Titan Archives

July 29, 2014December 23, 2015 by Ken Kremer

Scientists Discover 101 Geysers Erupting at Saturn’s Intriguing Icy Moon Enceladus

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 — 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 — 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 100 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 — 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.

Ken Kremer

June 30, 2014December 23, 2015 by Elizabeth Howell

Saturn’s Sailor: 20 Cassini Pictures Marking A Decade At The Ringed Planet

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.

And by the way, we’re not the only ones assembling memorable images to mark the anniversary. Check out NASA’s favourite Cassini pictures of the past decade, or our friend Phil Plait’s Bad Astronomy list. Also, here is NASA’s opinion of the top 10 discoveries at the ringed planet.

While thinking about Cassini, also don’t forget Huygens, the lander that descended to the surface of Titan in 2005. More on that in this past Universe Today anniversary story.

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/SSI — 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/SSI

Saturn, imaged by Cassini on approach. Credit: CICLOPS

Titan and Dione as seen by Cassini. Credit: NASA/JPL/Space Science Institute

Which Planets Have Rings? — This 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: NASA — 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: NASA

Raw image from Cassini on May 18. Credit: NASA/JPL/SSI

Hemispheric 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/SSI — Hemispheric 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/SSI

Three of Saturn's moons bunch together in this image by Cassini. Credit: NASA/JPL/Space Science Institute. Click for larger image. — Three 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/SS

Phoebe imaged by the Cassini spacecraft. Image Credit: NASA

Cassini 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.) — Cassini 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/SSI

Cassini captured this startling image of Saturn's moon Hyperion. Photo Credit: NASA/JPL — Cassini captured this startling image of Saturn’s moon Hyperion. Photo Credit: NASA/JPL

ets 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/SSI — ets 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/SSI

This 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 Arizona

This 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/SSI — This 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/SSI

Cassini came within 25 kilometers (15.6 miles) of the surface of Enceladus on Oct. 5, 2008. Image credit: NASA/JPL/Space Science Institute

June 24, 2014December 23, 2015 by Shannon Hall

Titan’s Atmosphere May be Older than Saturn, a New Study Suggests

Titan's atmosphere makes Saturn's largest moon look like a fuzzy orange ball in this natural-color view from the Cassini spacecraft. Cassini captured this image in 2012. Image Credit: NASA/JPL-Caltech/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.

June 23, 2014December 23, 2015 by Nancy Atkinson

‘Ghost’ Object Appears, Disappears on Titan

During previous flybys, 'Magic Island' was not visible near Ligeia Mare's coastline (left). Then, during Cassini's July 20, 2013, flyby the feature appeared (right)/ Credit: NASA/JPL-CALTECH/ASI/CORNELL, image editing via Ian O'Neill/Discovery News.

Astronomers with the Cassini mission have detected a bright, mysterious geologic object on Saturn’s moon Titan that suddenly showed up in images from the mission’s radar instrument. The object appeared in Ligeia Mare, the second-largest sea Titan. The feature looks like an island and so the team named it “Magic Island.” However, it most likely is not an island that suddenly surfaced. But scientists say this may be the first observation of dynamic, geological processes in Titan’s northern hemisphere.

The object suddenly showed up in images beamed back from Cassini on July 10, 2013, showing regions of Ligeia Mare, a sea located near Titan’s north pole. But then just as suddenly, in a follow-up flyby only days later on July 26, the island was gone. Subsequent flybys confirmed that Magic Island had vanished and is what is known as a “transient feature.”

“This discovery tells us that the liquids in Titan’s northern hemisphere are not simply stagnant and unchanging, but rather that changes do occur,” said Jason Hofgartner, a Cornell graduate student in the and the lead author of a paper appearing in Nature Geoscience. “We don’t know precisely what caused this ‘magic island’ to appear, but we’d like to study it further.”

Map of Titan's northern region of hydrocarbon 'seas' created from Cassini radar imaging. Credit: NASA/JPL/USGS. — Map of Titan’s northern region of hydrocarbon ‘seas’ created from Cassini radar imaging. Credit: NASA/JPL/USGS.

