Titan News 2020
May 31, 2020 : What Types Of Hydrocarbons Or Organics Could We Encounter On The Opaque Moon Titan ?
The giant moon of Saturn Titan is known to contain a thick and deep atmosphere dominated by nitrogen like our own atmosphere. However, Titan's atmosphere is devoid of any significant concentration of oxygen but it contains a relatively significant concentration of methane. Methane whose chemical formula is CH4 is a simple molecule composed of one carbon atom and four hydrogen atoms. A parallel between the behavior of methane on Saturn's largest moon and the behavior of water on Earth can be drawn. Methane can be present as a gas or as a liquid on Titan and water can also be present as a gas or as a liquid on Earth. Water can also be present in the form of snow or ice on Earth if the environmental temperature is sufficiently low. In an environment where the atmospheric pressure is around the mean atmospheric pressure of the Earth at sea level, water can appear as ice or snow if the environmental temperature is below or equal to 0 degree Celsius (about 273.15 Kelvin or 32 degrees Fahrenheit). Can methane appear as ice or snow on the surface of Titan ? The harsh environment of the Opaque Moon has the right conditions for the presence of stable liquid methane on its surface but it may not be extreme enough for the presence of large amounts of solid methane on the surface.
The radar images obtained from the Radar Mapper of the Cassini orbiter during its long mission in the Saturn System from 2004 to 2017 have clearly revealed the presence of humid areas dominated by methane or ethane. The humid areas turn out to be mostly found in the high latitudes of the northern hemisphere. The low or mid-latitudes of the Orange Moon seem relatively dry whereas the polar areas seem less dry or more humid. The first pool of stable liquids identified on Titan was found in the high latitudes of the southern hemisphere. Prior to that major finding, we had suspected the potential presence of lakes, seas, rivers or even oceans in the dark areas of Titan. The infrared or near-infrared views as well as the radar images acquired from the Cassini orbiter have clearly shown that the suspected ocean of methane or ethane is absent but that there are lakes, seas and rivers in the polar regions of the giant moon. How can we explain that the lakes, seas and rivers are mostly concentrated in the high latitudes or in the polar regions ? How can we explain the fact that the north polar region is by far the most humid area on Titan today ?
The image in the upper part of the table reveals a raw image of a portion of Titan obtained on May 31, 2013 from the Cassini orbiter. The view whose file name is N00210429.jpg was acquired on the basis of the CL1 filter and of the CB3 filter. The image had not been validated or calibrated at the time of the observation and a validated or calibrated view was going to be archived with the Planetary Data System proposed by NASA. The image in the lower part of the table represents a colorized version of the original view. A sharp contrast between surface features can be clearly identified. Credit for the original view: NASA/JPL-Caltech/Space Science Institute. Credit for the colorization process: Marc Lafferre, 2020.
April 21, 2020 : The Environmental Conditions On Titan May Allow The Potential Presence Of Dust Devils Likely To Engender Dunes According To A New Study Involving Brian Jackson
A new research work entitled « Dust Devils on Titan », published in AGU's journal Geophysical Research Letters and proposed by a team involving Brian Jackson suggests that Saturn's largest moon Titan may have the right environmental conditions to allow the potential presence of dust devils like on the Earth or Mars. Titan is known to contain vast systems of linear and parallel dunes extending over long distances. The shape of those dunes is closely related to prevailing winds. Planetologists imagine the potential influence of dust devils on the dynamics or the shape of the dunes in the relatively dry environment found at low or mid-latitudes on that enigmatic moon of the Ringed Planet. In the opaque and dense atmosphere of Titan, the power of winds can engender a strong erosion of the soil. The nature and the dynamics of the sand of Titan represent key topics for planetologists today. On the basis of radar data obtained from the Cassini spacecraft during its long mission in the Saturn System from 2004 to 2017, they can deduce or evaluate the potential influence of whirlwinds on the concentration of dust at the level of the soil.
