Titan News 2019
May 23, 2019 : How Can We Explain The Apparent Contrast Between The Relatively High Level Of Internal Activity Of Enceladus, Titan Or Dione And The Relatively Low Level Of Internal Activity Of Moons Like Mimas Or Rhea ?
The System of Saturn is rich in mysteries. Some moons like Enceladus or Titan seem particularly active in terms of geology or internal activity whereas other moons like Mimas or Rhea seem to be inactive or much less active than those well-known worlds of the Gas Giant. Among the 62 moons orbiting the second largest Gas Giant in the Solar System, one can notice that most worlds orbiting Saturn are devoid of any atmosphere and unveil a highly cratered surface. In fact, Titan is the only moon of the Ringed Planet containing a significant atmosphere. That exotic atmosphere mainly composed of nitrogen appears completely opaque from outer space in the visible spectrum due to the presence of a haze of hydrocarbons or organics. The origin of Titan's atmosphere is undoubtedly one of the major mysteries in planetology today. Thanks to the Cassini mission, we have become aware that a tiny moon can be geologically active. The south polar region of Enceladus, a bright and icy moon of Saturn, unveils geysers rich in water. The geysers appear in the famous « Tiger Stripes » which are topographic fractures.
Thanks to the Cassini-Huygens mission, we have been in a position to determine that there are lakes, seas and rivers in the high latitudes of Saturn's largest moon Titan. Titan which is bigger than the Moon or Mercury is clearly an active world with a dynamic atmosphere and a complex meteorology. Clouds of methane or ethane can take shape. Vortices can also develop above each polar region of the Opaque Moon. Planetologists believe that there is an internal ocean of liquid water beneath the external crust of Titan and Enceladus. The cratered moon Dione is also suspected to harbor an internal ocean of liquid water. By contrast, moons like Tethys, Rhea or Iapetus may be inactive or less active than Titan, Enceladus and Dione. How can we explain that dichotomy in terms of dynamics or internal activity among the numerous moons of Saturn ? Some moons of Saturn unveil strange shapes like Pan or Atlas which look like a ravioli. How can we explain those unusual shapes ? Are those moons young ? What are the interactions between those small moons and Saturn's rings ?
The image above reveals the crescent of Enceladus and Titan, two active worlds orbiting the Gas Giant Saturn. The image represents a natural color view produced on the basis of data obtained from the Narrow-Angle Camera of the Cassini orbiter on February 5, 2006. Views acquired using red, green and blue spectral filters were mobilized to generate the final image. The tiny moon Enceladus appears 4.1 million kilometers or 2.5 million miles from the camera whereas the Opaque Moon Titan appears 5.3 million kilometers or 3.3 million miles from the camera. Image credit: NASA/JPL/Space Science Institute.
May 18, 2019 : There Are Storms On Titan And On The Earth Like On Many Other Worlds In The Solar System
Clouds of water are widespread on our planet. Most of the surface of the Earth is covered by liquid water. There are rivers, lakes, seas as well as oceans on the Blue Planet. A meteorological cycle involving liquid water can be observed. That meteorological cycle is characterized by evaporation processes, condensation processes and precipitation processes. Sunlight, environmental heat or seasonal factors play a key role in the dynamics of our meteorology. Thanks to the Cassini-Huygens probe, we have been in a position to determine that there is also a meteorological cycle on Saturn's largest moon Titan. That meteorological cycle appears particularly exotic since it is based on methane rather than water. The environmental temperature at the level of the surface on Titan is so low that methane can appear in its liquid form on the surface. Radar data as well as infrared or near-infrared data acquired from the Cassini orbiter during its long mission in the System of Saturn and its numerous moons have clearly shown that there are lakes, seas and rivers on Titan.
In the first half of the
Cassini-Huygens mission in the Saturn System, the eyes of the Cassini orbiter
have clearly revealed dynamic cloud systems in the south polar region of the
Opaque Moon. That region was experiencing the Summer season. The first body of
surface liquid clearly identified on Titan was Ontario Lacus, a large pool of
liquid composed of methane and ethane. Later in the Cassini mission, a giant
vortex or cyclone engulfing the north polar region was identified from the
orbiter. Radar data obtained from the Radar Mapper of the Cassini spacecraft
have clearly shown that the most humid areas on Titan are found in the high
latitudes of the northern hemisphere. Cirrus-like clouds evolving at a high
latitude around the north polar region have been clearly identified at the end
of the Cassini mission in the Saturn System. Large cloud systems developing
above the low or mid-latitudes of the giant moon have been observed in 2010,
at the start of the Autumn season in the southern hemisphere and of the Spring
season in the northern hemisphere. In 2012, a vortex evolving above the south
polar region of Titan was clearly identified from the Cassini probe. Titan and
the Earth appear to be paradises for the study of storms or cyclones but
several other worlds in the Solar System unveil a dynamic atmosphere.