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.

So what was this object? Among the explanations from the team are:

Northern hemisphere winds may be kicking up and forming waves on Ligeia Mare. The radar imaging system might see the waves as a kind of “ghost” island. Scientists previously have seen what they think are waves in another nearby Titan sea, Punga Mare.

Gases may push out from the sea floor of Ligeia Mare, rising to the surface as bubbles.

Sunken solids formed by a wintry freeze could become buoyant with the onset of the late Titan spring warmer temperatures.

Suspended solids in Ligeia Mare, which are neither sunken nor floating, but act like silt in a terrestrial delta.

“Likely, several different processes – such as wind, rain and tides – might affect the methane and ethane lakes on Titan. We want to see the similarities and differences from geological processes that occur here on Earth,” Hofgartner said. “Ultimately, it will help us to understand better our own liquid environments here on the Earth.”

Source: Cornell University

June 16, 2014December 23, 2015 by Elizabeth Howell

New Recipe For Saturn’s Orangey Moon Titan Is ‘Aromatic’ And Hazy

A fish-eye view of Titan's surface from the European Space Agency's Huygens lander in January 2005. Credit: ESA/NASA/JPL/University of Arizona

What’s in all that browny orangey stuff in the atmosphere around Titan? It’s a question that scientists have been trying to answer concerning Saturn’s moon for decades (Carl Sagan was among them). That’s because it’s hard to reverse-engineer the recipe.

There are hundreds of thousands of hydrocarbons (hydrogen and carbon molecules) that could form the compounds in the atmosphere along with nitriles (nitrogen-abundant chemicals). But scientists are hoping that their new recipe gets a bit closer to understanding how the atmosphere works.

The researchers put gases inside of a chamber and monitored their reactions, starting with nitrogen and methane — the gases that are the most common in Titan’s atmosphere. Then they included benzene — which the Cassini spacecraft has detected in the atmosphere — along with close chemical relatives.

Titan's surface is almost completely hidden from view by its thick orange "smog" (NASA/JPL-Caltech/SSI. Composite by J. Major) — Titan’s surface is almost completely hidden from view by its thick orange “smog” (NASA/JPL-Caltech/SSI. Composite by J. Major)

In the end, it seemed the best third ingredient was choosing an “aromatic”, a sort of hydrocarbon, that includes nitrogen. That’s because the scientists saw that the spectrum of this gas appeared to be similar to what was spotted by Cassini.

“This is the closest anyone has come, to our knowledge, to recreating with lab experiments this particular feature seen in the Cassini data,” stated lead author Joshua Sebree, a former postdoctoral fellow at the NASA Goddard Space Flight Center who is now an assistant professor at the University of Northern Iowa in Cedar Falls.

Scientists say the recipe still needs some modifications, but this is a good start. The research is available in the journal Icarus.

Source: Jet Propulsion Laboratory

June 6, 2014December 23, 2015 by Elizabeth Howell

Titan Balloon Among Far-Out Concepts NASA Selects For Funding

Artist's conception of the Titan Aerial Daughtercraft on Titan, a moon of Saturn. Credit: NASA

Sometimes a good idea takes some tinkering. You have a thought that it will work, but what it really requires is you take some money and time and test it out in a small form. This principle is sound if you’re trying to do home renovation (a paint splash on a wall can let you see if the color will work) and it is especially true if you’re planning a multi-million dollar mission to another planet.

This is the thought behind the NASA Innovative Advanced Concepts office, which announced a dozen far-flung drawing-board proposals that received $100,000 in Phase 1 funding for the next 9-12 months. There are vehicles to explore the soupy moon of Titan, a design to snag a tumbling asteroid, and other ideas to explore the solar system. (But be patient: These testbed ideas would take decades to come to fruition, if they are even accepted for further study and funding.) Check out a full list of the concepts below.