The huge amount of data acquired from the Cassini orbiter has allowed us to determine that dunes on Titan are mostly found in the low or mid-latitudes of the giant moon and represent, approximately, 30 percent of the surface. The specialists have been in a position to identify a large dust storm during the Cassini-Huygens mission in the Saturn System. The sand grains and the dust of the dunes may be the outcome of a type of snowfall of hydrocarbons or organics from the haze as Brian Jackson, who is a planetary scientist at Boise State University in Idaho and who is the lead author of the research work, suggests. The heavier molecules of the haze may fall toward the surface to form the dunes we observe in radar images from the orbiter. The appearance of the dunes is a mystery but some researchers imagine that they may have a plasticky texture or that they may be quite different from the dunes one can encounter on the Earth or on the Red Planet Mars. We all have in mind the big dust storms encountered in Australia or the relatively recent global storm of Mars but, surprisingly, the dust devils can generate more dust than the typical dust storms on our planet. The dynamics of the soil that they engender is different in each configuration.
The image in the upper part of the table corresponds to a raw view of the disk of Saturn's largest moon Titan. The view whose file name is N00194383.jpg was obtained with the CL1 filter and the MT3 filter of the Cassini orbiter on August 30, 2012. The snapshot had not been validated or calibrated at the time of the observation and a validated or calibrated image was going to be archived with the Planetary Data System proposed by NASA. A vortex can be discerned above the south polar area of the giant moon in particular. The view in the lower part of the table represents a colorized version of the original view. Credit for the raw image: NASA/JPL-Caltech/Space Science Institute. Credit for the colorization of the original view: Marc Lafferre, 2020.
April 14, 2020 : A New Laboratory Experiment Reveals How The Methane Found On Neptune Or Titan Potentially Formed In Interstellar Space
A new research work entitled « An experimental study of the surface formation of methane in interstellar molecular clouds », published on April 13, 2020 in the journal Nature Astronomy and proposed by a team of scientists involving Danna Qasim unveils laboratory experiments upon the potential formation of methane in the harsh environment of space far from any star. The formation of methane in interstellar molecular clouds may be closely related to the presence of water ice or icy dust grains. The simulations performed in a laboratory at Leiden University in the Netherlands confirm the prevailing assumptions on the mechanisms that lead to the formation of methane in the Outer Solar System or beyond. Reproducing the harsh environment of interstellar space is clearly a challenge but the team of researchers was in a position to obtain a significant outcome regarding the potential interactions in the soup of molecules, particles or radiations encountered between stars. Methane is widespread in the Outer Solar System, from the giant moon Titan to Gas Giants or Ice Giants like Uranus or Neptune. Many worlds found beyond the Inner Solar System like Pluto or Charon may be relatively rich in organics, hydrocarbons or methane.
Methane whose chemical formula is CH4 represents the simplest stable hydrocarbon molecule. It contains one carbon atom and 4 hydrogen atoms. Methane can be encountered on Earth in the form of natural gas. In the environment of the Earth at sea level, methane can only be found as a gas because the ambient temperature is much too high for the molecule to appear in its liquid form or in its solid form for instance. Everyone knows that, in a typical environment, methane represents a flammable gas that takes shape from decaying organic molecules. That's also the case for other hydrocarbons like ethane (C2H6), propane (C3H8), butane (C4H10) or for the typical fuel of our cars. Thanks to the Cassini-Huygens mission, we know, now, that there are lakes, seas or rivers dominated by methane on Saturn's largest moon Titan. The opaque atmosphere of that moon contains a relatively significant concentration of methane. The Gas Giants are dominated by hydrogen and helium but they also contain a relatively significant fraction of methane. Astronomers have been in a position to determine that methane ice represents one of the ten most abundant ices identified in interstellar space.
