Titan imaged by the Cassini spacecraft. Credit: NASA/JPL-Caltech/Space Science Institute
Sunlight can do fun things in space. For example: this recent picture of Titan (a moon of Saturn) shows sunlight hitting the moon’s surface as well as a southern vortex, just visible in the shadows of the picture.
“The sunlit edge of Titan’s south polar vortex stands out distinctly against the darkness of the moon’s unilluminated hazy atmosphere,” NASA stated. “The Cassini spacecraft images of the vortex led scientists to conclude that its clouds form at a much higher altitude — where sunlight can still reach — than the surrounding haze.”
Titan has intrigued scientists for decades, since the Voyager spacecraft first revealed it as a world socked in by orange haze. Cassini dropped off a lander on the surface, called Huygens, which took pictures on the surface in 2005. Besides that, the orbiter has revealed a lot about lakes, rain and other features of the moon in the year since.
Cassini has been orbiting the moon since 2004 and is still busily producing science, but there are concerns that NASA’s budget situation could cause the agency to shut down operations on the still-healthy spacecraft. There are no other missions to Saturn or Titan booked yet, although scientists do have intriguing ideas for exploration.
Saturn's moons (from left to right) Janus, Pandora, Enceladus, Mimas and Rhea. Rhea is on top of Saturn. Credit: NASA/JPL-Caltech/Space Science Institute
This picture is from a couple of years ago, but still worth the extra look. The Cassini spacecraft — busily circling Saturn and gathering data on the ringed planet and its moons — managed to grab five of Saturn’s 62 known moons in one shot. The European Space Agency highlighted the picture on its home page this week.
From left to right, you can see Janus, Pandora, Enceladus, Mimas and Rhea. Don’t be fooled by the rings near Rhea; those are actually Saturn’s rings. Rhea is just blocking the view of the planet from Saturn’s perspective during this picture portrait, which was taken on July 29, 2011.
The cornucopia of moons around Saturn is part of what makes that particular planet so interesting. Titan, the largest, is perhaps the most well-known because of its strange orange haze that intrigued astronomers when the twin Voyager spacecraft zoomed through the system in the 1980s. Cassini arrived in 2004 and revealed many more moons to science for the first time.
Color-composite of Titan made from raw Cassini images acquired on April 13, 2013 (added 4/17) NASA/JPL/SSI. Composite by J. Major.
“The dozens of icy moons orbiting Saturn vary drastically in shape, size, surface age and origin. Some of these worlds have hard, rough surfaces, while others are porous bodies coated in a fine blanket of icy particles. All have greater or smaller numbers of craters, and many have ridges and valleys,” NASA wrote on a web page about Saturn’s moons.
“Some, like Dione and Tethys, show evidence of tectonic activity, where forces from within ripped apart their surfaces. Many, like Rhea and Tethys, appear to have formed billions of years ago, while others, like Janus and Epimetheus, could have originally been part of larger bodies that broke up. The study and comparison of these moons tells us a great deal about the history of the Saturn System and of the solar system at large.”
Titan's north pole is home to many methane lakes. Credit: NASA
A combination of exceptionally clear weather, the steady approach of northern summer, and a poleward orbital path has given Cassini — and Cassini scientists — unprecedented views of countless lakes scattered across Titan’s north polar region. In the near-infrared mosaic above they can be seen as dark splotches and speckles scattered around the moon’s north pole. Previously observed mainly via radar, these are the best visual and infrared wavelength images ever obtained of Titan’s northern “land o’ lakes!”
Titan is currently the only other world besides Earth known to have stable bodies of liquid on its surface, but unlike Earth, Titan’s lakes aren’t filled with water — instead they’re full of liquid methane and ethane, organic compounds which are gases on Earth but liquids in Titan’s incredibly chilly -290º F (-180º C) environment.
While one large lake and a few smaller ones have been previously identified at Titan’s south pole, curiously almost all of Titan’s lakes appear near the moon’s north pole.
