Image of Titan’s surface obtained by the European Space Agency’s Huygens probe from an approximate altitude of 10 kilometers (6.2 miles) during the probe’s slow descent to the surface on January 14, 2005. (Credit: ESA/NASA/JPL/University of Arizona)
Does Saturn’s largest moon, Titan, possess the necessary ingredients for life to exist? This is what a recent study published in Astrobiology hopes to address as a team of international researchers led by Western University investigated if Titan, with its lakes of liquid methane and ethane, could possess the necessary organic materials, such as amino acids, that could be used to produce life on the small moon. This study holds the potential to help researchers and the public better understand the geochemical and biological processes necessary for life to emerge throughout the cosmos.
Universe Today recently examined the potential for sending humans to Jupiter’s icy moon, Europa, and the planet Venus, both despite their respective harsh surface environments. While human missions to these exceptional worlds could be possible in the future, what about farther out in the solar system to a world with much less harsh surface conditions, although still inhospitable for human life? Here, we will investigate whether Saturn’s largest moon, Titan, could be a feasible location for sending humans sometime in the future. Titan lacks the searing temperatures and crushing pressures of Venus along with the harsh radiation experienced on Europa. So, should we send humans to Titan?
Explorers either have the benefit of having maps or the burden of creating them. Similarly, space explorers have been building maps as they go, using all available tools. Those tools might not always be up to the task, but at least something is better than nothing. Now, a new map of an exploration destination has emerged – a map of the river valleys of Titan.
This true-color image of Titan, taken by the Cassini spacecraft, shows the moon's thick, hazy atmosphere. Credit: NASA
Titan is a mysterious, strange place for human eyes. It’s a frigid world, with seas of liquid hydrocarbons, and a structure made up of layers of water, different kinds of ice, and a core of hydrous silicates. It may even have cryovolcanoes. Adding to the odd nature of Saturn’s largest moon is the presence of exotic crystals on the shores of its hydrocarbon lakes.
Ligeia Mare, shown in here in data obtained by NASA's Cassini spacecraft, is the second largest known body of liquid on Saturn's moon Titan. It is filled with liquid hydrocarbons, such as ethane and methane, and is one of the many seas and lakes that bejewel Titan's north polar region. Credit: NASA/JPL-Caltech/ASI/Cornell
Thanks to the Cassini mission, we have learned some truly amazing things about Saturn and its largest moon, Titan. This includes information on its dense atmosphere, its geological features, its methane lakes, methane cycle, and organic chemistry. And even though Cassini recently ended its mission by crashing into Saturn’s atmosphere, scientists are still pouring over all of the data it obtained during its 13 years in the Saturn system.
And now, using Cassini data, two teams led by researchers from Cornell University have released two new studies that reveal even more interesting things about Titan. In one, the team created a complete topographic map of Titan using Cassini’s entire data set. In the second, the team revealed that Titan’s seas have a common elevation, much like how we have a “sea level” here on Earth.
This true-color image of Titan, taken by the Cassini spacecraft, shows the moon’s thick, hazy atmosphere. Credit: NASA
In the first paper, the authors described how topographic data from multiple sources was combined to create a global map of Titan. Since only about 9% of Titan was observed with high-resolution topography (and 25-30% in lower resolution) the remainder of the moon was mapped with an interpolation algorithm. Combined with a global minimization process, this reduced errors that would arise from such things as spacecraft location.
The map revealed new features on Titan, as well as a global view of the highs and lows of the moon’s topography. For instance, the maps showed several new mountains which reach a maximum elevation of 700 meters (about 3000 ft). Using the map, scientists were also able to confirm that two locations in the equatorial regions are depressions that could be the result of ancient seas that have since dried up or cryovolcanic flows.