The image above reveals Neptune, Titan and Uranus, three worlds of the Outer Solar System containing relatively significant concentrations of methane in their atmosphere. Methane represents, approximately, 1.4 percent of the composition of Titan's atmosphere for instance. Credit for the original view of Neptune: NASA/JPL. Credit for the original view of Titan: NASA/JPL-Caltech/Space Science Institute. Credit for the original view of Uranus: NASA/JPL. Montage credit: Marc Lafferre, 2020.
March 26, 2020 : A New Research Work Suggests That LUVOIR-A May Allow Us To Identify Exoplanets Unveiling A Titan-Like Atmosphere
A new research work entitled « Study of Barnard's Star B as an Analog for 'Titan-like' Exoplanets » and proposed by a team involving R. Felton was presented at the 235th meeting of the American Astronomical Society in January 2020. The new study suggests that a space-based telescope like LUVOIR-A may allow us to study the characteristics of the atmosphere of an exoplanet like Barnard's Star b, an exoplanet which evolves around Barnard's Star, one of the nearest stars to the Sun. Barnard's Star represents a Red Dwarf located approximately 6 light-years away from us. Barnard's Star is part of the same category of stars as Proxima Centauri for instance. Those stars are less warm than our star which implies that the Habitable Zone will appear closer to the star. Researchers easily imagine worlds that look like Titan to a certain extent around a Red Dwarf like Barnard's Star. The particular characteristics of Titan's atmosphere can tell us a lot regarding the potential worlds we could encounter beyond the Solar System. The relatively big icy worlds or Terrestrial worlds are likely to contain an opaque atmosphere like the atmosphere of Venus or the atmosphere of Titan.
The mass of the exoplanet Barnard's Star b or Barnard b may represent at least 3.2 times the mass of the Earth. The relatively big extrasolar planet may evolve near the snow line of the relatively small star. Astronomers will have to confirm that outcome which is based on recent radial velocity measurements. On the basis of the apparent periodical movement of the star, one can deduce the presence of an exoplanet around it due to the gravitational interactions in the system. The researchers of the study believe that Barnard b is a rocky planet like the Earth or Venus and that it is covered in a thick atmosphere that may look like the atmosphere of Saturn's largest moon Titan. The planetologists know the surface temperature of the star. Therefore, they can infer the potential environmental temperature of any world at a particular distance from the star. If the exoplanet is larger than the Earth and much smaller than Neptune or Uranus, one can assume that the exoplanet may be a rocky world or an icy world. In the Outer Solar System, the atmospheres tend to be relatively rich in methane. That's the case for the deep and opaque atmosphere of Titan. That's also the case for Neptune or Uranus.
The image in the upper part of this table represents a raw view of Saturn's largest moon Titan obtained on March 14, 2013 from the eye of the Cassini orbiter. The file name of the raw view is N00204034.jpg. The view was acquired on the basis of the CL1 and MT3 filters. At the time of the observation, the image had not been validated or calibrated and a validated or calibrated image was going to be archived with the Planetary Data System proposed by NASA. One can discern, in particular, a vortex in the lower part of the disk. The image in the lower part of this table represents a colorized version of the original view. Credit for the original view: NASA/JPL-Caltech/Space Science Institute. Credit for the colorization of the original view: Marc Lafferre, 2020.
March 10, 2020 : A New Study Involving Yuri Fujii Demonstrates That A Large Exomoon Similar To Titan Can Take Shape In A Safety Zone Around A Gas Giant
A new study entitled « Formation of single-moon systems around gas giants », published in Astronomy and Astrophysics in March 2020 and proposed by a team composed of Yuri Fujii and Masahiro Ogihara demonstrates the potential development of a large moon similar to Titan in the safety zone of a circumplanetary disk. The researchers performed several simulations of the formation process of moons around a Gas Giant on the basis of the PC Cluster operated by the National Astronomical Observatory of Japan (NAOJ). Numerical simulations reveal that the temperature gradient in the gas disk around any Gas Giant in its formation process or in its youth plays a key role in the development of a large moon comparable to Saturn's largest moon Titan. The planetologists show that the dust of the disk evolving around the young Gas Giant can generate a « safety zone » that prevents the world from being swallowed by the big planet as the system develops. A major goal is to understand or to determine the mechanisms that have led to the current orbital configuration of the numerous moons of Saturn. The system of the Ringed Planet is, to a certain extent, a mini Solar System.