Infrared observations of Titan’s northern lakes. The cross marks Titan’s geographic north pole. (NASA/JPL-Caltech/SSI)
For an idea of scale, the large lake at the upper right above (and the largest lake on Titan) Kraken Mare is comparative in size to the Caspian Sea and Lake Superior combined. Kraken Mare is so large that sunlight was seen reflecting off its surface in 2009. Punga Mare, nearest Titan’s pole, is 240 miles (386 km) across.
Besides revealing the (uncannily) smooth surfaces of lakes — which appear dark in near-infrared wavelengths but would also be darker than the surrounding landscape in visible light — these Cassini images also show an unusually bright terrain surrounding them. Since the majority of Titan’s lakes are found within this bright region it’s thought that there could be a geologic correlation; is this Titan’s version of karst terrain, like what’s found in the southeastern U.S. and New Mexico? Could these lakes be merely the visible surfaces of a vast underground hydrocarbon aquifer? Or are they shallow pools filling depressions in an ancient lava flow?
Annotated infrared mosaic of Titan’s north pole (NASA/JPL-Caltech/SSI)
Or, are they the remains of once-larger lakes and seas which have since evaporated? The orange-hued regions in the false-color mosaic may be evaporite — the Titan equivalent of salt flats on Earth. The evaporated material is thought to be organic chemicals originally from Titan’s haze particles that were once dissolved in liquid methane.
“Is this an indication that with increased warmth, the seas and lakes are starting to evaporate, leaving behind a deposit of organic material,” wrote Carolyn Porco, Cassini Imaging Team Leader, in an email earlier today. “…in other words, the Titan equivalent of a salt-flat?”
The largest lake at Titan’s south pole, Ontario Lacus, has been previously compared to such an ephemeral lake in Namibia called the Etosha Pan. (Read more here.)
These observations are only possible because of the extended and long-term study of Saturn and its family of moons by the Cassini spacecraft, which began with its establishing orbit in 2004 and has since continued across multiple seasons over a third of the ringed planet’s year. The existence of methane lakes on Titan is undoubtedly fascinating, but how deep the lakes are, where they came from and how they behave in Titan’s environment have yet to be discovered. Luckily, the changing season is on our side.
“Titan’s northern lakes region is one of the most Earth-like and intriguing in the solar system,” said Linda Spilker, Cassini project scientist, based at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “We know lakes here change with the seasons, and Cassini’s long mission at Saturn gives us the opportunity to watch the seasons change at Titan, too. Now that the sun is shining in the north and we have these wonderful views, we can begin to compare the different data sets and tease out what Titan’s lakes are doing near the north pole.”
The images shown above were obtained by Cassini’s visual and infrared mapping spectrometer (VIMS) during a close flyby of Titan on Sept. 12, 2013.
Read more on the Cassini Imaging Central Laboratory for Operations (CICLOPS) site here and on the NASA site here.
“But how thrilling it is to still be uncovering new territory on this fascinating moon… a place that, until Cassini’s arrival at Saturn nearly 10 years ago, was the largest single expanse of unseen terrain we had remaining in our solar system. Our adventures here have been the very essence of exploration. And it’s not over yet!”
The Voyager spacecraft have been on an extensive mission of discovery that has lasted some 36 years. Image Credit: NASA/JPL
Yesterday, NASA announced that as of August 2012, Voyager 1 is in a new frontier to humanity: interstellar space. Our most distant spacecraft is now in a region where the plasma (really hot gas) environment comes more from between the stars than from the sun itself. (There’s still debate as to whether it’s in or out of the solar system, as this article explains.)
The plucky spacecraft is close to 12 billion miles (19 million kilometers) from home, and in its 36 years of voyaging has taught us a lot about the planets, their moons and other parts of space. Here are 10 of some of its most historic moments. Did we miss any? Let us know in the comments.
