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.
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.
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?
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!”
Icy volcanoes are likely responsible for changes in brightness on the surface of Titan, the largest moon of Saturn, according to a new study.
Images with the Cassini spacecraft’s visual and infrared mapping spectrometer revealed the brightness, or albedo, of two equatorial areas changing during the study period. Tui Regio (which got darker from 2005 to 2009) and Sotra Patera (which got brighter from 2005 to 2006).
The researchers also pointed to “volcanic-like features” in these areas as evidence that the potential cryovolcanoes, as these icy volcanoes are known, might be connected to an ocean on Titan.
“All of these features, plus a need for a methane reservoir and volcanic activity to replenish the methane in the atmosphere, is compatible with the theory of active cryovolcanism on Titan,” stated Anezina Solomonidou , a planetary geologist with the Paris Observatory as well as the National and Kapodistrian University of Athens.
“These results have important implications for Titan’s potential to support life, as these cryovolcanic areas might contain environments that could harbor conditions favorable for life,” Solomonidou added.
Of note, Titan also has a fresh-looking surface with few craters on it, indicating that something might be altering the surface. “Its landscape is remarkably Earth-like with dunes and lakes, erosion due to weathering and tectonic-like features,” a statement on the research added.
There’s been chatter about cryovolcanoes on Titan before. In 2010, researchers said a chain of peaks found on the moon could be evidence of this type of feature. However, a 2012 preliminary California Institute of Technology weather model of the moon explained many of its features without necessarily needing to rely on cryovolcanoes.
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)
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.
In this image acquired on January 5, Cassini’s near-infrared vision pierced Titan’s opaque clouds to get a glimpse of the dark dune fields across a region called Senkyo.
The vast sea of dunes is composed of solid hydrocarbon particles that have precipitated out of Titan’s atmosphere. Also visible over Titan’s southern pole are the rising clouds of the recently-formed polar vortex.
For a closer look at Titan’s dunes (and to find out what the name Senkyo means) keep reading…
In the image above north on Titan is up and rotated 18 degrees to the right. It was taken using a spectral filter sensitive to wavelengths of near-infrared light centered at 938 nanometers.
The view was obtained at a distance of approximately 750,000 miles (1.2 million kilometers) from Titan.
Titan’s hydrocarbon dunes are found across the moon in a wide swath within 30 degrees of the equator and are each about a kilometer wide and tens to hundreds of kilometers long… and in some cases stand over 100 meters tall. (Source: Astronomy Now.)
Observations of the dunes with Cassini and ESA’s Huygens probe during its descent onto Titan’s surface have shown that the moon experiences seasonally-shifting equatorial winds during equinoxes, similar to what occurs over the Indian Ocean between monsoon seasons.
The name Senkyo refers to the Japanese realm of serenity and freedom from wordly cares and death… in line with the IAU convention of naming albedo features on Titan after mythological enchanted places.
Click here for an earlier view of Senkyo, and follow the Cassini mission here.
A star party favorite is about to return to evening skies.
The planet Saturn can now be spied low to the southeast for northern hemisphere observers (to the northeast for folks in the southern) rising about 1-2 hours after local sunset this early April. That gap will continue to close until Saturn is opposite to the Sun in the sky later this month and rises as the Sun sets.
Opposition occurs on April 28th at 8:00 UT/4:00AM EDT. Saturn will shine at magnitude +0.1 and appear 18.8” in diameter excluding the rings, which give it a total angular diameter of 43”.
Saturn has just passed into the faint constellation Libra for 2013, although its springtime retrograde loop will bring it back into Virgo briefly. Both the 2013 and 2014 opposition will occur in Libra. Saturn will also pass 26’ from +4.2 Kappa Virginis on July 3rd as it moves back into Virgo while in retrograde before resuming direct motion back into Libra.
Saturn currently lies about 15° to the lower left of the +1.04 magnitude star Spica, also known as Alpha Virginis. Remember the handy saying to “Spike to Spica” from the handle of the Big Dipper asterism to locate the region. Another handy finder tip; stars twinkle, planet generally don’t. That is, unless your skies are extremely turbulent!