Specialists of the Solar System believe that numerous moons present in the Solar System took shape around their planet during its formation process. Those moons may have emerged in the disk of gas and dust evolving around the planet in its youth or in its formation process. One can imagine a disk of gas, dust, ice, comets, asteroids and planetesimals spinning around the young planet like cars in the Indianapolis Motor Speedway. However, the current configuration of the orbit and distribution of the moons in the Saturn System can't be correctly explained by previous simulations which result in configurations where all large moons are attracted and swallowed by the Gas Giant or in configurations where multiple large moons take shape and become stable around the Gas Giant. Today, the Saturn System which has been largely explored by the Cassini spacecraft and by the Huygens probe between 2004 and 2017 is composed of the second largest moon in the Solar System and is composed of numerous icy moons which are much smaller than Titan. That configuration with a big moon and many small moons is not a potential outcome of previous simulations. That's why new models had to be envisaged.
The image above reveals the disk of Titan as well as a portion of the disk of the icy moon Tethys where a giant crater can be clearly seen. The view was taken from the ISS Narrow-Angle Camera of the Cassini spacecraft on November 26, 2009. Tethys whose diameter is over 1000 km evolves much closer to Saturn than the Opaque Moon. Image credit: NASA/JPL-Caltech/Space Science Institute.
February 26, 2020 : How Can We Explain The Attractiveness Of Titan In The Prospect Of The Dragonfly Mission ?
The engineers and scientists from NASA are preparing the Dragonfly mission to study Titan, a fascinating moon of Saturn. Why has Titan been a key target for planetologists ? The Cassini/Huygens mission which represents the latest mission to the Saturn System came to an end in 2017. During its long mission in the Saturn System which had started in 2004, we have had the opportunity to discover a fantastic world which looks like the Earth to a certain extent. There are lakes, seas, rivers, mountains, dunes, canyons, cloud systems or rainfall events on Titan like on Earth. Researchers believe that there is also a subsurface ocean dominated by liquid water beneath the presumed icy crust of the giant moon. That intriguing world was discovered by Christiaan Huygens in 1655 who called it « Luna Saturni ». Thanks to the 127 close flybys of the Opaque Moon and thanks to the data obtained from the Huygens probe during its extraordinary journey of January 14, 2005, we are starting to better understand Saturn's largest moon and new mysteries emerge. The Dragonfly mission may allow us to obtain key data regarding the landscape, the chemistry and the habitability of Titan.
Titan is a captivating world for many reasons. The giant moon is covered in a thick and opaque atmosphere which is clearly unique in the Solar System. Ganymede which is the largest moon in the Solar System is devoid of any atmosphere for instance. The presence of an atmosphere engenders a meteorology and erosional processes. The atmosphere is likely to fuel or accelerate chemical reactions. Titan's atmosphere is so dense and thick that the atmospheric pressure on its surface is higher than that of the Earth at sea level. Thus, the air is four times denser at the level of Titan's surface than our air at sea level. The opaque atmosphere of Titan, identified as soon as 1944 by the Dutch-American astronomer Gerard Kuiper, prevents us from discerning surface features from outer space. The Dragonfly drone will benefit from a particularly low gravity which is lower than the gravity of the Moon and from a relatively dense air which are likely to facilitate the flight of the probe. However, the drone will have to withstand the particularly low environmental temperatures representing around minus 290 degrees Fahrenheit, minus 179 degrees Celsius or 94 Kelvin. The Dragonfly drone may fly more than 100 miles or 160 kilometers during its mission which may last about 3 years.