10. The launch: Aug. 20, 1977
Voyager 1 launches from the Kennedy Space Center on Sept. 5, 1977. Credit: NASA
Voyager 1 blasted off from Cape Canaveral on Sept. 5, 1977. Its twin, Voyager 2, departed Earth 16 days earlier. Each spacecraft carried various scientific instruments on board as well as a “Golden Record” that had sounds of Earth on it, as well as a diagram showing where Earth is in the universe.
9. Capturing the Earth and Moon together for the first time
On Sept. 18, 1977, Voyager 1 took three images of the Earth and Moon that were combined into this one image. The moon is artificially brightened to make it show up better. Credit: NASA
About two weeks after launching, Voyager 1 turned back towards Earth and took three images, which were combined into this single view of the Earth and Moon together in space. This was the first time both bodies were pictured together, NASA said.
8. The ‘Pale Blue Dot’ image
Voyager 1 pale blue dot. Image credit: NASA/JPL
On February 14, 1990, Voyager 1 was about 3.7 billion miles (6 billion kilometers) away from Earth. Scientists commanded the spacecraft to turn its face towards the solar system and snap some pictures of the planets. Among them was this famous image of Earth, which astronomer Carl Sagan called the Pale Blue Dot. “Look again at that dot. That’s here. That’s home. That’s us,” wrote Sagan in his 1997 book of the same name. In 2013, the spacecraft Cassini also took a picture of Earth, and NASA encouraged everyone to wave back.
7. Finding moons “shepherding” Saturn’s F ring
Prometheus, a small potato-shaped moon of Saturn, shown in this Voyager 1 picture interacting with the planet’s F ring. Credit: NASA/JPL/SSI
Voyager 1 spotted Prometheus and Pandora, two moons of Saturn that keep the F ring separate from the rest of the debris, as well as Atlas, which “shepherds” the A ring. More recently, astronomers have found even more interesting things in Saturn’s rings — such as rain.
6. Spotting what appeared to be a LOT of water ice on Saturn’s moons
Encaladus, a moon of Saturn, as shown in this Voyager 1 image. Credit: NASA
After many years of seeing Saturn’s moons as mere points of light, Voyager 1 buzzed several of them in its quick flyby through the system: Dione, Enceladus, Mimas, Rhea, Tethys and Titan among them. Many of these moons appeared to be icy, which was a surprising find since astronomers previously thought water was pretty rare in the Solar System. We know better now.
5. Imaging Titan’s orange haze
Saturn’s moon Titan lies under a thick blanket of orange haze in this Voyager 1 picture. Credit: NASA
Voyager 1 pictures such as this tortured astronomers for decades — what lies beneath this mysterious haze surrounding Titan, Saturn’s moon? That mystery, in fact, inspired the European Space Agency to send a lander to the moon, called Huygens, which successfully reached the surface in 2005.
4. Finding active volcanoes on Io
Io’s blotchy volcanoes are clearly visible in this image from Voyager 1. Credit: NASA
Voyager 1 helped show us that the Solar System is full of very interesting moons. At Io — a moon of Jupiter — it turns out the moon flexes during its 42-hour orbit of massive Jupiter, which powers a lot of volcanic activity.
3. Voyager 1 becomes the most distant human object
A 2013 computer-generated snapshot riding along with Voyager 1’s looking back at the Sun and inner solar system. The positions of Voyager 2 and Pioneers 10 and 11 show within the viewport as well.
On Feb. 17, 1998, Voyager 1’s distance surpassed that of another long-flying probe, Pioneer 10. This made Voyager 1 the farthest-flung human object in space.
2. Riding the “magnetic highway”
Artist concept of NASA’s Voyager 1 spacecraft exploring a new region in our solar system called the “magnetic highway.” Credit: NASA/JPL-Caltech
In December, NASA said Voyager 1 had reached an area (as of July 28, 2012) where high-energy magnetic particles were starting to bleed through the bubble of lower-energy particles from our sun. “Voyager’s discovered a new region of the heliosphere that we had not realized was there. It’s a magnetic highway where the magnetic field of the Sun is connected to the outside. So it’s like a highway, letting particles in and out,” said project scientist Ed Stone at the time. After that point, as more measurements were analyzed by different teams, there was a lot of debate as to whether Voyager had reached interstellar space.