The image in the upper part of this table
reveals the disk of Titan unveiling a multitude of clouds at a
relatively low latitude on the Opaque Moon. The image was produced on the basis of
data obtained from the Narrow-Angle Camera of the Cassini orbiter on
October 18, 2010. The view is the outcome of data acquired using a
filter sensitive to near-infrared radiation centered at 938 nanometers
as well as data obtained using a filter sensitive to visible radiation
centered at 619 nanometers. The relatively high level of cloud activity
at low latitudes or mid-latitudes on Titan is completely unusual and may
be closely related to seasonal changes.
Credit for the view
of Titan's disk: NASA/JPL/Space Science Institute.
May 1st 2019 : A New Study Reveals A Giant Belt Of Ice-Rich Bedrock In The Tropical Area Of Titan Implying A Potential Tectonic Activity
A new study entitled « A corridor of exposed ice-rich bedrock across Titan's tropical region », recently published in the journal Nature Astronomy and led by Caitlin Griffith, a professor in the UA Lunar and Planetary Laboratory, unveils a giant corridor of ice-rich bedrock in the Tropical area of Saturn's largest moon Titan. That belt extending over long distances may potentially be the outcome of a significant tectonic activity in the long history of Titan's geology. The discovery of that enigmatic corridor was performed thanks to a research work upon the origin of the methane observed on Titan. Methane whose chemical formula is CH4 can be found in the atmosphere of the Opaque Moon as well as on its surface. Titan's atmosphere is completely opaque in the visible spectrum from outer space but thanks to several instruments of the Cassini orbiter and thanks to the Huygens probe which landed onto Titan's surface on January 14, 2005, we have been in a position to gather major clues regarding the Titanian geology or the nature of Titan's surface.
At low or mid-latitudes, in the infrared or near-infrared spectrum, a significant contrast between relatively low-albedo areas and relatively high-albedo areas can be discerned. The panoramic views obtained from the Huygens probe during its unforgettable atmospheric descent in the hazy atmosphere clearly revealed a major contrast between bright hills and a dark or brown plain. Those bright hills found at a relatively low latitude close to the Equator may be dominated by water ice. The brown or dark areas may be rich in methane, hydrocarbons or organics. The radar data acquired from the Cassini orbiter, during the Cassini mission in the Saturn System from 2004 to 2017, have clearly shown that the dark areas found at low or mid-latitudes and which mark a sharp contrast with bright areas are dominated by linear and parallel dunes extending over long distances. Those dunes are reminiscent of the Seif dunes found in the Namib Desert for instance. By contrast, the dark and uniform areas located in the high latitudes or in the polar regions of the Orange Moon represent pools of liquid.
The image above reveals a global view of Titan based on data acquired with the Radar Mapper and with the Visual and Infrared Mapping Spectrometer (VIMS) of the Cassini orbiter. The view was released on December 14, 2010. The artificial globe is composed of several radar swaths. The white arrow indicates the region of Sotra Facula, a potential cryo-volcano identified on Titan. The area of Sotra Facula can be found at about 15 degrees south latitude and 40 degrees west longitude. Image credit: NASA/JPL-Caltech/ASI/USGS/University of Arizona.
April 23, 2019 : A New Study Suggests That The Cold Stratospheric Polar Vortices On Titan May Last 22 Earth Years Or 3 Titanian Seasons
A new study entitled « Seasonal Evolution of Titan's Stratosphere During the Cassini Mission », recently published in AGU's journal Geophysical Research Letters and led by Nick Teanby who is a planetary scientist at the University of Bristol in the United Kingdom, reveals that the polar vortices observed on Saturn's largest moon Titan may last 22 Earth years or 3 Titanian seasons. During the long Cassini mission, a giant ethane cloud engulfing the north polar region had been clearly observed during the Winter season in the northern hemisphere and a vortex or a cyclone developing over the south polar region during the Autumn season in the southern hemisphere had been clearly identified as well. The new analyses based on data acquired from the Cassini orbiter and on atmospheric science developed on our planet to understand the logic of seasonal changes on the Opaque Moon reveal the cooling effects of trace gases found in the high-altitude polar vortices. A parallel can be drawn between the polar vortices of Titan and the polar vortices of our planet even if the environmental temperature of the Hazy Moon is much lower than that of the Earth.
