Titan Archives

October 19, 2017October 19, 2017 by Matt Williams

Forecast for Titan: Cold, with a Chance of Noxious Ice Clouds

This view of Saturn’s largest moon, Titan, is among the last images the Cassini spacecraft sent to Earth before it plunged into the giant planet’s atmosphere. Credits: NASA/JPL-Caltech/Space Science Institute

During the 13 years and 76 days that the Cassini mission spent around Saturn, the orbiter and its lander (the Huygens probe) revealed a great deal about Saturn and its systems of moons. This is especially true of Titan, Saturn’s largest moon and one of the most mysterious objects in the Solar System. As a result of Cassini’s many flybys, scientists learned a great deal about Titan’s methane lakes, nitrogen-rich atmosphere, and surface features.

Even though Cassini plunged into Saturn’s atmosphere on September 15th, 2017, scientists are still pouring over the things it revealed. For instance, before it ended its mission, Cassini captured an image of a strange cloud floating high above Titan’s south pole, one which is composed of toxic, hybrid ice particles. This discovery is another indication of the complex organic chemistry occurring in Titan’s atmosphere and on it’s surface.

Since this cloud was invisible to the naked eye, it was only observable thanks to Cassini’s Composite Infrared Spectrometer (CIRS). This instrument spotted the cloud at an altitude of about 160 to 210 km (100 to 130 mi), far above the methane rain clouds of Titan’s troposphere. It also covered a large area near the south pole, between 75° and 85° south latitude.

*Artist concept of Cassini’s last moments at Saturn. Credit: NASA/JPL.*

Using the chemical fingerprint obtained by the CIRS instrument, NASA researchers also conducted laboratory experiments to reconstruct the chemical composition of the cloud. These experiments determined that the cloud was composed of the organic molecules hydrogen cyanide and benzene. These two chemicals appeared to have condensed together to form ice particles, rather than being layered on top of each other.

For those who have spent more than the past decade studying Titan’s atmosphere, this was a rather interesting and unexpected find. As Carrie Anderson, a CIRS co-investigator at NASA’s Goddard Space Flight Center, said in a recent NASA press statement:

“This cloud represents a new chemical formula of ice in Titan’s atmosphere. What’s interesting is that this noxious ice is made of two molecules that condensed together out of a rich mixture of gases at the south pole.”

The presence of this cloud around Titan’s southern pole is also another example of the moon’s global circulation patterns. This involves currents of warm gases being sent from the hemisphere that is experiencing summer to the hemisphere experience winter. This pattern reverse direction when the seasons change, which leads to a buildup of clouds around whichever pole is experiencing winter.

*Artist’s impression of Saturn’s moon Titan shows the change in observed atmospheric effects before, during and after equinox in 2009. Credit: NASA*

When the Cassini orbiter arrived at Saturn in 20o4, Titan’s northern hemisphere was experiencing winter – which began in 2004. This was evidenced by the buildup of clouds around its north pole, which Cassini spotted during its first encounter with the moon later than same year. Similarly, the same phenomena was taking place around the south pole near the end of Cassini’s mission.

This was consistent with seasonal changes on Titan, which take place roughly every seven Earth years – a year on Titan lasts about 29.5 Earth years. Typically, the clouds that form in Titan’s atmosphere are structured in layers, where different types of gas will condense into icy clouds at different altitudes. Which ones condense is dependent on how much vapor is present and temperatures – which become steadily colder closer to the surface.

However, at times, different types of clouds can form over a range of altitudes, or co-condense with other types of clouds. This certainly appeared to be the case when it came to the large cloud of hydrogen cyanide and benzene that was spotted above the south pole. Evidence of this cloud was derived from three sets of Titan observations made with the CIRS instrument, which took place between July and November of 2015.

The CIRS instrument works by separating infrared light into its constituent colors, and then measures the strengths of these signals at the different wavelengths to determine the presence of chemical signatures. Previously, it was used to identify the presence of hydrogen cyanide ice clouds over the south pole, as well as other toxic chemicals in the moon’s stratosphere.

*Artist’s impression of the Cassini orbiter’s Composite Infrared Spectrometer (CIRS). Credit: NASA-JPL*

As F. Michael Flasar, the CIRS principal investigator at Goddard, said:

“CIRS acts as a remote-sensing thermometer and as a chemical probe, picking out the heat radiation emitted by individual gases in an atmosphere. And the instrument does it all remotely, while passing by a planet or moon.”

However, when examining the observation data for chemical “fingerprints”, Anderson and her colleagues noticed that the spectral signatures of the icy cloud did not match those of any individual chemical. To address this, the team began conducting laboratory experiments where mixtures of gases were condensed in a chamber that simulated conditions in Titan’s stratosphere.

After testing different pairs of chemicals, they finally found one which matched the infrared signature observed by CIRS. At first, they tried letting one gas condense before the other, but found that the best results were obtained when both gases were introduced and allowed to condense at the same time. To be fair, this was not the first time that Anderson and her colleagues had discovered co-condensed ice in CIRS data.