The image in the upper part of this table unveils a raw view of a portion of Saturn's largest moon Titan obtained from the Cassini orbiter on May 28, 2008. The image whose file name is N00111153.jpg was acquired with the CL1 filter and the MT1 filter. The view which had not been validated or calibrated in the period of the observation was going to be archived with the Planetary Data System proposed by NASA. The image in the lower part of the table represents a colorized version of the original image. One can clearly discern the upper part of Titan's atmosphere. Credit for the raw image: NASA/JPL-Caltech/Space Science Institute. Credit for the colorization of the original image: Marc Lafferre, 2020.
February 19, 2020 : New Quantum Mechanical Calculations Upon Azotosomes Imply That Their Development Is Unlikely In The Hypothetical Biosphere Of Titan
A new study entitled « Can polarity-inverted membranes self-assemble on Titan ? », published in Science Advances on January 24, 2020 and proposed by H. Sandström and M. Rahm, reveals quantum mechanical calculations upon azotosomes which imply that those molecules which represent nitrogen-containing compounds may not develop in the hypothetical biosphere of Titan. In a relatively recent past, some researchers had advanced the possibility of a Titanian biosphere involving azotosomes. Azotosomes appeared to be good candidates for the potential development of cell membranes of any exotic lifeform on Saturn's largest moon. The new research work tends to show that azotosomes are unlikely for any autonomous organism on the Hazy Moon. The scientists advance that in an environment where temperatures are extremely low and where liquid water is absent, cell membranes can be ruled out for any lifeform. In terms of thermodynamics, the formation and the development of azotosomes on the Opaque Moon appear unlikely. Those theoretical membranes may not be in a position to self-assemble in the extreme environment of the giant moon.
On the basis of what we observe in our own biosphere, we have had the opportunity to determine that the membranes of the cells play a key role for the development of typical organisms. The membranes of the cells are composed of lipid bilayers which are hydrophobic or amphiphilic. Life on Earth is based on liquid water and all creatures are composed of cells in which various chemical reactions can take shape without the potential disruptions in the potential interactions between liquid water and other compounds located outside the cell and the « factory » of the cell. Numerous researchers believe that the lipid bilayer membrane is a key aspect of life in an environment dominated by liquid water or in an environment where water can be found in its liquid form. In the Solar System, the Earth is the only planetary body where water can be encountered in its liquid form on the surface. On Mars, there are not the right combinations of atmospheric pressure and environmental temperature for the stable presence of liquid water on the surface for instance. On Venus, the greenhouse effect is so high that the environmental temperature at the level of the surface is too high for the presence of liquid water on the surface.
The image in the upper part of this table reveals a raw view of Saturn's largest moon Titan obtained on September 12, 2017 from the Cassini spacecraft. The image whose file name is N00289163.jpg was acquired using the CL1 filter and the CB3 filter. The image had not been validated or calibrated at the time of the observation and was going to be archived with the Planetary Data System proposed by NASA. The image in the lower part of this table represents a colorized view of the raw image. One can clearly notice a portion of Kraken Mare. Credit for the raw image: NASA/JPL-Caltech/Space Science Institute. Credit for the colorization of the original image: Marc Lafferre, 2020.