The map also suggests that Titan may be more oblate than previously thought, which could mean that the crust varies in thickness. The data set is available online, and the map which the team created from it is already proving its worth to the scientific community. As Professor Corlies explained in a Cornell press release:
“The main point of the work was to create a map for use by the scientific community… We’re measuring the elevation of a liquid surface on another body 10 astronomical units away from the sun to an accuracy of roughly 40 centimeters. Because we have such amazing accuracy we were able to see that between these two seas the elevation varied smoothly about 11 meters, relative to the center of mass of Titan, consistent with the expected change in the gravitational potential. We are measuring Titan’s geoid. This is the shape that the surface would take under the influence of gravity and rotation alone, which is the same shape that dominates Earth’s oceans.”
False-color mosaic of Titan’s northern lakes, made from infrared data collected by NASA’s Cassini spacecraft. Credit: NASA
Looking ahead, this map will play an important role when it comes tr scientists seeking to model Titan’s climate, study its shape and gravity, and its surface morphology. In addition, it will be especially helpful for those looking to test interior models of Titan, which is fundamental to determining if the moon could harbor life. Much like Europa and Enceladus, it is believed that Titan has a liquid water ocean and hydrothermal vents at its core-mantle boundary.
The second study, which also employed the new topographical map, was based on Cassini radar data that was obtained up to just a few months before the spacecraft burned up in Saturn’s atmosphere. Using this data, Assistant Professor Hayes and his team determined that Titan’s seas follow a constant elevation relative to Titan’s gravitational pull. Basically, they found that Titan has a sea level, much like Earth. As Hayes explained:
“We’re measuring the elevation of a liquid surface on another body 10 astronomical units away from the sun to an accuracy of roughly 40 centimeters. Because we have such amazing accuracy we were able to see that between these two seas the elevation varied smoothly about 11 meters, relative to the center of mass of Titan, consistent with the expected change in the gravitational potential. We are measuring Titan’s geoid. This is the shape that the surface would take under the influence of gravity and rotation alone, which is the same shape that dominates Earth’s oceans.”
This common elevation is important because liquid bodies on Titan appear to be connected by something resembling an aquifer system. Much like how water flows underground through porous rock and gravel on Earth, hydrocarbons do the same thing under Titan’s icy surface. This ensures that there is transference between large bodies of water, and that they share a common sea level.
Artist concept of Cassini’s last moments at Saturn. Credit: NASA/JPL.
“We don’t see any empty lakes that are below the local filled lakes because, if they did go below that level, they would be filled themselves,” said Hayes. “This suggests that there’s flow in the subsurface and that they are communicating with each other. It’s also telling us that there is liquid hydrocarbon stored on the subsurface of Titan.”
Meanwhile, smaller lakes on Titan appear at elevations several hundred meters above Titan’s sea level. This is not dissimilar to what happens on Earth, where large lakes are often found at higher elevations. These are known as “Alpine Lakes”, and some well-known examples include Lake Titicaca in the Andes, Lakes Geneva in the Alps, and Paradise Lake in the Rockies.
Last, but not least, the study also revealed the vast majority of Titan’s lakes are found within sharp-edged depressions that are surrounded by high ridges, some of which are hundreds of meters high. Here too, there is a resemblance to features on Earth – such as the Florida Everglades – where underlying material dissolves and causes the surface to collapse, forming holes in the ground.
The shape of these lakes indicate that they may be expanding at a constant rate, a process known as uniform scarp retreat. In fact, the largest lake in the south – Ontario Lacus – resembles a series of smaller empty lakes that have coalesced to form a single feature. This process is apparently due to seasonal change, where autumn in the southern hemisphere leads to more evaporation.
While the Cassini mission is no longer exploring the Saturn system, the data it accumulated during its multi-year mission is still bearing fruit. Between these latest studies, and the many more that will follow, scientists are likely to reveal a great deal more about this mysterious moon and the forces that shape it!
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.
Image of Titan’s atmosphere, snapped by the Cassini spacecraft. Credit: NASA/JPL/Space Science Institute
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)!