For example, similar observations were made near the north pole in 2005, about two years after the northern hemisphere experienced its winter solstice. At that time, the icy clouds were detected at a much lower altitude (below 150 km, or 93 mi) and showed chemical fingerprints of hydrogen cyanicide and caynoacetylene – one of the more complex organic molecules in Titan’s atmosphere.

*Artist’s impression of the Cassini orbiter entering Saturn’s atmosphere. Credit: NASA/JPL*

This difference between this and the latest detection of a hybrid cloud, according to Anderson, comes down to differences in seasonal variations between the north and south poles. Whereas the northern polar cloud observed in 2005 was spotted about two years after the northern winter solstice, the southern cloud Anderson and her team recently examined was spotted two years before the southern winter solstice.

In short, it is possible that the mixture of the gases was slightly different in the two case, and/or that the northern cloud had a chance to warm slightly, thus altering its composition somewhat. As Anderson explained, these observations were made possible thanks to the many years that the Cassini mission spent around Saturn:

“One of the advantages of Cassini was that we were able to flyby Titan again and again over the course of the thirteen-year mission to see changes over time. This is a big part of the value of a long-term mission.”

Additional studies will certainly be needed to determine the structure of these icy clouds of mixed composition, and Anderson and her team already have some ideas on how they would look. For their money, the researchers expect these clouds to be lumpy and disorderly, rather than well-defined crystals like the single-chemical clouds.

In the coming years, NASA scientists are sure to be spending a great deal of time and energy sorting through all the data obtained by the Cassini mission over the course of its 13-year mission. Who knows what else they will detect before they have exhausted the orbiter’s vast collections of data?

Future Reading: NASA

October 18, 2017October 25, 2017 by Fraser Cain

Weekly Space Hangout – Oct 18, 2017: Weekly News Roundup

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October 16, 2017 by Matt Williams

Scientists Find Evidence of Extreme Methane Storms On Titan

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

Saturn’s largest moon, Titan, is a mysterious place; and the more we learn about it, the more surprises it seems to have in store. Aside from being the only body beyond Earth that has a dense, nitrogen-rich atmosphere, it also has methane lakes on its surface and methane clouds in its atmosphere. This hydrological-cycle, where methane is converted from a liquid to a gas and back again, is very similar to the water cycle here on Earth.

Thanks to the NASA/ESA Cassini-Huygens mission, which concluded on September 15th when the craft crashed into Saturn’s atmosphere, we have learned a great deal about this moon in recent years. The latest find, which was made by a team of UCLA planetary scientists and geologists, has to do with Titan’s methane rain storms. Despite being a rare occurrence, these rainstorms can apparently become rather extreme.

The study which details their findings, titled “Regional Patterns of Extreme Precipitation on Titan Consistent with Observed Alluvial Fan Distribution“, recently appeared in the scientific journal Nature Geoscience. Led by Saun P. Faulk, a graduate student at UCLA’s Department of Earth, Planetary, and Space Sciences, the team conducted simulations of Titan’s rainfall to determine how extreme weather events have shaped the moon’s surface.

What they found was that the extreme methane rainstorms may imprint the moon’s icy surface in much the same way that extreme rainstorms shape Earth’s rocky surface. On Earth, intense rainstorms play an important role in geological evolution. When rainfall is heavy enough, storms can trigger large flows of water that transport sediment into low lands, where it forms cone-shaped features known as alluvial fans.

During it’s mission, the Cassini orbiter found evidence of similar features on Titan using its radar instrument, which suggested that Titan’s surface could be affected by intense rainfall. While these fans are a new discovery, scientists have been studying the surface of Titan ever since Cassini first reached the Saturn system in 2006. In that time, they have noted several interesting features.

These included the vast sand dunes that dominate Titan’s lower latitudes and the methane lakes and seas that dominate it’s higher latitudes – particularly around the northern polar region. The seas – Kraken Mare, Ligeia Mare, and Punga Mare – measure hundreds of km across and up to several hundred meters deep, and are fed by branching, river-like channels. There are also many smaller, shallower lakes that have rounded edges and steep walls, and are generally found in flat areas.

In this case, the UCLA scientists found that the alluvial fans are predominantly located between 50 and 80 degrees latitude. This puts them close to the center of the northern and southern hemispheres, though slightly closer to the poles than the equator. To test how Titan’s own rainstorms could cause these features, the UCLA team relied on computer simulations of Titan’s hydrological cycle.

*False-color mosaic of Titan’s northern lakes, made from infrared data collected by NASA’s Cassini spacecraft. Credit: NASA*

What they found was that while rain mostly accumulates near the poles – where Titan’s major lakes and seas are located – the most intense rainstorms occur near 60 degrees latitude. This corresponds to the region where alluvial fans are most heavily concentrated, and indicates that when Titan does experience rainfall, it is quite extreme – like a seasonal monsoon-like downpour.

As Jonathan Mitchell – a UCLA associate professor of planetary science and a senior author of the study – indicated, this is not dissimilar to some extreme weather events that were recently experienced here on Earth. “The most intense methane storms in our climate model dump at least a foot of rain a day, which comes close to what we saw in Houston from Hurricane Harvey this summer,” he said.