Titan Aerial Daughtercraft: A small rotorcraft that can touch down from a balloon or lander, with the idea being that it can jump between several spots to do close-up views. It would then bring its samples back to the “mothership” and possibly recharge there as well. “The autonomy needed for this concept is also applicable to exciting rotorcraft mission concepts for Mars and to in-situ exploration of Enceladus,” the description stated, referring to an icy moon of Saturn.

Titan Submarine: A small submarine would dive into Kraken Mare on Saturn’s moon, and there would be plenty to explore: 984 feet (300 meters) of depth, stretching across 621 miles (1,000 km). “Kraken Mare is comparable in size to the Great Lakes and represents an opportunity for an unprecedented planetary exploration mission,” the description stated. It would explore “chemical composition of the liquid, surface and subsurface currents, mixing and layering in the ‘water’ column, tides, wind and waves, bathymetry, and bottom features and composition.”

Comet Hitchhiker: This would be a “tethered” spacecraft that swings from comet to comet to explore icy bodies in the solar system. “First, the spacecraft harpoons a target as it makes a close flyby in order to attach a tether to the target. Then, as the target moves away, it reels out the tether while applying regenerative brake to give itself a moderate (<5g) acceleration as well as to harvest energy,” the description stated.

Artist's conception of the Weightless Rendezvous And Net Grapple to Limit Excess Rotation (WRANGLER). Credit: NASA — Artist’s conception of the Weightless Rendezvous And Net Grapple to Limit Excess Rotation (WRANGLER). Credit: NASA

Weightless Rendezvous And Net Grapple to Limit Excess Rotation (WRANGLER): This idea would capture space debris and small asteroids. It will use a small nanosatellite equipped with a “net capture device” and a winch. “The leverage offered by using a tether to extract angular momentum from a rotating space object enables a very small nanosatellite system to de-spin a very massive asteroid or large spacecraft,” the description stated.

The Aragoscope: A telescope that would look through an opaque disk at a distant object, which is different from the usual mirror arrangement.”Rather than block the view, the disk boosts the resolution of the system with no loss of collecting area,” the description states. This architecture … can be used to achieve the diffraction limit based on the size of the low cost disk, rather than the high cost telescope mirror.”

Mars Ecopoiesis Test Bed: A machine that would test how well bacteria from Earth could survive on Mars, which could be a precursor to “terraforming” the planet to make it more like our own. Researchers would select “pioneer organisms” and put them into a device that would embed itself into the Martian regolith (soil) in an area that would have liquid water. It would “completely seal itself to avoid planetary contamination, release carefully selected earth organisms (extremophiles like certain cyanobacteria), sense the presence or absence of a metabolic product (like O2), and report to a Mars-orbiting relay satellite,” the description states.

Artist's conception of ChipSats. Credit: NASA — Artist’s conception of ChipSats. Credit: NASA

ChipSats: Instead of having an orbiter and a lander in separate missions, why not put them in one? While there have been combinations before (e.g. Cassini/Huygens), this is a bit different: This concept would have a set of tiny sensor chips (ChipSats) that deploy from a larger mothership to make a landing on a distant planet or moon.

Swarm Flyby Gravimetry: While whizzing by a comet or asteroid, a single spacecraft would release a swarm of tiny probes. “By tracking those probes, we can estimate the asteroid’s gravity field and infer its underlying composition and structure,” the description stated.

Probing icy worlds concept: How thick is the ice on Jupiter’s Europa or Ganymede, or Saturn’s Enceladus? Open question, and makes it hard to predict how tough of a drill one would need to probe the ice — or how well life could survive. This concept would send a probe to one of these locations and receive “a naturally occurring signal generated by interactions of deep penetrating cosmic ray neutrinos” to better get a sense of the depth. This could allow for maps of the ice.

The cracked ice surface of Europa. Credit: NASA/JPL

Heliopause Electrostatic Rapid Transit System (HERTS): This would be a mission that goes deep into the solar-system and out to the heliopause, the spot where the sun’s sphere of influence gives way to the interstellar medium. Using no propellant, the spacecraft would use solar wind protons to bring it out into the solar system. “The propulsion system consists of an array of electrically biased wires that extend outward 10 to 30 km [6.2 miles to 18.6 miles] from a rotating spacecraft,” the researchers stated.