Titan's atmosphere is particularly complex with its haze and its hydrological cycle dominated by methane. There are lakes, seas, rivers, evaporation processes, condensation processes and precipitation processes on the giant moon of Saturn. The stratosphere of the Orange Moon which evolves above the troposphere is composed of cooler layers in its lower part and of warmer layers in its upper part. The polar vortices of that enigmatic world can be found in the stratosphere. Those systems of cold air evolving above the polar area clearly appear during the Winter season. The particularly cold environment that can take shape in North America during the Winter season is due to that type of atmospheric system. On the Blue Planet, the vortex tends to dissipate in the Spring season. However, on Saturn's largest moon, the polar vortex identified during the Winter season of the northern hemisphere was still present at the time of the Summer Solstice in the northern hemisphere. Therefore, one can conclude that the vortex may last around 22 Earth years or 3 Titanian seasons.
The image above reveals the high-altitude vortex located over the south polar region of Saturn's largest moon Titan during the Autumn season in the southern hemisphere. That vortex was expected to continue to develop at the time of the observation. The view was obtained on August 31, 2012 with the Narrow-Angle Camera of the Cassini spacecraft on the basis of a spectral filter sensitive to wavelengths of near-infrared radiation centered at 938 nanometers. Image credit: NASA/JPL-Caltech/Space Science Institute.
April 16, 2019 : Some New Analyses Reveal Small And Remarkably Deep Lakes Rich In Methane On Top Of Hills As Well As Lakes Which May Have Evaporated In The North Polar Region Of Titan During The Cassini Mission
Two new studies published in Nature Astronomy on April 15, 2019 unveil new clues or conclusions regarding the structure, the nature or the dynamics of the lakes of Saturn's largest moon Titan. The first study entitled « Deep and methane-rich lakes on Titan » and led by Marco Mastrogiuseppe, who is a Cassini radar scientist at Caltech in Pasadena, California, reveals the identification of deep lakes rich in methane on top of hills in the high latitudes of the northern hemisphere of the Opaque Moon. The second study entitled « The case for seasonal surface changes at Titan's lake district » and led by Shannon MacKenzie, who is a planetary scientist at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, reveals the identification of lakes which may have evaporated during the Cassini mission in the north polar region of that enigmatic moon. The research work was partly based on data obtained during the final close flyby of Saturn's largest moon performed by the Cassini orbiter on April 22, 2017. During that flyby, we obtained radar data unveiling the small lakes of hydrocarbons found in the northern hemisphere.
The new analyses reveal or confirm that the small lakes identified on top of hills in the high latitudes of the northern hemisphere are remarkably deep and are composed of methane. The small pools of hydrocarbons studied by the planetologists can be more than 300 feet or 100 meters deep. Thanks to these analyses, researchers are in a position to have a better understanding of the dynamics of Titan's lakes and of the hydrological cycle of the Hazy Moon. The new clues allow scientists to better analyze the processes of evaporation, condensation and precipitation as well as the way the exotic liquid seeps into the soil. Researchers can draw a parallel between the hydrology of Titan and the hydrology of our planet even if the hydrology of Titan is mainly based on methane whereas the hydrology of the Earth is based on water. In fact, to our knowledge, the Earth and Titan are the only worlds in the Solar System containing stable pools of liquid on their surface. Cyclones, cloud systems and rainfall can take shape on Titan like on Earth. The key molecules of the hydrological cycle of Titan appear to be methane and ethane which can appear in their liquid form on the surface.
The image above reveals a near-infrared view of the disk of Titan unveiling, in particular, the land of lakes in the north polar region of Saturn's largest moon. The view was obtained with the Narrow-Angle Camera of the Cassini orbiter on June 9, 2017. At the time of the observation, the northern hemisphere of the Orange Moon was experiencing the start of the Summer season whereas the southern hemisphere was experiencing the start of the Winter season. The Solstice which leads to the beginning of the Winter season in the southern hemisphere and to the beginning of the Summer season in the northern hemisphere had occurred on May 24, 2017. A Titanian season is particularly long since it represents about 7 Terrestrial years and a Titanian year represents almost 30 Terrestrial years. Image credit: NASA/JPL-Caltech/Space Science Institute.
April 2, 2019 : Is The Likelihood Of A Subsurface Ocean Higher On Enceladus Than On Mimas, Tethys, Dione, Rhea Or Titan ?