The team also found that on Titan, methane rainstorms are rather rare, occurring less than once per Titan year – which works out to 29 and a half Earth years. But according to Mitchell, who is also the principal investigator of UCLA’s Titan climate modeling research group, this is more often than they were expecting. “I would have thought these would be once-a-millennium events, if even that,” he said. “So this is quite a surprise.”

In the past, climate models of Titan have suggested that liquid methane generally concentrates closer to the poles. But no previous study has investigated how precipitation might cause sediment transport and erosion, or shown how this would account for various features observed on the surface. As a result, this study also suggests that regional variations in surface features could be caused by regional variations in precipitation.

On top of that, this study is an indication that Earth and Titan have even more in common than previously thought. On Earth, contrasts in temperature are what lead to intense seasonal weather events. In North America, tornadoes occur during the early to late Spring, while blizzards occur during the winter. Meanwhile, temperature variations in the Atlantic ocean are what lead to hurricanes forming between the summer and fall.

Similarly, it appears that on Titan, serious variations in temperature and moisture are what triggers extreme weather. When cooler, wetter air from the higher latitudes interacts with warmer, drier air from the lower latitudes, intense rainstorms result. These findings are also significant when it comes to other bodies in our Solar System that have alluvial fans on them – such as Mars.

In the end, understanding the relationship between precipitation and planetary surfaces could lead to new insights about the impact climate change has on Earth and the other planets. Such knowledge would also go a long way towards helping us mitigate the effects it is having here on Earth, where the changes are only unnatural, but also sudden and very hazardous.

And who knows? Someday, it could even help us to alter the environments on other planets and bodies, thus making them more suitable for long-term human settlement (aka. terraforming)!

Further Reading: UCLA, Nature

October 12, 2017October 12, 2017 by Matt Williams

Ancient Hydrothermal Vents Found on Mars, Could Have Been a Cradle for Life

MOLA topographic data, colorized to show the maximum (1,100?m) and minimum (700?m) level of an ancient sea. Credit: NASA/Joseph R. Michalski (et al.)/Nature Communications

It is now a well-understood fact that Mars once had quite a bit of liquid water on its surface. In fact, according to a recent estimate, a large sea in Mars’ southern hemisphere once held almost 10 times as much water as all of North America’s Great Lakes combined. This sea existed roughly 3.7 billion years ago, and was located in the region known today as the Eridania basin.

However, a new study based on data from NASA’s Mars Reconnaissance Orbiter (MRO) detected vast mineral deposits at the bottom of this basin, which could be seen as evidence of ancient hot springs. Since this type of hydrothermal activity is believed to be responsible for the emergence of life on Earth, these results could indicate that this basin once hosted life as well.

The study, titled “Ancient Hydrothermal Seafloor Deposits in Eridania Basin on Mars“, recently appeared in the scientific journal Nature Communications. The study was led by Joseph Michalski of the Department of Earth Sciences and Laboratory for Space Research at the University of Hong Kong, along with researchers from the Planetary Science Institute, the Natural History Museum in London, and NASA’s Johnson Space Center.

*The Eridania basin of southern Mars is believed to have held a sea about 3.7 billion years ago, with seafloor deposits likely resulting from underwater hydrothermal activity. Credit: NASA*

Together, this international team used data obtained by the MRO’s Compact Reconnaissance Spectrometer for Mars (CRISM). Since the MRO reached Mars in 2006, this instrument has been used extensively to search for evidence of mineral residues that form in the presence of water. In this respect, CRISM was essential for documenting how lakes, ponds and rivers once existed on the surface of Mars.

In this case, it identified massive mineral deposits within Mars’ Eridania basin, which lies in a region that has some of the Red Planet’s most ancient exposed crust. The discovery is expected to be a major focal point for scientists seeking to characterize Mars’ once-warm and wet environment. As Paul Niles of NASA’s Johnson Space Center said in a recent NASA press statement:

“Even if we never find evidence that there’s been life on Mars, this site can tell us about the type of environment where life may have begun on Earth. Volcanic activity combined with standing water provided conditions that were likely similar to conditions that existed on Earth at about the same time — when early life was evolving here.”

Today, Mars is a cold, dry place that experiences no volcanic activity. But roughly 3.7 billion years ago, the situation was vastly different. At that time, Mars boasted both flowing and standing bodies of water, which are evidenced by vast fluvial deposits and sedimentary basins. The Gale Crater is a perfect example of this since it was once a major lake bed, which is why it was selected as the landing sight for the Curiosity rover in 2012.

*Illustrates showing the origin of some deposits in the Eridania basin of southern Mars resulting from seafloor hydrothermal activity more than 3 billion years ago. Credit: NASA*

Since Mars had both surface water and volcanic activity during this time, it would have also experienced hydrothermal activity. This occurs when volcanic vents open into standing bodies of water, filling them with hydrated minerals and heat. On Earth, which still has an active crust, evidence of past hydrothermal activity cannot be preserved. But on Mars, where the crust is solid and erosion is minimal, the evidence has been preserved.