January 27, 2020 : Some Researchers Have Suggested At The 235th Meeting Of The American Astronomical Society That The Haze Of Pluto May Resemble The Haze Of Titan
A group of researchers has revealed, during a presentation on January 8, 2020 at the 235th meeting of the American Astronomical Society taking place in Honolulu in the state of Hawaii, that the haze identified in the atmosphere of the Dwarf Planet Pluto may look like the haze of Saturn's largest moon Titan. Researchers had collected a huge amount of data regarding Titan's atmosphere during the Cassini-Huygens mission in the Saturn System from 2004 to 2017. On July 14, 2015, the New Horizons spacecraft performed the first flyby of Pluto and Charon revealing a remarkably complex world with a varied landscape and with a thin atmosphere composed of several layers. In fact, researchers were in a position to determine that Pluto's atmosphere is a blue atmosphere like the atmosphere of our planet and that a haze evolves in that exotic gas blanket. The team involving Bonnie Buratti who is a planetary scientist at NASA's Jet Propulsion Laboratory in California advanced that the haze of Pluto is rich in organics like the haze of Titan. The atmosphere of Pluto is particularly thin like the atmosphere of Neptune's largest moon Triton but the haze of Pluto may be closer to the haze of Titan in terms of composition.
Pluto and Triton represent small worlds whose size is roughly similar. Those planetary bodies appear to be remarkably active in terms of geology. In spite of their relatively low gravity, they contain a thin atmosphere dominated by nitrogen. Most moons or icy bodies in the Solar System are devoid of any atmosphere but Titan, Triton and Pluto unveil an atmosphere. There is apparently the right combination of environmental temperature and gravity on each planetary body to allow the presence of an atmosphere. The atmosphere of Titan is reminiscent of the atmosphere of the Early Earth and of the Earth today because that gas layer is mostly composed of molecular nitrogen. Unlike the atmosphere of Pluto and Triton, the atmosphere of the Orange Moon appears completely opaque from outer space in the visible spectrum. The global haze of Saturn's largest moon prevents us from discerning surface features from outer space. The atmosphere of Pluto appears more optically thick than the atmosphere of the strange moon of Neptune Triton. The difference may be related to a carbon-rich haze in the environment of Pluto. The reddish areas observed on Pluto imply the potential presence of tholins, a type of mud or sludge rich in organics and hydrocarbons.
The image above reveals a portion of Titan in the lower part of the view as well as a portion of Pluto in the upper part of the view. The original view of Titan was obtained on January 30, 2012 from the Cassini spacecraft. The original view of Pluto was obtained on July 14, 2015 from the New Horizons spacecraft. The views of Titan and Pluto are at scale. Each side of the image represents about 1000 km. One can notice, in particular, a multitude of layers in Pluto's atmosphere and a detached haze layer in Titan's atmosphere. A parallel can be drawn between the haze on Titan and the haze on Pluto. Credit for the original view of Titan: NASA/JPL-Caltech/Space Science Institute. Credit for the original view of Pluto: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute. Credit for the montage: Marc Lafferre, 2020.
January 17, 2020 : Some Researchers May Have Solved The Mystery Of The Reversed Spin Of The Huygens Probe During Its Atmospheric Descent
About 15 years ago, on January 14, 2005, the Huygens probe released from the Cassini orbiter performed an atmospheric descent and landed on the surface of Saturn's largest moon Titan for the first time in history. The Huygens probe which was proposed by ESA and ASI had separated from the Cassini spacecraft proposed by NASA at the end of December 2004. During the atmospheric plunge of January 14, 2005, the Huygens probe started to spin the wrong way and engineers and researchers had not anticipated that configuration. That mystery may have been solved thanks to recent tests or simulations. In fact, during the atmospheric journey, some instruments of the probe may have generated an unexpected torque opposite to that engendered by the 36 angled vanes of the Huygens probe. The vanes played a key role since they were used to control the rotation of the probe during its descent inside the deep and thick atmosphere of the giant moon. The atmosphere of Titan like the atmosphere of Venus or like the atmosphere of Mars makes any parachute useful for any probe that dives to the surface.