A new study has revealed that Titan's methane lakes could be calm enough for future missions to land there. Credit: bisbos.com
Ever since the Cassini orbiter and the Huygens lander provided us with the first detailed glimpse of Saturn’s moon Titan, scientists have been eager to mount new missions to this mysterious moon. Between its hydrocarbon lakes, its surface dunes, its incredibly dense atmosphere, and the possibility of it having an interior ocean, there is no shortage of things that are worthy of research.
The only question is, what form would this mission take (i.e. aerial drone, submarine, balloon, lander) and where should it set down? According to a new study led by the University of Texas at Austin, Titan’s methane lakes are very calm and do not appear to experience high waves. As such, these seas may be the ideal place for future missions to set down on the moon.
Titan’s three largest lakes and their surrounding areas as seen by the Cassini RADAR instrument. The researchers used the instrument to study waves on the lake surfaces. Credit: Cyril Grima/ The University of Texas at Austin
As Grima explained in a University of Texas press release, this research also shed light on the meteorological activity on Titan:
“There’s a lot of interest in one day sending probes to the lakes, and when that’s done, you want to have a safe landing, and you don’t want a lot of wind. Our study shows that because the waves aren’t very high, the winds are likely low.”
Towards this end, Grima and his colleagues examined radar data obtained by the Cassini mission during Titan’s early summer season. This consisted of measurements of Titan’s northern lakes, which included Ontario Lacus, Ligeia Mare, Punga Mare, and Kraken Mare. The largest of the three, Kraken Mars, is estimated to be larger than the Caspian Sea – i.e. 4,000,000 km² (1,544,409 mi²) vs 3,626,000 km2 (1,400,000 mi²).
With the help of the Cassini RADAR Team and researchers from Cornell University, the Johns Hopkins University Applied Physics Laboratory (JHUAPL), NASA’s Jet Propulsion Laboratory (JPL) and elsewhere, the team applied a technique known as radar statistical reconnaissance. Developed by Grima, this technique relies on radar data to measure the roughness of surfaces in minute detail.
This technique has also been used to measure snow density and the surface roughness of ice in Antarctica and the Arctic. Similarly, NASA has used the technique for the sake of selecting a landing site on Mars for their Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (Insight) lander, which is scheduled to launch next year.
The left image shows a mosaic of images of Titan taken by the Cassini spacecraft in near infrared light. Titan’s polar seas are visible as sunlight glints off of them. The right image is a radar image of Kraken Mare. Credit: NASA Jet Propulsion Laboratory.
From this, Grima and his colleagues determined that waves on these lakes are quite small, reaching only 1 cm in height and 20 cm in length. These findings indicate that these lakes would be a serene enough environment that future probes could make soft landings on them and then begin the task of exploring the surface of the moon. As with all bodies, waves on Titan could be wind-driven, triggered by tidal flows, or the result of rain or debris.
As a result, these results are calling into question what scientists think about seasonal change on Titan. In the past, it was believed that summer on Titan was the beginning of moon’s windy season. But if this were the case, the results would have indicated higher waves (the result of higher winds). As Alex Hayes, an assistant professor of astronomy at Cornell University and a co-author on the study, explained:
“Cyril’s work is an independent measure of sea roughness and helps to constrain the size and nature of any wind waves. From the results, it looks like we are right near the threshold for wave generation, where patches of the sea are smooth and patches are rough.”
These results are also exciting for scientists who are hoping to plot future missions to Titan, especially by those who are hoping to see a robotic submarine sent to Titan’s to investigate its lakes for possible signs of life. Other mission concepts involve exploring Titan’s interior ocean, its surface, and its atmosphere for the sake of learning more about the moon’s environment, its organic-rich environment and probiotic chemistry.
And who knows? Maybe, just maybe, these missions will find that life in our Solar System is more exotic than we give it credit before, going beyond the carbon-based life that we are familiar with to include the methanogenic.