“This site gives us a compelling story for a deep, long-lived sea and a deep-sea hydrothermal environment,” Niles said. “It is evocative of the deep-sea hydrothermal environments on Earth, similar to environments where life might be found on other worlds — life that doesn’t need a nice atmosphere or temperate surface, but just rocks, heat and water.”

Based on their study, the researchers estimate that the Eridania basin once held about 210,000 cubic km (50,000 cubic mi) of water. Not only is this nine times more water than all of the Great Lakes combined, it is as much as all the other lakes and seas on ancient Mars combined. In addition, the region also experienced lava flows that existed after the sea is believed to have disappeared.

From the CRISM’s spectrometer data, the team identified deposits of serpentine, talc and carbonate. Combined with the shape and texture of the bedrock layers, they concluded that the sea floor was open to volcanic fissures. Beyond indicating that this region could have once hosted life, this study also adds to the diversity of the wet environments which are once believed to have existed on Mars.

A scale model compares the volume of water contained in lakes and seas on the Earth and Mars to the estimated volume of water contained in an ancient Eridania sea. Credit: JJoseph R. Michalski (et al.)/Nature Communications

Between evidence of ancient lakes, rivers, groundwater, deltas, seas, and volcanic eruptions beneath ice, scientists now have evidence of volcanic activity that occurred beneath a standing body of water (aka. hot springs) on Mars. This also represents a new category for astrobiological research, and a possible destination for future missions to the Martian surface.

The study of hydrothermal activity is also significant as far as finding sources of extra-terrestrial, like on the moons of Europa, Enceladus, Titan, and elsewhere. In the future, robotic missions are expected to travel to these worlds in order to peak beneath their icy surfaces, investigate their plumes, or venture into their seas (in Titan’s case) to look for the telltale traces of basic life forms.

The study also has significance beyond Mars and could aid in the study of how life began here on Earth. At present, the earliest evidence of terrestrial life comes from seafloor deposits that are similar in origin and age to those found in the Eridania basin. But since the geological record of this period on Earth is poorly preserved, it has been impossible to determine exactly what conditions were like at this time.

Given Mars’ similarities with Earth, and the fact that its geological record has been well-preserved over the past 3 billion years, scientists can look to mineral deposits and other evidence to gauge how natural processes here on Earth allowed for life to form and evolve over time. It could also advance our understanding of how all the terrestrial planets of the Solar System evolved over billions of years.

Further Reading: NASA

September 25, 2017November 9, 2017 by Susie Murph

Astronomy Cast Ep. 458: The Science of Cassini

And now Cassini’s gone. Smashed up in the atmosphere of Saturn. But planetary scientists are going to be picking through all those pictures and data for decades. Let’s look back at some of the science gathered up by Cassini so far, and we can still learn from this epic journey.

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September 18, 2017November 9, 2017 by Susie Murph

Astronomy Cast Ep. 457: Why Did Cassini Have To Die? In Memoriam

It’s time to say goodbye to an old friend, NASA’s Cassini spacecraft, which has been orbiting within the Saturnian system since 2004. But why does a seemingly healthy spacecraft and mission need to come to an end? Today we look back at the mission, some of the amazing discoveries, and why its finale was necessary.

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September 12, 2017September 13, 2017 by Matt Williams

Cassini Conducts a Final Flyby of Titan Before Crashing into Saturn

Illustration of the Cassini probe in orbit of Saturn. The probe will descend into Saturn's atmosphere on Sept. 15th, 2017. Credit: NASA/JPL-Caltech

When the Cassini spacecraft arrived around Saturn on July 1st, 2004, it became the fourth space probe to visit the system. But unlike the Pioneer 11 and Voyager 1 and 2 probes, the Cassini mission was the first to establish orbit around the planet for the sake of conducting long-term research. Since that time, the spacecraft and its accompanying probe – the Huygens lander – have revealed a startling amount about this system.

On Friday, September 15th, the Cassini mission will official end as the spacecraft descends into Saturn’s atmosphere. In part of this final maneuver, Cassini recently conducted one last distant flyby of Titan. This flyby is being referred to informally as “the goodbye kiss” by mission engineers, since it is providing the gravitational push necessary to send the spacecraft into Saturn’s upper atmosphere, where it will burn up.

In the course of this flyby, the spacecraft made its closest approach to Titan on Tuesday, September 12th, at 12:04 p.m. PDT (3:04 p.m. EDT), passing within 119,049 kilometers (73,974 mi) of the moon’s surface. The maneuver was designed to slow the probe down and lower the altitude of its orbit around the planet, which will cause it to descend into Saturn’s atmosphere in a few day’s time.

*Artist’s conception of Cassini winging by Saturn’s moon Titan (right) with the planet in the background. Credit: NASA/JPL-Caltech*

The flyby also served as an opportunity to collect some final pictures and data on Saturn’s largest moon, which has been a major focal point for much of the Cassini-Huygens mission. These will all be transmitted back to Earth at 18:19 PDT (21:19 EDT) when the spacecraft makes contact, and navigators will use this opportunity to confirm that Cassini is on course for its final dive.