Planetologists believe that many worlds in the Solar System may harbor a subsurface ocean rich in liquid water. Around the Gas Giant Jupiter for instance, Europa and Ganymede may contain an ocean beneath their icy crust. The icy moons of the Ringed Planet Saturn may also contain an internal ocean. The tiny moon Enceladus where geysers or water plumes have been clearly identified during the Cassini mission appears to be the perfect candidate in the list of worlds or moons which may harbor a subsurface ocean rich in liquid water. The other icy moons of Saturn such as Tethys, Dione and Rhea may also contain a subsurface ocean even if its potential presence is harder to demonstrate than for the case of Enceladus. Titan which is the largest moon of Saturn and which contains lakes and seas of hydrocarbons on its surface is part of the list of worlds which may harbor a layer of liquid water beneath their external crust. Beyond Saturn, Triton, the largest moon of Neptune, Pluto, the largest Dwarf Planet in the Solar System and its main moon Charon may also contain a subsurface ocean dominated by liquid water.
A new study entitled « Evolution of Saturn's mid-sized moons », recently published online in the journal Nature Astronomy and proposed by Marc Neveu and Alyssa R. Rhoden, reveals numerical simulations regarding the evolution of the geology and the orbit of several moons of Saturn for 4.5 billion years. In this study, the researchers focused their attention on Mimas, Enceladus, Tethys, Dione and Rhea. The moons undergo the influence of the gravity of Saturn and the other moons. The planetologists advanced that the interior of Enceladus, Dione and Tethys must be active thanks to tidal forces or gravitational phenomena. They pointed out however that Mimas may be inactive today even if it undergoes strong tidal forces related to its particularly high proximity to Saturn. They believe that Mimas must have formed relatively recently, between 0.1 and 1 billion years ago. The icy moons studied by Marc Neveu and Alyssa R. Rhoden are located between Saturn and Titan which are the most massive bodies of the system. The simulations bring major clues regarding the surprising difference between Enceladus which is remarkably active and Mimas which seems to be a dead world.
The image above reveals the largest moons of Saturn at scale. From the left part of the view to the right part of the view, one can observe Mimas, Enceladus, Tethys, Dione, Rhea, Titan and Iapetus. Mimas is the closest moon to the Gas Giant whereas Iapetus is the farthest moon to the Ringed Planet. The moons are represented in an order of distance to Saturn from the left part of the view to the right part of the view. The dichotomy between Mimas and Enceladus in terms of geological activity draws the attention of researchers. Enceladus unveils geysers and fractures in its south polar region. The tiny moon may contain a subsurface ocean. By contrast, Mimas seems completely inactive. Credit for the original image of Mimas, Enceladus, Tethys, Dione and Rhea: NASA/JPL-Caltech/Space Science Institute; Credit for the original infrared view of Titan: NASA/JPL-Caltech/University of Nantes/University of Arizona; Credit for the original view of Iapetus: NASA/JPL/Space Science Institute; Credit for the montage: Marc Lafferre, 2019.
January 24, 2019 : A New Study Suggests That The Presence Of A Thick Atmosphere On Titan May Be Intimately Related To The Heating Of Organic Molecules In The Interior Of The Giant Moon
A new research work entitled « Contributions from Accreted Organics to Titan's Atmosphere: New Insights from Cometary and Chondritic Data », released online in The Astrophysical Journal on January 22, 2019 and led by the Doctor Kelly Miller who is a research scientist in SwRI's Space Science and Engineering Division, reveals that the presence of a thick atmosphere on Saturn's largest moon may be closely related to the heating of organics in the interior of the Hazy Moon. Researchers are really fascinated by the thick, dense or deep atmosphere of Titan because most moons in the Solar System are devoid of any significant atmosphere. The other moons of Saturn are devoid of any significant atmosphere and are generally heavily cratered. The gravity of Titan is much weaker than that of the Earth but the air on the surface of the Opaque Moon is much denser than that of the Earth at sea level. In other words, the atmospheric pressure on the surface of Titan is much higher than that of the Earth at sea level. The Titanian atmosphere appears to be largely dominated by molecular nitrogen today.