1. Reaching interstellar space
This graphic shows the main evidence that Voyager 1 has reached interstellar space. The blue line shows particle density, which dropped as Voyager 1 moved away from the sun, and then jumped again after it crossed the “termination shock” that is where the sun’s solar wind (particles streaming from the sun) slows down. Credit: NASA/JPL-Caltech
With Voyager 1 now known to be in interstellar space, we’re lucky enough to have a few years left to communicate with it before it runs out of power. All of the instruments will be turned off by 2025, and then engineering data will be available for about 10 years beyond that. The silent emissary from humanity will then come within 1.7 light years of an obscure star in the constellation Ursa Minor (the Little Bear) called AC+79 3888 in the year 40,272 AD and then orbit the center of the Milky Way for millions of years.
UV image of Titan acquired by Cassini on April 13 (NASA/JPL-Caltech/SSI)
As high summer slowly but steadily approaches on Saturn, Cassini is opening a window to the seasonal changes that occur not only on the ringed planet but also its moons. Here we can see a dark band developing around Titan’s north polar latitudes, a “fancy collar” made visible in ultraviolet wavelengths.
Polar collars have previously been seen by both Hubble and Voyager 2, and in fact a southern version was observed by HST 5 years after the planet’s 1995 equinox.
This summer collar is thought to be part of a seasonal process, related to the migration of upper-level haze material within Titan’s atmosphere.
Source: CICLOPS (Cassini Imaging Central Laboratory for OPerationS)
A dense network of small rivers or swampy areas appears to connect some of the seas on Saturn's moon Titan, as seen in this comparison of data of the same area from two instruments on NASA's Cassini spacecraft. Images from the radar instrument are on the left and images from the visual and infrared mapping spectrometer (VIMS) are on the right. Credit: NASA/JPL-Caltech/University of Arizona
Are there waves on Titan’s lakes and seas? Cassini scientists say that the best chance of answering this question is with the May 23 flyby of Titan, when the Cassini spacecraft will be just 970 km (603 miles) over Titan’s biggest ‘lake,’ the northern sea named Ligeia Mare.
Lakes, seas, and rivers were discovered on Titan by Cassini in 2005, and since then, scientists and space enthusiasts have been intrigued about the possibility of what could be found in these bodies of hydrocarbon liquid. Future potential missions such as paddleboats have even been proposed.
Lakes, seas and rivers of liquid hydrocarbons cover much of the Titan’s northern hemisphere. Additionally, these hydrocarbons may rain down on the surface. The questions is, are these frigid liquid bodies capable of producing wave action, or would they be a rigid type of frigid? With surface temperature at -178 degrees Celsius (-289 degrees Fahrenheit), Titan’s environment is too cold for life as we may know it, but its environment, rich in the building blocks of life, is of great interest to astrobiologists.
Additionally, new models of Titan’s atmosphere prediction that as the seasons change in Titan’s northern hemisphere, waves could ripple across the moon’s hydrocarbon seas, and possibly even hurricanes could begin to swirl over these areas, too. The model predicting waves tries to explain data from the moon obtained so far by Cassini.
“If you think being a weather forecaster on Earth is difficult, it can be even more challenging at Titan,” said Scott Edgington, Cassini’s deputy project scientist at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “We know there are weather processes similar to Earth’s at work on this strange world, but differences arise due to the presence of unfamiliar liquids like methane. We can’t wait for Cassini to tell us whether our forecasts are right as it continues its tour through Titan spring into the start of northern summer.”
For the flyby on May 23, the altimetry data that will be collected by the radar instrument could show whether the surface of that sea is thick like molasses or as thin as liquid water on Earth.
In addition, radar will look for changes in small northern lakes last observed in previous flybys, the T-16 and T-19 flybys.
This flyby is a carefully planned sibling of the following flyby; the combination of the data from T-91 and T-92 will provide stereo views of the same geography, which will tell us about the depth of the lake walls.