With an orbital period 29.46 years, Saturn moves slowly eastward year to year, taking 2-3 years to cross through each constellation along the ecliptic.
Oppositions are roughly 378 days apart and thus move forward on our calendar by about two weeks a year. Successive oppositions also move about 13° eastward per year.
Oppositions of the ringed planet are also currently becoming successively favorable for southern observers over the coming years. Saturn crossed into the southern celestial hemisphere some years back, and will be at its southernmost in 2018.
Saturn won’t pass north of the celestial equator again until early 2026. Saturn is 15 million kilometres farther from us than opposition last year as its moving toward aphelion in 2018.
Saturn will reach eastern quadrature this summer on July 28th and stand its highest south at sunset northern hemisphere observers. South of the equator, it will pass directly overhead or transit to the north. Saturn will be with us for most of the remainder of 2013 in evening skies until reaching solar conjunction on November 6th.
Looking at Saturn with binoculars, you’ll immediately note that something is amiss.
You’re getting a view similar to that of Galileo, who sketched Saturn as a sort of “double handled cup.” In fact, it wasn’t until 1655 that Christian Huygens correctly hypothesized that the rings of Saturn are a flat disk that is not physically in contact with the planet.
Huygens also discovered the large moon Titan. Shining at magnitude +8.5 and taking 16 days to orbit Saturn, Titan is the second largest moon in our solar system after Ganymede. Titan would easily be a planet in its own right if it orbited the Sun. Titan is easily picked out observing Saturn at low power through a telescope.
Observing Saturn at slightly higher magnification, five moons interior to Titan become apparent. From outside in, they are Rhea, Dione, Tethys, Enceladus, and Mimas. Exterior to Titan is the curious moon of Iapetus. Taking 79 days to complete one orbit of Saturn, Iapetus varies in brightness from magnitude +11.9 to +10.2, or a factor of over 5 times. Arthur C. Clarke placed the final monolith in the book adaptation of 2001: A Space Odyssey on Iapetus for this reason. Close-ups from the Cassini spacecraft reveal a two-faced world covered with a dark leading hemisphere and a bright trailing side, but alas, no alien artifacts.
But the centerpiece of observing Saturn through a telescope is its brilliant and complex system of rings. The A, B, and C rings are easily apparent through a backyard telescope, as is the large spacing known as the Cassini Gap.
The rings are also currently tilted in respect to our Earthly vantage point. The rings were edge-on in 2009 and vanish when this occurs every 15-16 years.
This year, we see the rings of Saturn at a respectable 19 ° opening and widening. The rings will appear at their widest at over 25° in 2017 and then become edge-on again in 2025.
The ring system of Saturn adds 0.7 magnitudes of overall brightness to the planet at opposition this year.
Another interesting optical phenomenon to watch for in the days leading up to opposition is known as the “opposition surge” in brightness, or the Seeliger effect. This is a retro-reflector effect familiar to many as high-beam headlights strike a highway sign. Think of the millions of particles making up Saturn’s rings as tiny little “retro-reflectors” focusing sunlight back directly along our line of sight. The opposition surge has been noted for other planets, but it’s most striking for Saturn when its rings are at their widest.
The disk of Saturn will cast a shadow straight back onto the rings around opposition and thus vanish from our view. The shadow across the back of the rings will then become more prominent over subsequent months, reaching its maximum angle at quadrature this northern hemisphere summer and then beginning to slowly slide back behind the planet again. A true challenge is to glimpse the disk of the through the Cassini gap in the rings… you’ll need clear steady skies and high magnification for this one!
It’s also interesting to note a very shallow partial lunar eclipse occurs with Saturn nearby just three days prior to opposition on April 25th. Saturn will appear 4° north of the Moon and it may be just possible to image both in the same frame.
Saturn takes about 30 years to make its way around the zodiac. I remember just beginning to observe Saturn will my new 60mm Jason refractor as a teenager in 1983 as it crossed the constellation Virgo.Hey, I’ve been into astronomy for over one “Saturnian year” now… where will the next 30 years find us?
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.
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)