All told, the spacecraft made hundreds of passes over Titan during its 13-year mission. These included a total of 127 precisely targeted encounters at close and far range (like this latest flyby). As Cassini Project Manager Earl Maize, from NASA’s Jet Propulsion Laboratory, said in a NASA press statement:

“Cassini has been in a long-term relationship with Titan, with a new rendezvous nearly every month for more than a decade. This final encounter is something of a bittersweet goodbye, but as it has done throughout the mission, Titan’s gravity is once again sending Cassini where we need it to go.”

In the course of making its many flybys, the Cassini spacecraft revealed a great deal about the composition of Titan’s atmosphere, its methane cycle (similar to Earth’s hydrological cycle) and the kinds of weather it experiences in its polar regions. The probe also provided high-resolution radar images of Titan’s surface, which included topography and images of its northern methane lakes.

*Artist depiction of Huygens lander touching down on the surface of Saturn’s largest moon Titan. Credit: ESA*

Cassini’s first flyby of Titan took place on July 2nd, 2004 – a day after the spacecraft’s orbital insertion – where it approached to within 339,000 km (211,000 mi) of the moon’s surface. On December 25th, 2004, Cassini released the Huygens lander into the planet’s atmosphere. The probe touched down on January 14th, 2005, taking hundreds of pictures of the moon’s surface in the process.

In November of 2016, the spacecraft began the Grand Finale phase of its mission, where it would make 22 orbits between Saturn and its rings. This phase began with a flyby of Titan that took it to the gateway of Saturn’s’ F-ring, the outermost and perhaps most active ring around Saturn. This was followed by a final close flyby of Titan on April 22nd, 2017, taking it to within 979 km (608 mi) of the moon’s surface.

Throughout its mission, Cassini also revealed some significant things about Saturn’s atmosphere, its hexagonal storms, its ring system, and its extensive system of moons. It even revealed previously-undiscovered moons, such as Methone, Pallene and Polydeuces. Last, but certainly not least, it conducted studies of Saturn’s moon Enceladus that revealed evidence of a interior ocean and plume activity around its southern polar region.

These discoveries are part of the reason why the probe will end its mission by plunging into Saturn’s atmosphere, about two days and 16 hours from now. This will cause the probe to burn up, thus preventing contamination of moons like Titan and Enceladus, where microbial life could possibly exist. Finding evidence of this life will be the main focus of future missions to the Saturn system, which are likely to launch in the next decade.

So long and best wishes, Cassini! You taught so much in the past decade and we hope to follow up on it very soon. We’ll all miss you when you go!

Further Reading: NASA

August 25, 2017 by Matt Williams

Dragonfly Proposed to NASA as Daring New Frontiers Mission to Titan

Artist's concept of the dragonfly being deployed to Titan and commencing its exploration mission. Credit: Dragonfly would land on the surface of Saturn's moon Titan and then could fly from point to point on the moon's surface and settle to investigate and recharge. Credit: APL/Michael Carroll

In late 1970s and early 80s, scientists got their first detailed look at Saturn’s largest moon Titan. Thanks to the Pioneer 11 probe, which was then followed by the Voyager 1 and 2 missions, the people of Earth were treated to images and readings of this mysterious moon. What these revealed was a cold satellite that nevertheless had a dense, nitrogen-rich atmosphere.

Thanks to the Cassini-Huygens mission, which reached Titan in July of 2004 and will be ending its mission on September 15th, the mysteries of this moon have only deepened. Hence why NASA hopes to send more missions there in the near future, like the Dragonfly concept. This craft is the work of the John Hopkins University Applied Physics Laboratory (JHUAPL), which they just submitted an official proposal for.

Essentially, Dragonfly would be a New Frontiers-class mission that would use a dual-quadcopter setup to get around. This would enable vertical-takeoff and landing (VTOL), ensuring that the vehicle would be capable of exploring Titan’s atmosphere and conducting science on the surface. And of course, it would also investigate Titan’s methane lakes to see what kind of chemistry is taking place within them.

The goal of all this would be to shed light on Titan’s mysterious environment, which not only has a methane cycle similar to Earth’s own water cycle, but is rich in prebiotic and organic chemistry. In short, Titan is an “ocean world” of our Solar System – along with Jupiter’s moons Europa and Ganymede, and Saturn’s moon of Enceladus – that could contain all the ingredients necessary for life.

What’s more, previous studies have shown that the moon is covered in rich deposits of organic material that are undergoing chemical processes, ones that might be similar to those that took place on Earth billions of years ago. Because of this, scientists have come to view Titan as a sort of planetary laboratory, where the chemical reactions that may have led to life on Earth could be studied.