Artist depiction of Huygens landing on Titan. Credit: ESA
It was eight years ago on January 14, 2005 that the Huygens spacecraft descended through Titan’s murky atmosphere and touched down – if a bit precariously – by bouncing, sliding and wobbling across the surface of Saturn’s largest moon Titan. This was the first time a probe had touched down on an alien world in the outer Solar System.
But that surface wasn’t quite what we expected.
While earlier studies of data from Huygens determined the surface of Titan to be quite soft, scientists now think the surface consisted of a hard outer crust but is soft underneath, so that if an object put more pressure on the surface, it sank in significantly.
“It is like snow that has been frozen on top,” said Erich Karkoschka, a co-author of a paper published in October 2012. “If you walk carefully, you can walk as on a solid surface, but if you step on the snow a little too hard, you break in very deeply.”
The scientists think that Huygens landed in something similar to a flood plain on Earth, but that it was dry at the time. The analysis reveals that, on first contact with Titan’s surface, Huygens dug a hole 12 cm deep, before bouncing out onto a flat surface.
The probe, tilted by about 10 degrees in the direction of motion, then slid 30–40 cm across the surface.
A new animation. top of the event has been created using real data recorded by Huygen’s instruments, allowing us to witness this historical moment as if we had been there.
ESA explains:
The animation takes into account Titan’s atmospheric conditions, including the Sun and wind direction, the behaviour of the parachute (with some artistic interpretation only on the movement of the ropes after touchdown), and the dynamics of the landing itself.
Even the stones immediately facing Huygens were rendered to match the photograph of the landing site returned from the probe, which is revealed at the end of the animation.
Split into four sequences, the animation first shows a wide-angle view of the descent and landing followed by two close-ups of the touchdown from different angles, and finally a simulated view from Huygens itself – the true Huygens experience.
Also, a ‘fluffy’ dust-like material – most likely organic aerosols that are known to drizzle out of the Titan atmosphere – was thrown up and suspended for around four seconds around the probe following the impact. The dust was easily lifted, suggesting it was most likely dry and that there had not been any ‘rain’ of liquid ethane or methane for some time prior to the landing.
Huygens was released from the Cassini spacecraft on Christmas Day 2004, and arrived at Titan three weeks later. The probe began transmitting data to Cassini four minutes into its descent and continued to transmit data after landing at least as long as Cassini was above Titan’s horizon, for about 90 minutes, and radio telescopes on Earth continued to receive Huygen’s signal well past the expected lifetime of the craft.
Cassini was supposed to receive Huygen’s signal over two channels, but because of an operational commanding error, only one channel was used. This means that only 350 pictures were received instead of 700 that were expected. All Doppler radio measurements between Cassini and Huygens were lost as well; however, Doppler radio measurements of Huygens from Earth were made, though not as accurate as the expected measurements that Cassini would have made. But when added to accelerometer sensors on Huygens and VLBI tracking of the position of the Huygens probe from Earth, reasonably accurate wind speed and direction measurements could still be derived.
Huygens is currently the most distant landing of any craft launched from Earth. Cassini has been in orbit around Saturn since July 2004, and will continue operations until 2017.
This artist's concept envisions what hydrocarbon ice forming on a liquid hydrocarbon sea of Saturn's moon Titan might look like. Image credit: NASA/JPL-Caltech/USGS
The Cassini spacecraft has been getting some strange data from Saturn’s moon Titan, and scientists will soon test out whether there might be “icebergs” of sorts, blocks of hydrocarbon ice floating on the surface of the lakes and seas of liquid hydrocarbon.
“One of the most intriguing questions about these lakes and seas is whether they might host an exotic form of life,” said Jonathan Lunine, a paper co-author and Cassini interdisciplinary Titan scientist at Cornell University, Ithaca, N.Y. “And the formation of floating hydrocarbon ice will provide an opportunity for interesting chemistry along the boundary between liquid and solid, a boundary that may have been important in the origin of terrestrial life.”