The appearing and disappearing feature observed in Titan's Lakes was dubbed "Magic Island". Image: NASA/JPL-Caltech/ASI/Cornell
Saturn’s largest Moon, Titan, is the only other world in our Solar System that has stable liquid on its surface. That alone, and the fact that the liquid is composed of methane, ethane, and nitrogen, makes it an object of fascination. The bright spot features that Cassini observed in the methane seas that dot the polar regions only deepen the fascination.
A new paper published in Nature Astronomy digs deeper into a phenomenon in Titan’s seas that has been puzzling scientists. In 2013, Cassini noticed a feature that wasn’t there on previous fly-bys of the same region. In subsequent images, the feature had disappeared again. What could it be?
One explanation is that the feature could be a disappearing island, rising and falling in the liquid. This idea took hold, but was only an initial guess. Adding to the mystery was the doubling in size of these potential islands. Others speculated that they could be waves, the first waves observed anywhere other than on Earth. Binding all of these together was the idea that the appearance and disappearance could be caused by seasonal changes on the moon.
Titan’s dense, hydrocarbon rich atmosphere remains a focal point of scientific research. Credit: NASA
Now, scientists at NASA’s Jet Propulsion Laboratory (JPL) think they know what’s behind these so-called ‘disappearing islands,’ and it seems like they are related to seasonal changes.
The study was led by Michael Malaska of JPL. The researchers simulated the frigid conditions on Titan, where the temperature is -179.2 Celsius. At that temperature, some interesting things happen to the nitrogen in Titan’s atmosphere.
On Titan, it rains. But the rain is composed of extremely cold methane. As that methane falls to the surface, it absorbs significant amounts of nitrogen from the atmosphere. The rain hits Titan’s surface and collects in the lakes on the moon’s polar regions.
The researchers manipulated the conditions in their experiments to mirror the changes that occur on Titan. They changed the temperature, the pressure, and the methane/ethane composition. As they did so, they found that nitrogen bubbled out of solution.
“Our experiments showed that when methane-rich liquids mix with ethane-rich ones — for example from a heavy rain, or when runoff from a methane river mixes into an ethane-rich lake — the nitrogen is less able to stay in solution,” said Michael Malaska of JPL. This release of nitrogen is called exsolution. It can occur when the seasons change on Titan, and the seas of methane and ethane experience a slight warming.
“Thanks to this work on nitrogen’s solubility, we’re now confident that bubbles could indeed form in the seas, and in fact may be more abundant than we’d expected,” said Jason Hofgartner of JPL, a co-author of the study who also works on Cassini’s radar team. These nitrogen bubbles would be very reflective, which explains why Cassini was able to see them.
The first-ever images of the surface of a new moon or planet are always exciting. The Huygens probe was launched from Cassini to the surface of Titan, but was not able investigate the lakes and seas on the surface. Image Credit: ESA/NASA/JPL/University of Arizona
The seas on Titan may be what’s called a prebiotic environment, where chemical conditions are hospitable to the appearance of life. Some think that the seas may already be home to life, though there’s no evidence of this, and Cassini wasn’t equipped to investigate that premise. Some experiments have shown that an atmosphere like Titan’s could generate complex molecules, and even the building blocks of life.
NASA and others have talked about different ways to explore Titan, including balloons, a drone, splashdown landers, and even a submarine. The submarine idea even received a NASA grant in 2015, to develop the idea further.
So, mystery solved, probably. Titan’s bright spots are neither islands nor waves, but bubbles.
Cassini’s mission will end soon, and it’ll be quite some time before Titan can be investigated further. The question of whether Titan’s seas are hospitable to the formation of life, or whether there may already be life there, will have to wait. What role the nitrogen bubbles play in Titan’s life question will also have to wait.
The Aerial Vehicle for In-situ and Airborne Titan Reconnaissance (AVIATR) concept for an aerial explorer for Titan. Credit: Mike Malaska
Last week, from Monday Feb. 27th to Wednesday March 1st, NASA hosted the “Planetary Science Vision 2050 Workshop” at their headquarters in Washington, DC. During the course of the many presentations, speeches and addresses that made up the workshop, NASA and its affiliates shared their many proposals for the future of Solar System exploration.