3D Photocatalytic Air Processor: A new design to make it easier to generate oxygen on a spacecraft, using “abundant high-energy light in space,” the proposal states. ” The combination of novel photoelectrochemistry and 3-dimensional design allows tremendous mass saving, hardware complexity reduction, increases in deployment flexibility and removal efficiency.”

PERIapsis Subsurface Cave OPtical Explorer (PERISCOPE): A way to probe caves on the moon from orbit. Using a concept called “photon time-of-flight imaging”, the researchers say they would be able to bounce the signal off of the walls of the canyon to peer into the crevice and see what is there.

May 29, 2014December 23, 2015 by Elizabeth Howell

How Much Can Titan’s Sunsets Teach Us About Alien Planets?

An illustration of a Titanic lake by Ron Miller. All rights reserved. Used with permission.

Titan — that smoggy, orangy moon circling Saturn — is of great interest to exobiologists because its chemistry could be good for life. It has a thick atmosphere of nitrogen and methane and likely has lakes filled with liquid hydrocarbons, and scientists believe there is enough light filtering down into the atmosphere to drive chemical reactions.

It turns out the moon could also be a good analog to help us understand the atmospheres of exoplanets far beyond our solar system. From looking at sunsets on the moon, scientists led by NASA believe that a thick atmosphere could influence how we perceive a planet from afar.

First, a bit of information about how scientists learn about planet atmospheres in the first place. When a distant planet passes in front of its parent star, the light from the star passes through the atmosphere and gets distorted.

The spectra that telescopes pick up can then tell scientists information about what the atmosphere is made of, what temperature it is, and how it is structured. (This science, it should be noted, is in its very early stages and works best on very large exoplanets that are relatively close to Earth, since the planets are so small and far away.)

“Previously, it was unclear exactly how hazes were affecting observations of transiting exoplanets,” stated Tyler Robinson, a postdoctoral research fellow at NASA’s Ames Research Center who led the research. “So we turned to Titan, a hazy world in our own solar system that has been extensively studied by Cassini.”

To do this, Robinson’s team used data from the Cassini spacecraft during four solar occultations, or times when Titan passed in front of our own sun from the perspective of the spacecraft. They found out that the moon’s hazy atmosphere makes it difficult to figure out what is in its spectra.

“The observations might be able to glean information only from a planet’s upper atmosphere,” NASA stated. “On Titan, that corresponds to about 90 to 190 miles (150 to 300 kilometers) above the moon’s surface, high above the bulk of its dense and complex atmosphere.”

The haze is even more powerful in the shorter (bluer) wavelengths of light, which contradicts previous studies assuming that all wavelengths of light would have the same distortions. Models of exoplanet atmospheres usually have simplified spectra because hazes are complex to model, requiring a lot of computer power.

Researchers hope to take these observations of Titan and then use them to better inform how exoplanet models are created.

The research was published May 26 in the Proceedings of the National Academy of Science.

Source: NASA

May 12, 2014December 23, 2015 by Bob King

Saturn Disappears Behind the Full Flower Moon May 14 – Watch it Live

Simulation of the moon closing in on Saturn just prior to occultation. Credit: Gianluca Masi using SkyX software

Funny thing. Skywatchers are often just as excited to watch a celestial object disappear as we are to see it make an appearance. Early Wednesday morning (May 14) the Full Flower Moon will slip in front of Saturn, covering it from view for about an hour for observers in Australia and New Zealand. If you don’t live where the dingoes roam, no worries. You can watch it online.And no matter where you are on the planet, the big moon will accompany the ringed planet across the sky this Tues. night-Weds. morning.

Moon-Saturn occultation from Perth, Australia Feb. 22, 2014 captured by Colin Legg

Occultations of stars happen swiftly. The moon’s limb meets the pinpoint star and bam! it’s gone in a flash. But Saturn is an extended object and the moon needs time to cover one end of the rings to the other. Planetary occultations afford the opportunity to remove yourself from planet Earth and watch a planet ‘set’ and ‘rise’ over the alien lunar landscape. Like seeing a Chesley Bonestell painting in the flesh.