Titan is the only other body besides Earth in our solar system with stable bodies of liquid on its surface. But it is too cold on Titan for water to be liquid, so hydrocarbons like ethane and methane fill lakebeds and seas there, and scientists have determined there is even a likely cycle of precipitation and evaporation that involves hydrocarbons.
Ethane and methane are organic molecules, which scientists think can be building blocks for the more complex chemistry from which life arose.
Cassini has seen a vast network of these hydrocarbon seas cover Titan’s northern hemisphere, while a more sporadic set of lakes are in the southern hemisphere.
It has long been thought that lakes or seas dotted Titan, ever since Voyager 1 and 2 flew past the Saturn system in the early 1980’s. But with Titan’s thick atmosphere, direct evidence was not obtained until 1995 during observations from the Hubble Space Telescope. The Cassini mission has imaged and mapped many of these bodies of liquids on Titan.
The Cassini spacecraft has been getting mixed readings in the reflectivity of the surfaces of lakes on Titan. A smooth surface or liquids dotted with chunks of ice could be a possibility explanation for the readings.
Up to this point, Cassini scientists assumed that Titan lakes would not have floating ice, because solid methane is denser than liquid methane and would sink. But a new model considers the interaction between the lakes and the atmosphere, resulting in different mixtures of compositions, pockets of nitrogen gas, and changes in temperature. The result, scientists found, is that winter ice will float in Titan’s methane-and-ethane-rich lakes and seas if the temperature is below the freezing point of methane — minus 297 degrees Fahrenheit (90.4 kelvins). The scientists realized all the varieties of ice they considered would float if they were composed of at least 5 percent “air,” which is an average composition for young sea ice on Earth. (“Air” on Titan has significantly more nitrogen than Earth air and almost no oxygen.)
If the temperature drops by just a few degrees, the ice will sink because of the relative proportions of nitrogen gas in the liquid versus the solid. Temperatures close to the freezing point of methane could lead to both floating and sinking ice – that is, a hydrocarbon ice crust above the liquid and blocks of hydrocarbon ice on the bottom of the lake bed. Scientists haven’t entirely figured out what color the ice would be, though they suspect it would be colorless, as it is on Earth, perhaps tinted reddish-brown from Titan’s atmosphere.
“We now know it’s possible to get methane-and-ethane-rich ice freezing over on Titan in thin blocks that congeal together as it gets colder — similar to what we see with Arctic sea ice at the onset of winter,” said Jason Hofgartner, first author on the paper and a Natural Sciences and Engineering Research Council of Canada scholar at Cornell. “We’ll want to take these conditions into consideration if we ever decide to explore the Titan surface some day.”
Cassini’s radar instrument will be able to test this model by watching what happens to the reflectivity of the surface of these lakes and seas. A hydrocarbon lake warming in the early spring thaw, as the northern lakes of Titan have begun to do, may become more reflective as ice rises to the surface. This would provide a rougher surface quality that reflects more radio energy back to Cassini, making it look brighter. As the weather turns warmer and the ice melts, the lake surface will be pure liquid, and will appear to the Cassini radar to darken.
“Cassini’s extended stay in the Saturn system gives us an unprecedented opportunity to watch the effects of seasonal change at Titan,” said Linda Spilker, Cassini project scientist at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “We’ll have an opportunity to see if the theories are right.”
The HyTAQ (Hybrid Terrestrial and Aerial Quadrotor) robot developed at Illinois Institute of Technology (IIT)
Ever since the Huygens probe landed on Titan back in January 2005, sending us our first tantalizing and oh-so-brief glimpses of the moon’s murky, pebbly surface, researchers have been dreaming up ways to explore further… after all, what’s more intriguing than a world in our own Solar System that’s basically a miniature version of an early Earth (even if it’s quite a few orders of magnitude chillier?)