A very popular theme during the workshop was the exploration of Titan. In addition to being the only other body in the Solar System with a nitrogen-rich atmosphere and visible liquid on its surface, it also has an environment rich in organic chemistry. For this reason, a team led by Michael Pauken (from NASA’s Jet Propulsion Laboratory) held a presentation detailing the many ways it can be explored using aerial vehicles.
The presentation, which was titled “Science at a Variety of Scientific Regions at Titan using Aerial Platforms“, was also chaired by members of the aerospace industry – such as AeroVironment and Global Aerospace from Monrovia, California, and Thin Red Line Aerospace from Chilliwack, BC. Together, they reviewed the various aerial platform concepts that have been proposed for Titan since 2004.
Artist depiction of the ESA’s Huygens lander setting down on Titan, which took place on January 14th. Credit: ESA
While the concept of exploring Titan with aerial drones and balloons dates back to the 1970s and 80s, 2004 was especially important since it was at this time that the Huygens lander conducted the first exploration of the moon’s surface. Since that time, many interesting and feasible proposals for aerial platforms have been made. As Dr. Pauken told Universe Today via email:
“The Cassini-Huygens mission revealed a lot about Titan we didn’t know before and that has also raised a lot more questions. It helped us determine that imaging the surface is possible below 40-km altitude so it’s exciting to know we could take aerial photos of Titan and send them back home.”
These concepts can be divided into two categories, which are Lighter-Than-Air (LTA) craft and Heavier-Than-Air (HTA) craft. And as Pauken explained, these are both well-suited when it comes to exploring a moon like Titan, which has an atmosphere that is actually denser than Earth’s – 146.7 kPa at the surface compared to 101 kPa at sea level on Earth – but only 0.14 times the gravity (similar to the Moon).
“The density of Titan’s atmosphere is higher than Earth’s so it is excellent for flying lighter-than-air vehicles like a balloon,” he said. “Titan’s low gravity is a benefit for heavier-than-air vehicles like helicopters or airplanes since they will ‘weigh’ less than they would on Earth.”
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. Credit: NASA/JPL-Caltech/Space Science Institute
“The Lighter-than-air LTA concepts are buoyant and don’t need any energy to stay aloft, so more energy can be directed towards science instruments and communications. The Heavier-than-air concepts have to consume power to stay in the air which takes away from science and telecom. But HTA can be directed to targets more quickly and accurately the LTA vehicles which mostly drift with the winds.”
TSSM Montgolfiere Balloon:
Plans for using a Montgolfiere balloon to explore Titan go back to 2008, when NASA and the ESA jointly developed the Titan Saturn System Mission (TSSM) concept. A Flagship Mission concept, the TSSM would consist of three elements including a NASA orbiter and two ESA-designed in-situ elements – a lander to explore Titan’s lakes and a Montgolfiere balloon to explore its atmosphere.
The orbiter would rely on a Radioisotopic Power System (RPS) and Solar Electric Propulsion (SEP) to reach the Saturn system. And on its way to Titan, it would be responsible for examining Saturn’s magnetosphere, flying through the plumes of Enceladus to analyze it for biological markers, and taking images of Enceladus’ “Tiger Stripes” in the southern polar region.
Artist’s concept of a Mongolfiere balloon and a deployable lander at Titan. Credit: NASA
Once the orbiter had achieved orbital insertion with Saturn, it would release the Montgolfiere during its first Titan flyby. Attitude control for the balloon would be provided by heating the ambient gas with RPS waste heat. The prime mission would last a total of about 4 years, comprised of a two-year Saturn tour, a 2-month Titan aero-sampling phase, and a 20-month Titan orbiting phase.
Of the benefits to this concept, the most obvious is the fact that a Montgolfiere vehicle powered by RPS could operate within Titan’s atmosphere for many years and would be able to change altitude with only minimal energy use. At the time, the TSSM concept was in competition with mission proposals for the moons of Europa and Ganymede.
