knew right away heat was not causing the geysers, but vice versa,” said Carolyn Porco, leader of the Cassini imaging team from the Space Science Institute in Boulder, Colorado, and lead author of the first paper. “It also told us the geysers are not a near-surface phenomenon, but have much deeper roots.”
This graphic shows a 3-D model of 98 geysers whose source locations and tilts were found in a Cassini imaging survey of Enceladus’ south polar terrain by the method of triangulation. While some jets are strongly tilted, it is clear the jets on average lie in four distinct “planes” that are normal to the surface at their source location. Image credit: NASA/JPL-Caltech/Space Science Institute
“Thanks to recent analysis of Cassini gravity data, the researchers concluded the only plausible source of the material forming the geysers is the sea now known to exist beneath the ice shell. They also found that narrow pathways through the ice shell can remain open from the sea all the way to the surface, if filled with liquid water,” according to a NASA press release.
These are very exciting results in the search for life beyond Earth and clearly warrant a follow up mission.
“In casting your sights on the geysering glory of Enceladus, you are looking at frozen mist that originates deep within the solar system’s most accessible habitable zone,” writes Porco in her Captain’s Log summary of the new findings.
Surveyor’s Map of Enceladus’ Geyser Basin – On this polar stereographic map of Enceladus’ south polar terrain, all 101 geysers have been plotted whose source locations have been determined in Cassini’s imaging survey of the moon’s geyser basin. Credit: NASA/JPL-Caltech/SSI
The Cassini-Huygens mission is a cooperative project between NASA, the European Space Agency (ESA) and the Italian Space Agency (ASI). Cassini was launched by a Titan IV rocket in 1997 and arrived at Saturn in 2004.
In 2005 Cassini deployed the Huygens probe which landed on Titan, Saturn’s largest moon sporting oceans of organic molecules and another prime location in the search for life.
The Cassini mission will conclude in 2017 with an intentional suicide dive into Saturn to prevent contamination on Titan and Enceladus – but lots more breathtaking science will be accomplished in the meantime!
Stay tuned here for Ken’s Earth & Planetary science and human spaceflight news.
A hexagonal storm on Saturn rages in this image taken July 2, 2014. Credit: NASA/JPL/Space Science Institute
We space people are very lucky to get glimpses of Saturn (and other planets!) regularly through the raw images feature on a few spacecraft websites. This allows anyone to get a hold of the pictures as they come back from afar, allowing you to view them or alter them to try and see what they’re all about.
In an era where we are so used to high-definition pictures, examining these blurry, black-and-white shots feels novel. It makes the spacecraft seem like it is action somehow: catching a glimpse of a ringed planet as it swings by, for example.
Part of Saturn’s rings are visible in this July 2, 2014 image from the Cassini spacecraft. Credit: NASA/JPL/Space Science InstituteGazing at Saturn’s rings. Picture taken by the Cassini spacecraft June 30, 2014. Credit: NASA/JPL/Space Science InstituteA dark shadow falls across Saturn and its rings in this raw image taken by the Cassini spacecraft July 2, 2014. Credit: NASA/JPL/Space Science InstituteEerie shadows play across Saturn in this Cassini image taken in June 2014. Credit: NASA/JPL/Space Science Institute
Saturn's northern storm marches through the planet's atmosphere in the top right of this false-color mosaic from NASA's Cassini spacecraft. Credit: NASA/JPL-Caltech/Space Science Institute
We’re spoiled, don’t you know? It was 10 years ago today that the Cassini spacecraft entered Saturn’s system, and it has been busily beaming back pictures of the ringed planet and its (many) moons ever since. We’ve learned more about seasons on Titan, investigated plumes on Enceladus, and examined phenomena such as auroras on Saturn.
Embedded in this story are 20 of our favourite pictures from Universe Today’s archive of Cassini discoveries, which you can check out below the jump.
It’s only a fraction of the more than 332,000 images received from the spacecraft, which is in excellent health and has seen its mission extended three times past its original 2008 expiry date. Additionally, more than 3,000 scientific papers have been generated. More cool stats in this NASA infographic.