Many concepts have been suggested as to the best way to explore Titan, from Mars-style rovers to boats that would sail its methane seas to powered gliders… and even hot-air balloons have been put on the table. Each of these have their own specific benefits, specially suited to the many environments that are found on Titan, but what if you could have two-in-one; what if you could, say, rove and fly?
That’s what this little robot can do.
Designed by Arash Kalantari and Matthew Spenko at the Robotics Lab at Illinois Institute of Technology, this rolling birdcage is actually a quadrotor flying craft that’s wrapped in a protective framework, allowing it to move freely along the ground and then take off when needed, maneuvering around obstacles easily.
A design like this, fitted with scientific instruments and given adequate power supply, might make a fantastic robotic explorer for Titan, where the atmosphere is thick and the terrain may range from rough and rocky to sandy and slushy. (And what safer way to ford a freezing-cold Titanic stream than fly over it?)
Also, the robot’s cage design may make it better suited to travel across the frozen crust of Titan’s flood plains, which have been found to have a consistency like damp sand with a layer of frozen snow on top. Where wheels could break through and get permanently stuck (a la Spirit) a rolling cage might remain on top. And if it does break through… well, fire up the engines and take off.
The robot (as it’s designed now) is also very energy-efficient, compared to quadrotors that only fly.
“During terrestrial locomotion, the robot only needs to overcome rolling resistance and consumes much less energy compared to the aerial mode,” the IIT website notes. “This solves one of the most vexing problems of quadrotors and rotorcraft in general — their short operation time. Experimental results show that the hybrid robot can travel a distance 4 times greater and operate almost 6 times longer than an aerial only system.”
Of course this is all just excited speculation at this point. No NASA or ESA contracts have been awarded to IIT to build the next Titan explorer, and who knows if the idea is on anyone else’s plate. But innovations like this, from schools and the private sector, are just the sorts of exciting things that set imaginations rolling (and flying!)
Color view of Titan’s surface, captured by the Huygens probe after landing in January 2005. (NASA/JPL/ESA/University of Arizona)
This image from NASA’s Cassini spacecraft shows a vast river system on Saturn’s moon Titan. It is the first time images from space have revealed a river system so vast and in such high resolution anywhere other than Earth. Image Credit: NASA/JPL-Caltech/ASI
Titan is appearing more Earth-like all the time (yes, a very cold, and early version of Earth), as now the Cassini spacecraft has spotted what appears to be a miniature extraterrestrial version of the Nile River: a river valley on Saturn’s moon Titan that extends from what looks like ‘headwaters’ out to a large sea. Not only is it a riverbed, but it appears to be filled with liquid; likely very cold hydrocarbons such as ethane or methane.
Scientists deduce that the river is filled with liquid because it appears dark along its entire extent in the high-resolution radar image, indicating a smooth surface.
It is the first time images have revealed a river system this vast and in such high resolution anywhere beyond Earth.
“Though there are some short, local meanders, the relative straightness of the river valley suggests it follows the trace of at least one fault, similar to other large rivers running into the southern margin of this same Titan sea,” says Jani Radebaugh, a Cassini radar team associate at Brigham Young University, USA. “Such faults – fractures in Titan’s bedrock – may not imply plate tectonics, like on Earth, but still lead to the opening of basins and perhaps to the formation of the giant seas themselves.”
While the Earthly Nile River is 6,650 kilometers (4,132 miles) long, Titan’s big river is about 400 km long.
Titan is the only other world we know of that has stable liquid on its surface. While Earth’s hydrologic cycle relies on water, Titan’s equivalent cycle involves hydrocarbons.
Images from Cassini’s visible-light cameras in late 2010 revealed regions that darkened after recent rainfall.
Cassini’s visual and infrared mapping spectrometer confirmed liquid ethane at a lake in Titan’s southern hemisphere known as Ontario Lacus in 2008.
“This radar-imaged river by Cassini provides another fantastic snapshot of a world in motion, which was first hinted at from the images of channels and gullies seen by ESA’s Huygens probe as it descended to the moon’s surface in 2005,” said Nicolas Altobelli, ESA’s Cassini Project Scientist.