In February of 2009, both the TSSM and the the Europa Jupiter System Mission (EJSM) concept were chosen to move forward with development, but the EJSM was given first priority. This mission was renamed the Europa Clipper, and is slated for launch in 2020 (and arriving at Europa by 2026).
Titan Helium Balloon:
Subsequent research on Montgolfiere balloons revealed that years of service and minimal energy expenditure could also be achieved in a much more compact balloon design. By combining an enveloped-design with helium, such a platform could operate in the skies of Titan for four times as long as balloons here on Earth, thanks to a much slower rate of diffusion.
Artist’s concept of the Mechanical Compression Altitude Control (MCAC) balloon, which is comprised of a number of segments that are compressed by shortening a tether that runs down the axis of the balloon. Credit: Thin Red Line Aerospace.
Altitude control would also be possible with very modest amounts of energy, which could be provided either through pump or mechanical compression. Thus, with an RPS providing power, the platform could be expected to last longer that comparable balloon designs. This envelope-helium balloon could also be paired with a glider to create a lighter-than-air vehicle capable of lateral motion as well.
Examples of the this include the Titan Winged Aerobot (TWA, shown below), which was investigated as part of NASA’s Phase One 2016 Small-Business Innovation Research (SBIR) program. Developed by the Global Aerospace Corporation, in collaboration with Northrop Grumman, the TWA is a hybrid entry vehicle, balloon, and maneuverable glider with 3-D directional control that could satisfy many science objectives.
Like the Mongtolfiere concept, it would rely on minimal power provided by a single RPS. Its unique buoyancy system would also allow it to descend and ascend without the need for propulsion systems or control surfaces. One drawback is the fact that it cannot land on the moon’s surface to conduct research and then take off again. However, the design does allow for low-altitude flight, which would allow for the delivery of probes to the surface.
Other concepts that have been developed in recent years include heavier-than-air aircraft, which center around the development of fixed-wing vehicles and rotorcraft.
Concept for a Titan Winged Aerobot, a hybrid balloon glider that does not require significant power either to stay aloft or to achieve lateral motion. Credit: Global Aerospace Corp/Northrup Grumman
Fixed Wing Vehicles:
Concepts for fixed-wing aircraft have also been proposed in the past for a mission to Titan. A notable example of this is the Aerial Vehicle for In-situ and Airborne Titan Reconnaissance (AVIATR), an unmanned aerial vehicle (UAV) that was proposed by Jason Barnes and Lawrence Lemke in 2011 (of the University of Idaho and Central Michigan University, respectively).
Relying on an RPS that would use the waste heat of decaying Plutonium 238 to power a small rear-mounted turbine, this low-power craft would take advantage of Titan’s dense atmosphere and low gravity to conduct sustained flight. A novel “climb-then-glide” strategy, where the engine would shut down during glide periods, would also allow for power to be stored for optimal use during telecommunication sessions.
This addresses a major drawback of fixed-wing vehicles, which is the need to subdivide power between the needs of maintaining flight and conducting scientific research. However, the AVIATR is limited in one respect, in that it cannot descend to the surface to conduct science experiments or collect samples.
Rotorcraft:
Last, but not least, is the concept for a rotorcraft. In this case, the aerial platform would be a quadcopter, which would be well-suited to Titan’s atmosphere, would allow for easy ascent and descent, and for studies to be conducted on the surface. It would also take advantage of developments made in commercial UAVs and drones in recent years.
Artist’s concept of the Titan Aerial Daughtercraft (TAD) flying above one of Titan’s methane lake. Credit: NASA
This mission concept would consist of two components. On the one hand, there’s the rotorcraft – known as a Titan Aerial Daughtercraft (TAD) – which would rely on a rechargeable battery system to power itself while conducting short-duration flights (about an hour at a time). The second component is the “Mothercraft”, which would take the form of a lander or balloon, which the TAD would return to between flights to recharge from an onboard RPS.