As Elizabeth Turtle, a planetary scientist at JHUAPL and the principal investigator for the Dragonfly mission, told Universe Today via email:

“Titan offers abundant complex organics on the surface of a water-ice-dominated ocean world, making it an ideal destination to study prebiotic chemistry and to document the habitability of an extraterrestrial environment. Because Titan’s atmosphere obscures the surface at many wavelengths, we have limited information about the materials that make up the surface and how they’re processed. By making detailed surface composition measurements in multiple locations, Dragonfly would reveal what the surface is made of and how far prebiotic chemistry has progressed in environments that provide known key ingredients for life, identifying the chemical building blocks available and processes at work to produce biologically relevant compounds.”

In addition, Dragonfly would also use remote-sensing observations to characterize the geology of landing sites. In addition to providing context for the samples, it would also allow for seismic studies to determine the structure of the Titan and the presence of subsurface activity. Last, but not least, Dragonfly would use meteorology sensors and remote-sensing instruments to gather information on the planet’s atmospheric and surface conditions.

*The Aerial Vehicle for In-situ and Airborne Titan Reconnaissance (AVIATR) is another concept for an aerial explorer for Titan. Credit: Mike Malaska*

While multiple proposals have been made for a robotic explorer mission of Titan, most of these have taken the form of either an aerial platforms or a combination balloon and a lander. The Aerial Vehicle for In-situ and Airborne Titan Reconnaissance (AVIATR), a proposal made in the past by Jason Barnes and a team of researchers from the University of Idaho, is an example of the former.

In the latter category, you have concepts like the Titan Saturn System Mission (TSSM), a concept that was being jointly-developed by the European Space Agency (ESA) and NASA. An Outer Planets Flagship Mission concept, the design of the TSSM consisted of three elements – a NASA orbiter, an ESA-designed lander to explore Titan’s lakes, and an ESA-designed Montgolfiere balloon to explore its atmosphere.

What separates Dragonfly from these and other concepts is its ability to conduct aerial and ground-based studies with a single platform. As Dr. Turtle explained:

“Dragonfly would be an in situ mission to perform detailed measurements of Titan’s surface composition and conditions to understand the habitability of this unique organic-rich ocean world. We proposed a rotorcraft to take advantage of Titan’s dense, calm atmosphere and low gravity (which make flight easier on Titan than it is on Earth) to convey a capable suite of instruments from place to place — 10s to 100s of kilometers apart — to make measurements in different geologic settings. Unlike other aerial concepts that have been considered for Titan exploration (of which there have been several), Dragonfly would spend most of its time on the surface performing measurements, before flying to another site.”

Dragonfly‘s suite of instruments would include mass spectrometers to study the composition of the surface and atmosphere; gamma-ray spectrometers, which would measure the composition of the subsurface (i.e. looking for evidence of an interior ocean); meteorology and geophysics sensors, which would measure wind, atmospheric pressure, temperature and seismic activity; and a camera suite to snap pictures of the surface.

*Artist’s concept of the Titan Aerial Daughter quadcopter and its “Mothership” balloon. Credit: NASA/STMD*

Given Titan’s dense atmosphere, solar cells would not be an effective option for a robotic mission. As such, the Dragonfly would rely on a Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) for power, similar to what the Curiosity rover uses. While robotic missions that rely on nuclear power sources are not exactly cheap, they do enable missions that can last for years at a time and conduct invaluable research (as Curiosity has shown).

As Peter Bedini – the Program Manager at the JHUAPL Space Department and Dragonfly’s project manager – explained, this would allow for a long-term mission with significant returns:

“We could take a lander, put it on Titan, take these four measurements at one place, and significantly increase our understanding of Titan and similar moons. However, we can multiply the value of the mission if we add aerial mobility, which would enable us to access a variety of geologic settings, maximizing the science return and lowering mission risk by going over or around obstacles.”

In the end, a mission like Dragonfly would be able to investigate how far prebiotic chemistry has progressed on Titan. These types of experiments, where organic building blocks are combined and exposed to energy to see if life emerges, cannot be performed in a laboratory (mainly because of the timescales involved). As such, scientists hope to see how far things have progressed on Titan’s surface, where prebiotic conditions have existed for eons.

In addition, scientists will also be looking for chemical signatures that indicate the presence of water and/or hydrocarbon-based life. In the past, it has been speculated that life could exist within Titan’s interior, and that exotic methanogenic lifeforms could even exist on its surface. Finding evidence of such life would challenge our notions of where life can emerge, and greatly enhance the search for life within the Solar System and beyond.

As Dr. Turtle indicated, mission selection will be coming soon, and whether or not the Dragonfly mission will be sent to Titan should be decided in just a few years time:

“Later this fall, NASA will select a few of the proposed New Frontiers missions for further work in Phase A Concept Studies” she said. “Those studies would run for most of 2018, followed by another round of review. And the final selection of a flight mission would be in mid-2019… Missions proposed to this round of the New Frontiers Program would be scheduled to launch before the end of 2025.”

And be sure to check out this video of a possible Dragonfly mission, courtesy of the JHUAPL:

Further Reading: JHU Hub

July 31, 2017July 31, 2017 by Matt Williams

NASA Detects More Chemicals on Titan that are Essential to Life

Saturn’s largest moon Titan may be the most fascinating piece of real-estate in the Solar System right now. Not surprising, given the fact that the moon’s dense atmosphere, rich organic environment and prebiotic chemistry are thought to be similar to Earth’s primordial atmosphere. As such, scientists believe that the moon could act as a sort of laboratory for studying the processes whereby chemical elements become the building blocks for life.