The full mosaic from the Cassini imaging team of Saturn on July 19, 2013… the “Day the Earth Smiled”In this unique mosaic image combining high-resolution data from the imaging science subsystem and composite infrared spectrometer aboard NASA’s Cassini spacecraft, pockets of heat appear along one of the mysterious fractures in the south polar region of Saturn’s moon Enceladus. Image credit: NASA/JPL/GSFC/SWRI/SSISaturn, imaged by Cassini on approach. Credit: CICLOPSTitan and Dione as seen by Cassini. Credit: NASA/JPL/Space Science InstituteThis image taken by the Cassini orbiter on Oct. 15, 2007, shows Saturn’s A and F rings, the small moon Epimetheus and smog-enshrouded Titan, the planet’s largest moon. The image is colorized to approximate the scene as it might appear to human eyes. (Credit: NASA/JPL/Space Science Institute)Cassini imaging scientists used views like this one to help them identify the source locations for individual jets spurting ice particles, water vapor and trace organic compounds from the surface of Saturn’s moon Enceladus. Credit: NASARaw image from Cassini on May 18. Credit: NASA/JPL/SSIHemispheric color differences on Saturn’s moon Rhea are apparent in this false-color view from NASA’s Cassini spacecraft. This image shows the side of the moon that always faces the planet. Image Credit: NASA/JPL/SSIThree of Saturn’s moons bunch together in this image by Cassini. Credit: NASA/JPL/Space Science Institute. Click for larger image.This mosaic of Titan was created from the first flyby of the moon by Cassini in 2004. Credit: NASA/JPL/SSPhoebe imaged by the Cassini spacecraft. Image Credit: NASACassini VIMS image of specular reflections in one of Titan’s lakes from a flyby on July 24, 2012 (NASA/JPL-Caltech/SSI/Jason W. Barnes et al.)A crescent Dione was seen by Cassini on January 29, 2011 from approximately 767,922 kilometers away. Credit: NASA/JPL/SSIRhea, as seen by Cassini. Credit: NASACassini captured this startling image of Saturn’s moon Hyperion. Photo Credit: NASA/JPLets of water ice particles spew from Saturn’s moon Enceladus in this image obtained by NASA’s Cassini spacecraft on Aug. 13, 2010. Image credit: NASA/JPL/SSIThis false-color composite image shows Saturn’s rings and southern hemisphere. The composite image was made from 65 individual observations by Cassini’s visual and infrared mapping spectrometer in the near-infrared portion of the light spectrum on Nov. 1, 2008. Credit: NASA/JPL/University of ArizonaThis mosaic of images from NASA’s Cassini spacecraft shows three fan-like structures in Saturn’s tenuous F ring. Such “fans” suggest the existence of additional objects in the F ring. Image credit: NASA/JPL/SSICassini came within 25 kilometers (15.6 miles) of the surface of Enceladus on Oct. 5, 2008. Image credit: NASA/JPL/Space Science Institute
According to a study from UCLA, Titan experiences severe methane rainstorms, leading to a the alluvial fans found found in both hemispheres. Credit:
NASA/JPL-Caltech/Space Science Institute
It’s well accepted that moons form after planets. In fact, only a few months ago, astronomers spotted a new moon forming deep within Saturn’s rings, 4.5 billion years after the planet initially formed.
But new research suggests Saturn’s icy moon Titan — famous for its rivers and lakes of liquid methane — may have formed before its parent planet, contradicting the theory that Titan formed within the warm disk surrounding an infant Saturn.
A combined NASA and ESA-funded study has found firm evidence that the nitrogen in Titan’s atmosphere originated in conditions similar to the cold birthplace of the most ancient comets from the Oort cloud — a spherical shell of icy particles that enshrouds the Solar System.
The hint comes in the form of a ratio. All elements have a certain number of known isotopes — variants of that element with the same number of protons that differ in their number of neutrons. The ratio of one isotope to another isotope is a crucial diagnostic tool.
In planetary atmospheres and surface materials, the amount of one isotope relative to another isotope is closely tied to the conditions under which materials form. Any change in the ratio will allow scientists to deduce an age for that material.
Kathleen Mandt from the Southwest Research Institute in San Antonio and colleagues analyzed the ratio of nitrogen-14 (seven protons and seven neutrons) to nitrogen-15 (seven protons and eight neutrons) in Titan’s atmosphere.
“When we looked closely at how this ratio could evolve with time, we found that it was impossible for it to change significantly,” Mandt said in a press release. “Titan’s atmosphere contains so much nitrogen that no process can significantly modify this tracer even given more than four billion years of Solar System history.”
The team found that our Solar System is not old enough for this nitrogen isotope ratio to have changed as much as it has. By comparing the small change within this ratio, Mandt and colleagues found that it seemed more similar to Oort cloud comets than to Solar System bodies including planets and comets born in the Kuiper belt. The team is eager to see whether their findings are supported by data from ESA’s Rosetta mission, which will study comet 67P/Churyumov-Gerasimenko later this year.
Finally, the study also has implications for Earth. In the past, researchers assumed a connection between comets, Titan and Earth. But these results show that the nitrogen isotope ratio is different on Titan and Earth, suggesting the sources of Earth’s and Titan’s nitrogen must have been different.
It’s unclear whether Earth received nitrogen from early meteorites or if it was captured directly from the disk of gas that formed the Solar System.
“This exciting result is a key example of Cassini science informing our knowledge of the history of [the] Solar System and how Earth formed,” said Scott Edgington, Cassini deputy project scientist at NASA’s Jet Propulsion Laboratory.
The research was published this week in the Astrophysical Journal Letters.
Saturn's moon Atlas peeks out between the rings in this Cassini shot taken Jan. 23, 2014. Credit: NASA/JPL-Caltech/Space Science Institute
See that small pixel? That’s an entire moon you’re looking at! Peeking between the rings of Saturn is the tiny saucer-shaped moon Atlas, as viewed from the Cassini spacecraft. The image is pretty, but there’s also a scientific reason to watch the planet’s many moons while moving around the rings.
“Although the sunlight at Saturn’s distance is feeble compared to that at the Earth, objects cut off from the Sun within Saturn’s shadow cool off considerably,” NASA stated.
“Scientists study how the moons around Saturn cool and warm as they enter and leave Saturn’s shadow to better understand the physical properties of Saturn’s moons.”
And if you look at Atlas close-up, it looks a little like a flying saucer! The moon is only 20 miles (32 km) across, which is a bit shy of the length of a marathon. The Voyager 1 team spotted the moon in 1980 when the spacecraft zoomed through the system. You can learn more about Saturn’s moons here.
Cassini is still in excellent health (it arrived at Saturn in 2004, and has been in space since 1997), and scientists are eagerly getting ready for when Saturn gets to its summer solstice in 2017. Among the things being looked at is a hurricane at Saturn’s north pole.
Saturn’s moon Atlas. Left image: viewed from the side, at a scale of 0.6 miles (1 km) per pixel. Right image: the mid-southern latitudes, at 820 feet (250 m) per pixel. The images are composite views from the Cassini spacecraft. Credit: NASA/JPL/SSI