Currently, NASA’s Jet Propulsion Laboratory is developing a similar concept, known as the Mars Helicopter “Scout”, for use on Mars – which is expected to be launched aboard the Mars 2020 mission. In this case, the design calls for two coaxial counter-rotating rotors, which would provide the best thrust-to-weight ratio in Mars’ thin atmosphere.
Another rotorcraft concept is being pursued by Elizabeth Turtle and colleagues from John Hopkins APL and the University of Idaho (including James Barnes). With support from NASA and members of Goddard Space Flight Center, Pennsylvania State University, and Honeybee Robotics, they have proposed a concept known as the “Dragonfly“.
Their aerial vehicle would rely on four-rotors to take advantage of Titan’s thick atmosphere and low gravity. Its design would also allow it to easily obtain samples and determine the composition of the surface in multiple geological settings. These findings will be presented at the upcoming 48th Lunar and Planetary Science Conference – which will be taking place from March 20th to 24th in The Woodlands, Texas.
Artist’s concept of the Titan Aerial Daughter quadcopter and its “Mothercraft” balloon. Credit: NASA/STMD
While the exploration of Titan is likely to take a back seat to the exploration of Europa in the coming decades, it is anticipated that a mission will be mounted before the mid-point of this century. Not only are the scientific goals very much the same in both cases – a chance to explore a unique environment and search for life beyond Earth – but the benefits will be comparable as well.
With every potentially life-bearing body we explore, we stand to learn more about how life began in our Solar System. And even if we do not find any life in the process, we stand to learn a great deal about the history and formation of the Solar System. On top of that, we will be one step closer to understanding humanity’s place in the Universe.
ASA's Cassini spacecraft looks toward the night side of Saturn's largest moon and sees sunlight scattering through the periphery of Titan's atmosphere and forming a ring of color.
Credit: NASA/JPL-Caltech/Space Science Institute
Last week – from Monday, February 27th to Wednesday, March 1st – NASA hosted the “Planetary Science Vision 2050 Workshop” at their headquarters in Washington, DC. In the course of the many presentations, speeches and panel discussions, NASA’s shared its many plans for the future of space exploration with the international community.
Among the more ambitious of these was a proposal to explore Titan using an aerial explorer and a lander. Building upon the success of the ESA’s Cassini-Huygen mission, this plan would involve a balloon that would explore Titan’s surface from low altitude, along with a Mars Pathfinder-style mission that would explore the surface.
Ultimately, the goal a mission to Titan would be to explore the rich organic chemical environment the moon has, which presents a unique opportunity for planetary researchers. For some time, scientists have understood that Titan’s surface and atmosphere have an abundance of organic compounds and all the prebiotic chemistry necessary for life to function.
Artist depiction of Huygens landing on Titan. Credit: ESA
“Titan’s of particular interest because the abundant and complex organic chemistry can teach us about chemical interactions that could have occurred here on Earth (and elsewhere?) leading to the development of life. Furthermore, not only does Titan have an interior liquid-water ocean, but there will also have been opportunities for organic material to have mixed with liquid water at Titan’s surface, for example impact craters and possibly cryovolcanic eruptions. The combination of organic material with liquid water, of course, increases astrobiological potential.”
For this reason, the exploration of Titan has been a scientific goal for decades. The only question is how best to go about exploring Titan’s unique environment. During previous Decadal Surveys – such as the Campaign Strategy Working Group (CSWG) on Prebiotic Chemistry in the Outer Solar System, of which Lorenz was a contributor – has suggested that a mobile aerial vehicle (such as an airship or a balloon) would well-suited to the task.
However, such vehicles would be unable to study Titan’s methane lakes, which are one of the most exciting draws of the moon as far as research into prebiotic chemistry goes. What’s more, an aerial vehicle would not be able to conduct in-situ chemical analysis of the surface, much like what the Mars Exploration Rovers (Spirit, Opportunity and Curiosity) have been doing on Mars – and with immense results!