These studies have already led to a wealth of information, which included the recent discovery of “carbon chain anions” – which are thought to be building blocks for more complex molecules. And now, thanks to data from the the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, a team of NASA researchers have detected the presence of acrylonitrile, another chemical elements that could be the basis for life on that moon.

The study that details their findings – titled “ALMA detection and astrobiological potential of vinyl cyanide on Titan” – was published in the July 28th issue of the journal Science Advances. In it, the team explains how data from the ALMA array indicated that large quantities of acrylonitrile (C₂H₃CN) exist on Titan – most likely within the moon’s stratosphere.

As Maureen Palmer, a researcher with the Goddard Center for Astrobiology and the lead author on the paper, indicated in a NASA press release: “We found convincing evidence that acrylonitrile is present in Titan’s atmosphere, and we think a significant supply of this raw material reaches the surface.”

Also known as vinyl cyanide, acrylonitrile is used here on Earth in the manufacture of plastics. In the past, it has been speculated that this compound could be present in Titan’s atmosphere. However, it was only recently that scientists became aware of the possibility that it be the basis for living creatures within Titan’s rich organic environment – with its steady supply of carbon, hydrogen, and nitrogen.

This is based on a study that was conducted in 2015, where a team of Cornell scientists sought to determine if organic cells could form in Titan’s harsh environment. Given that the moon experiences average surface temperatures of -179 °C (-290 °F) and the atmosphere is predominantly nitrogen and hydrocarbons, lipid bilayer membranes (which are the foundation of life on Earth) could not survive there.

However, after conducting molecular simulations, the team determined that small organic nitrogen compounds would be capable of forming a sheet of material similar to a cell membrane. They also determined that these sheets could form hollow, microscopic spheres that they dubbed “azotosomes”, and that the best chemical candidate for this sheets would be acrylonitrile.

*Artist concept of Methane-Ethane lakes on Titan (Credit: Copyright 2008 Karl Kofoed). Click for larger version.*

Such a material would be capable of surviving in liquid methane and at extremely cold temperatures, and would therefore be the most likely basis for organic life on Titan. As Michael Mumma, the director of the Goddard Center for Astrobiology, explained:

“The ability to form a stable membrane to separate the internal environment from the external one is important because it provides a means to contain chemicals long enough to allow them to interact. If membrane-like structures could be formed by vinyl cyanide, it would be an important step on the pathway to life on Saturn’s moon Titan.”

For the sake of their study, the Goddard team combined 11 high-resolution data sets from ALMA, which they retrieved from an archive of observations that were used to calibrate the array. From the data, Palmer and her team determined that acrylonitrile is relatively abundant in Titan’s atmosphere, reaching concentrations of up to 2.8 parts per billion. They also determined that it would be most common in Titan’s upper atmosphere.

It is here that carbon, hydrogen and nitrogen could chemically bond from exposure to sunlight and energetic particles from Saturn’s magnetic field. Eventually, the acrylonitrile would make its way down through the cold atmosphere and condense to form rain droplets that would fall to the surface. The team also estimated how much of this material would accumulate in Ligeia Mare – Titan’s second-largest methane lake – over time.

Finally, they calculated that within every cubic centimeter (cm³) of its volume, Ligeia Mare could form as many as 10,000,000 azotosomes. That roughly ten times the amount of bacteria that exists in the waters along Earth’s coastal regions. As Martin Cordiner, one of the senior authors on the paper, indicated, these findings are certainly encouraging when it comes to the search for extra-terrestrial life in our Solar System.

“The detection of this elusive, astrobiologically relevant chemical is exciting for scientists who are eager to determine if life could develop on icy worlds such as Titan,” he said. “This finding adds an important piece to our understanding of the chemical complexity of the solar system.”

Granted, the study and the basis for its conclusions are quite speculative. But they do show that within certain established parameters, life could exist within our Solar System well-beyond the limits of our Sun’s “habitable zone”. This study could also have implications in the hunt for life in extrasolar systems. If scientists can say definitively that life does not need warmer temperatures and liquid water to exist, it opens up immense possibilities.

In the coming decades, several missions are expected to go to Titan, ranging from submarines that will explore its methane lakes to drones and aerial platforms that will study its atmosphere and surface. Already, it is expected that they will obtain valuable information about the formation of the Saturn system. But to also discover entirely new forms of life? That would truly be Earth-shattering!

Further Reading: NASA, Science Advances

July 27, 2017 by Matt Williams

Cassini Finds that Titan is Building the Chemicals that Might Have Led to Life on Earth

Titan, Saturn’s largest moon, has been a source of mystery ever since scientists began studying it over a century ago. These mysteries have only deepened with the arrival of the Cassini-Huygens mission in the system back in 2004. In addition to finding evidence of a methane cycle, prebiotic conditions and organic chemistry, the Cassini-Huygens mission has also discovered that Titan may have the ingredient that help give rise to life.