Saturn and the moon tomorrow night just before midnight as viewed from the Midwestern U.S. View faces south-southeast. Stellarium — Saturn and the moon Tuesday night (May 13) just before midnight as viewed from the U.S. Stellarium

As the moon approaches Saturn, the planet first touches the lunar limb and then appears to ‘set’ as it’s covered by degrees. About an hour later, the planet ‘rises’ from the opposite limb. Planetary occultations are infrequent and always worth the effort to see.

Seen from the northern hemisphere and equatorial regions, the nearly full moon will appear several degrees to the right or west of Saturn tomorrow night (May 13). As the night deepens and the moon rolls westward, the two grow closer and closer. They’ll be only a degree apart (two full moon diameters) during Wednesday morning twilight seen from the West Coast. Northern hemisphere viewers will notice that the moon slides to the south of the planet overnight.

Map showing the region where the occultation of Saturn will be visible. Click to get the times of Saturn's disappearance and reappearance for individual cities. Times are given in UT or Universal Time. Add 9.5 hours for Australian Central Standard Time. Credit: IOTA — Map showing the region where the occultation of Saturn will be visible. Click to get times of Saturn’s disappearance and reappearance for individual cities. Times shown are UT or Universal Time. Add 9.5 hours for Australian Central Standard Time. Credit: IOTA

Skywatchers in Australia will see the moon cover Saturn during convenient early evening viewing hours May 14:

* 8:09 p.m. local time from Adelaide

* 9:05 p.m. Brisbane

* 8:50 p.m. Melbourne

* 8:53 p.m. Canberra

* 8:56 p.m. from Sydney (More times and a map – click HERE)

Before the occultation, Saturn will shine close to the moon’s upper right and might be tricky to see with the naked eye because of glare.

Binoculars will easily reveal the planet, but a telescope is the instrument of choice. Even a small scope magnifying at least 30x will show Saturn and its rings hovering above the bright edge of the moon. Stick around. About an hour later, Saturn will re-emerge along the moon’s lower left limb.

Saturn and its moons Tuesday night May 13 around 10 p.m. CDT. Titan's the brightest and easiest. Iapetus ranges from magnitude +10 when it's west of Saturn and we see its bright hemisphere to magnitude +12 when it's west of the planet as it will be this week. Created with Meridian software — Saturn and its moons Tuesday night May 13 around 10 p.m. CDT. Titan’s the brightest and easiest moon to see at magnitude +8.5. Iapetus ranges from magnitude +10 when it’s west of Saturn and we see its bright hemisphere to magnitude +12 when it’s east of the planet. Created with Meridian software

Meanwhile, back in the western hemisphere, we’ll watch the nearly full Flower Moon make a close pass of the planet. If you’ve had difficulty finding the celestial ring bearer, you’ll have no problem Tuesday night. Take a look at Saturn’s wonderful system of rings in your telescope – they’re tipped nearly wide open this year. For even more fun, see how many moons you can spot. And don’t forget, you can watch it online courtesy of astrophysicist Gianluca Masi. His Virtual Telescope website will broadcast the occultation live starting at 10:15 Universal Time May 14 (6:15 a.m. EDT, 5:15 CDT, 4:15 MDT and 3:15 PDT).

April 15, 2014December 23, 2015 by Michael Habib

Let’s Put a Sailboat on Titan

An illustration showing how a sailboat mission to Titan might land and become operational. Copyright: Estevan Guzman for Universe Today.

The large moons orbiting the gas giants in our solar system have been getting increasing attention in recent years. Titan, Saturn’s largest moon, is the only natural satellite known to house a thick atmosphere. It’s surface, revealed in part by the Cassini probe, is sculpted by lakes and rivers. There is interest in exploring Titan further, but this is tricky from orbit because seeing through the thick atmosphere is difficult. Flying on Titan has been discussed around the web (sometimes glibly), and this was even one of the subjects treated by the immensely popular comic, XKCD.