Researchers have been in a position to determine that two devices of the Huygens probe, the Separation Subsystem (SEPS) and the Radar Altimeter (RA) antennae, actually engendered an unexpected torque opposite to that generated by the multiple vanes. That phenomenon was strengthened due to the alteration of the gas flow around the atmospheric probe by the vanes which led to a rise in the amplitude of the « negative torque ». Let's point out that the negative torque corresponds to the effect that made the Huygens module flip its direction of rotation. The unexpected effect turned out to exceed the influence of the vanes. It is crucial for engineers to clearly understand the mechanisms that led to the unexpected configuration in the prospect of the development of future probes sent to extraterrestrial atmospheres like the atmosphere of Venus, Mars, Titan or the four Gas Giants. The behavior of any atmospheric probe can engender scientific failures. That's why engineers and scientists must be in a position to anticipate any scenario during the complex phase of the atmospheric descent.
The image above represents a mosaic of aerial views of Titan's landscape obtained from the DISR of the Huygens probe during its atmospheric plunge on January 14, 2005. The views were acquired at an altitude of approximately 8 km and the resolution of the landscape features is about 20 meters per pixel. One can clearly notice a sharp contrast between bright hills composed of a network of dark channels and a dark plain which seems quite uniform. The Cassini-Huygens mission represented the outcome of a collaboration between ESA, NASA and ASI. Image credit: ESA/NASA/JPL/University of Arizona.
January 7, 2020 : A New Research Work Involving Takahiro Iino Reveals That ALMA Has Measured The 14N/15N Isotopic Ratio In CH3CN Of The Opaque Atmosphere Of Titan
A new research work proposed on January 7, 2020 by a team of researchers composed of Takahiro Iino, Hideo Sagawa and Takashi Tsukagoshi and presented in Arxiv reveals the measurement of the 14N/15N isotopic ratio in CH3CN in the atmosphere of Saturn's largest moon Titan via ALMA. The planetologists were in a position to detect submillimeter rotational transitions of CH3C15N found at the 338 GHz band in the spectra of Titan's opaque atmosphere thanks to the analysis of archival data collected by the Atacama Large Millimeter/submillimeter Array (ALMA). A comparison between those observations and the simultaneously observed CH3CN lines at the 349 GHz band, which allow us to study the area from the altitude of 160 km to the altitude of about 400 km, allowed the researchers to deduce the value of the ratio 14N/15N in CH3CN at about 125. The level of accuracy remains limited but it allows the scientists to advance that the value of 14N/15N for CH3CN is higher than the values that have been previously determined and theoretically predicted for HCN and HC3N. The difference may be related to the different N2 dissociation factors whose impact depends on the altitude as proposed by a recent photochemical model.
The isotopic ratio between 14N and 15N can vary in the various nitriles present in Titan's atmosphere. The differences are closely related to the production processes of the molecules. The dissociation processes of N2 can be generated via the action of ultraviolet light from the Sun, via the action of magnetospheric electrons or via the action of galactic cosmic rays. Regarding the nitrile CH3CN, a photochemical model predicted a value of 120-130 in the lower part of the stratosphere for the isotopic ratio 14N/15N. The expected value is much higher than that for the nitriles HCN and HC3N which is, approximately, between 67 and 94. The value of 125 for the ratio 14N/15N in the molecule CH3CN which was measured by ALMA appears clearly higher than the value measured and predicted for the ratio 14N/15N in the molecules HCN and HC3N. The dissociation factors which depend on the altitude must be considered. Researchers are particularly interested in the chemistry of Titan's complex atmosphere which represents, to a certain extent, a soup of various molecules, elements or ions and which may resemble the atmosphere of the Early Earth.
The image in the upper part of the table reveals a raw image of Titan's disk obtained from the Cassini spacecraft on December 14, 2009. The image whose file name is N00148433.jpg was acquired using the CL1 filter and the MT3 filter. The view had not been validated or calibrated. A validated or calibrated view was going to be archived with the Planetary Data System proposed by NASA. The image in the lower part of the table represents a colorized version of the raw image. Credit for the raw image: NASA/JPL-Caltech/Space Science Institute. Credit for the colorization of the raw image: Marc Lafferre, 2020.
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