Such is the argument made in a recent study by an international team of scientists. After examining data obtained by the Cassini space probe, they identified a negatively charged species of molecule in Titan’s atmosphere. Known as “carbon chain anions”, these molecules are thought to be building blocks for more complex molecules, which could played a key role in the emergence of life of Earth.

The study, titled “Carbon Chain Anions and the Growth of Complex Organic Molecules in Titan’s Ionosphere“, recently appeared in The Astrophysical Journal Letters. The team included researchers from University College in London, the University of Grenoble, Uppsalla University, UCL/Birkbeck, the University of Colorado, the Swedish Institute of Space Physics, the Southwest Research Institute (SwRI), and NASA’s Goddard Space Flight Center.

*Diagram of the internal structure of Titan according to the fully differentiated dense-ocean model. Credit: Wikipedia Commons/Kelvinsong*

As they indicate in their study, these molecules were detected by the Cassini P lasma Spectrometer (CAPS) as the probe flew through Titan’s upper atmosphere at an distance of 950 – 1300 km (590 – 808 mi) from the surface. They also show how the presence of these molecules was rather unexpected, and represent a considerable challenge to current theories about how Titan’s atmosphere works.

For some time, scientists have understood that within Titan’s ionosphere, nitrogen, carbon and hydrogen are subjected to sunlight and energetic particles from Saturn’s magnetosphere. This exposure drives a process where these elements are transformed into more complex prebiotic compounds, which then drift down towards the lower atmosphere and form a thick haze of organic aerosols that are thought to eventually reach the surface.

This has been the subject of much interest, since the process through which simple molecules form complex organic ones has remained something of a mystery to scientists. This could be coming to an end thanks to the detection of carbon chain anions, though their discovery was altogether unexpected. Since these molecules are highly reactive, they are not expected to last long in Titan’s atmosphere before combining with other materials.

However, the data showed that the carbon chains became depleted closer to the moon, while precursors to larger aerosol molecules underwent rapid growth. This suggests that there is a close relationship between the two, with the chains ‘seeding’ the larger molecules. Already, scientists have held that these molecules were an important part of the process that allowed for life to form on Earth, billions of years ago.

*A halo of light surrounds Saturn’s moon Titan in this backlit picture, showing its atmosphere. Credit: NASA/JPL/Space Science Institute*

However, their discovery on Titan could be an indication of how life begins to emerge throughout the Universe. As Dr. Ravi Desai, University College London and the lead author of the study, explained in an ESA press release:

“We have made the first unambiguous identification of carbon chain anions in a planet-like atmosphere, which we believe are a vital stepping-stone in the production line of growing bigger, and more complex organic molecules, such as the moon’s large haze particles. This is a known process in the interstellar medium, but now we’ve seen it in a completely different environment, meaning it could represent a universal process for producing complex organic molecules.”

Because of its dense nitrogen and methane atmosphere and the presence of some of the most complex chemistry in the Solar System, Titan is thought by many to be similar to Earth’s early atmosphere. Billions of years ago, before the emergence of microorganisms that allowed for subsequent build-up of oxygen, it is likely that Earth had a thick atmosphere composed of nitrogen, carbon dioxide and inert gases.

Therefore, Titan is often viewed as a sort planetary laboratory, where the chemical reactions that may have led to life on Earth could be studied. However, the prospect of finding a universal pathway towards the ingredients for life has implications that go far beyond Earth. In fact, astronomers could start looking for these same molecules on exoplanets, in an attempt to determine which could give rise to life.

*This illustration shows Cassini above Saturn’s northern hemisphere prior to one of its 22 Grand Finale dives. Credit: NASA/JPL-Caltech*

Closer to home, the findings could also be significant in the search for life in our own Solar System. “The question is, could it also be happening within other nitrogen-methane atmospheres like at Pluto or Triton, or at exoplanets with similar properties?” asked Desia. And Nicolas Altobelli, the Project Scientist for the Cassini-Huygens mission, added:

“These inspiring results from Cassini show the importance of tracing the journey from small to large chemical species in order to understand how complex organic molecules are produced in an early Earth-like atmosphere. While we haven’t detected life itself, finding complex organics not just at Titan, but also in comets and throughout the interstellar medium, we are certainly coming close to finding its precursors.“

Cassini’s “Grande Finale“, the culmination of its 13-year mission around Saturn and its system of moons, is set to end on September 15th, 2017. In fact, as of the penning of this article, the mission will end in about 1 month, 18 days, 16 hours, and 10 minutes. After making its final pass between Saturn’s rings, the probe will be de-orbited into Saturn’s atmosphere to prevent contamination of the system’s moons.

However, future missions like the James Webb Space Telescope, the ESA’s PLATO mission and ground-based telescopes like ALMA are expected to make some significant exoplanet finds in the coming years. Knowing specifically what kinds of molecules are intrinsic in converting common elements into organic molecules will certainly help narrow down the search for habitable (or even inhabited) planets!

Further Reading: ESA, The Astrophysical Journal Letters