However, there remains the problem of powering propulsion. The power requirements for flight are quite minimal on Titan, so solar wings might work. But Titan also presents an alternative: sailing.

Images from the Cassini mission show river networks draining into lakes in Titans north polar region. Credit: NASA/JPL/USGS.

With all those lakes and rivers, exploring Titan with a surface ship might be a great way to see much of the moon. The vehicle wouldn’t be sailing on water, though. The lakes on Titan are composed of liquid methane. The challenge is therefore making the vessel buoyant: liquid methane is only 45% as dense as liquid water. This means we would need a lot of displacement. A deep, hollow hull could do this, however, and it turns out that the liquid methane has an advantage that helps make up for the low density: it is much less viscous than water.

Reynolds number is proportional to the ratio of density to viscosity, and it turns out that friction drag on a hull is inversely proportional to Re. While Titan’s seas and lakes have only 45% the density of water, they also have only 8% of the viscosity. This means that the Titan sailing vessel would only experience about 26% of the friction drag as its Earth equivalent. [Yacht designers have found that the friction drag is about equal to 0.075/(log(Re)-2)^2)]. That leaves us room to make the hull deeper (important to compensate for the density as above), and longer (if we want a longer waterline, which will make the bow waves longer and improve maximum speed).

The sail itself would get less wind, on average, on Titan than Earth. Average wind speeds on Titan seem to be about 3 meters/s, according to Cassini, though it might be higher over the lakes. Average wind speed over Earth oceans is closer to 6.6 meters/s. But, the Titan atmosphere is also about 4x denser than Earth’s, and both lift and drag are proportional to fluid density. All told, this means that the total fluid force on the sail will be about 83% of what you’d get on Earth, all else being equal, which could be sufficient. There would be a premium on sail efficiency and size, and so we might have to take advantage of the low-friction hull to examine shapes with more stability that can house a larger, taller (and presumably high aspect ratio) sail.

This is all quite speculative, of course, but it provides a fun exercise and perhaps provides inspiration as we imagine tall-sailed robotic vessels silently cruising the lakes of Titan.

Titan Mare Explorer. Image credit: NASA/JPL

One concept for a boat on Titan has already been proposed: the Titan Mare Explorer (TiME) would send a floating high-tech buoy to land in a methane sea on this moon of Saturn to study its composition and its interaction with the atmosphere. But this Discovery-class mission concept was nixed in favor of sending the InSight lander to Mars.

But with all the recent discoveries on Titan by the Cassini spacecraft — things like lakes, seas, rivers and weather and climate patterns that create both fog and rain — a mission like this will be given more consideration in the future.

April 8, 2014December 23, 2015 by Jason Major

Cassini Sees a “Zen Garden” on Titan

Radar image of rows of dunes on Titan. Credit: NASA/JPL-Caltech

Looking like the flowing designs carved by a Zen gardener’s rake, long parallel dunes of hydrocarbon sand stretch across the surface of Saturn’s moon Titan. The image above, acquired by Cassini in July 2013, reveals these intriguing and remarkably Earthlike landforms in unprecedented detail via radar, which can easily pierce through Titan’s thick clouds.

I’m feeling a little more enlightened already.

Although it piles into dunes like sand does here, Titan’s sand is not the same as what you’d find on a beach here on Earth. According to an ESA “Space in Images” article:

While our sand is composed of silicates, the ‘sand’ of these alien dunes is formed from grains of organic materials about the same size as particles of our beach sand. The small size and smoothness of these grains means that the flowing lines carved into the dunes show up as dark to the human eye.

Radar imaging, although capable of seeing through Titan’s opaque orange atmosphere, doesn’t capture visible-light images. Instead it’s sensitive to the varying textures of a landscape as they reflect microwaves; the smoother an object or an area is the darker it appears to radar, while irregular, rugged terrain shows up radar-bright.

The pixelated “seam” cutting horizontally across the center is the result of image artifacting.

Learn more about Cassini’s RADAR instrument here, and read more about this image on the ESA site here.