The ESA’s TALISE (Titan Lake In-situ Sampling Propelled Explorer) on the left, and NASA’s Titan Mare Explorer (TiME) on the right. Credit: bisbos.com
At the same time, Lorenz and his colleagues examined concepts for the exploration of Titan’s hydrocarbon seas – like the proposed Titan Mare Explorer (TiME) capsule. As one of several finalists of NASA’s 2010 Discovery competition, this concept called for the deployment of nautical robot to Titan in the coming decades, where it would study its methane lakes to learn more about the methane cycle and search for signs of organic life.
While such a proposal would be cost-effective and presents some very exciting opportunities for research, it also has some limitations. For instance, during the 2020s-2030s, Titan’s northern hemisphere will be experiencing its winter season; at which point the thickness of its atmosphere will make direct-to-Earth communications and Earth views impossible. On top of that, a nautical vehicle would preclude the exploration of Titan’s land surfaces.
These offer some of the most likely prospects for studying Titan’s advanced chemical evolution, including Titan’s dune sands. As a windswept region, this area likely has material deposited from all over Titan and may also contain aqueously altered materials. Much as the Mars Pathfinder landing site was selected so it could collect samples from a wide area, such as location would be an ideal site for a lander.
As such, Lorenz and his colleagues advocated the type of mission that was articulated in the 2007 Flagship Study, which called for a Montgolfière balloon for regional exploration and a Pathfinder-like lander. This would provide the opportunity to conduct surface imaging at resolutions that are impossible from orbit (due to the thick atmosphere) as well as investigating the surface chemistry and interior structure of the moon.
Artist’s conception of a possible structure for underground liquid reservoirs on Saturn moon’s Titan. Credit: ESA/ATG medialab
So while the balloon would gather high-resolution geographical data of the moon, the lander could conduct seismological surveys that would characterize the thickness of the ice above Titan’s internal water ocean. However, a lander mission would be limited in terms of range, and the surface of Titan presents problems for mobility. This would make multiple landers, or a relocatable lander, the most desired option.
“Potential targets include areas where we can measure solid surface materials, the composition of which is still not well known, Titan’s dune sands, for example,” said Turtle. “Detailed in situ analysis is required to determine their composition. The lakes and seas are also intriguing; however, in the nearer term (missions arriving in the 2030s) most of those will be in winter darkness. So, exploring them would likely have to wait until the 2040s.”
This mission concept would also take advantage of several technological advances that have been made in recent years. As Lorenz explained in the course of the presentation:
“Heavier-than-air mobility at Titan is in fact highly efficient, moreover, improvements in autonomous aircraft in the two decades since the CSWG make such exploration a realistic prospect. Multiple in-situ landers delivered by an aerial vehicle like an airplane or a lander with aerial mobility to access multiple sites, would provide the most desirable scientific capability, highly relevant to the themes of origins, workings, and life.”
Updated maps of Titan, based on the Cassini imaging science subsystem. Credit: NASA/JPL/Space Science Institute
However, addressing some additional challenges not raised at the 2050 Vision Workshop, they will be presenting a slight twist on their idea. Instead of a balloon and multiple landers, they will present a mission concept involving a “Dragonfly” qaudcopter. This four-rotor vehicle would be able to take advantage of Titan’s thick atmosphere and low gravity to obtain samples and determine the surface composition in multiple geological settings.
This concept also incorporates a lot of recent advances in technology, which include modern control electronics and advances in commerical unmanned aerial vehicle (UAV) designs. On top of that, a quadcopter would do away with chemically-powered retrorockets and could power-up between flights, giving it a potentially much longer lifespan.
These and other concepts for exploring Saturn’s moon Titan are sure to gain traction in the coming years. Given the many mysteries locked away on this world – with includes abundant water ice, prebiotic chemistry, a methane cycle, and a subsurface ocean that is likely to be a prebiotic environment – it is certainly a popular target for scientific research.