The team of Kelly Miller advances that there may be an outgassing process involving organics from Titan's interior which fuels, sustains or maintains Titan's atmosphere. The secrets of Titan's atmosphere may be found in the heating or « cooking » of organic material inside the giant moon of the Gas Giant Saturn. During the Cassini mission in the Saturn System, we have had the opportunity to realize that Titan is rich in hydrocarbons or organics. The concentration of methane in Titan's atmosphere can reach about 5 percent at the level of the surface. There are lakes, seas and rivers of hydrocarbons, dominated by methane and ethane, in the polar areas or in the high latitudes of the Opaque Moon. Kelly Miller pointed out : « Titan is a very interesting moon because it has this very thick atmosphere, which makes it unique among moons in our solar system. » She added : « It is also the only body in the solar system, other than Earth, that has large quantities of liquid on the surface. Titan, however, has liquid hydrocarbons instead of water. A lot of organic chemistry is no doubt happening on Titan, so it's an undeniable source of curiosity. » Due to the harsh environment, water can only appear in its solid form on the surface of Titan.
The image above reveals a portion of the Gas Giant Saturn as well as the disk of its largest moon Titan approaching the Gas Giant. One can notice in particular the sharp contrast between the color of Titan's atmosphere, dominated by nitrogen and methane, and the color of Saturn's atmosphere, dominated by hydrogen and helium. This natural color view was generated on the basis of several images taken on January 29, 2008 with the Narrow-Angle Camera of the Cassini spacecraft using red, green and blue spectral filters. The views were captured at a distance of about 2.3 million kilometers or 1.4 million miles from the Opaque Moon. Planetologists try to determine whether the presence of the massive atmosphere of Titan might be related to the release of gases from the interior of the giant moon where heating processes may be encountered. Image credit: NASA/JPL/Space Science Institute.
January 17, 2019 : Researchers Identify Clues Or Evidence Of Rainfall And Changing Seasons In The North Polar Region Of Titan
A new study entitled « Observational evidence for summer rainfall at Titan's north pole », accepted for a release in Geophysical Research Letters, a journal of the American Geophysical Union, and produced by a team of researchers led by Rajani Dhingra, a doctoral student in physics at the University of Idaho in Moscow, reveals clues or evidence of rainfall and changing seasons in the north polar region of the Opaque Moon Titan, on the basis of data acquired from the Cassini orbiter. The planetologists based their analyses on a particular image obtained with the Visual and Infrared Mapping Spectrometer (VIMS) of the Cassini spacecraft which can see in the infrared or near-infrared spectrum. Surface features on Titan can't be observed in the visible spectrum from outer space but with an infrared eye or a near-infrared eye, one can see through the hazy atmosphere of Titan and one can discern surface features such as lakes, seas, volcanoes, mountains or craters.
The team of Rajani Dhingra clearly identified a reflective feature close to the north pole of Saturn's largest moon in a view acquired on June 7, 2016 with the Visual and Infrared Mapping Spectrometer of the Cassini orbiter. The reflective feature could be identified in the infrared or near-infrared spectrum, in a wavelength which allows researchers and the general public to discern landscape features and which brings an idea regarding the composition or the dynamics of the surface. The reflective feature represented, in surface area, about 46,332 square miles which represents, in surface area, approximately 119,999 square kilometers. That is the equivalent of the surface area of a square whose side is about 215 miles long or 346 kilometers long. In fact, the area of the reflective surface represents, roughly, half the size of the Great Lakes. That reflective feature didn't appear to be a permanent feature since it had not been observed in previous images of the area. Moreover, subsequent views of the region, taken from the Cassini spacecraft, didn't show the reflective feature anymore. As a result, that bright or reflective feature appeared to be transient.
The image above reveals a portion of the Titanian disk generated on the basis of data obtained with the Visual and Infrared Mapping Spectrometer (VIMS) of the Cassini orbiter. The lower view shows an enlarged view of the area corresponding to the area of the blue box and of the orange box displayed in the upper view. One can notice the « wet sidewalk », ephemeral region likely representing the outcome of a past rainfall event and likely representing the sign of changing seasons. One can also notice several specular reflections as well as clouds. The mirror-like reflection of a pool of liquids known as Xolotlan Lacus can be identified. In the left part of the lower view, the famous sea called Kraken Mare can be discerned as well. The north pole of the Orange Moon is indicated by a black dot in the lower view. Image credit: NASA/JPL/University of Arizona/University of Idaho.
January 14, 2019 : A New Study Suggests That The Well-Known Moons, Ganymede, Europa, Titan And Enceladus May Not Be Geologically And Biologically Active
A new study led by Paul Byrne, a planetary geologist at North Carolina State University, and recently presented at the annual conference of the American Geophysical Union in Washington, reveals that the well-known moons Ganymede, Europa, Titan and Enceladus may not be geologically and biologically active due to the relatively high thickness and stiffness of their crust. Let's point out, however, that Enceladus which is a tiny moon of the Gas Giant Saturn appears geologically active today but is it enough to allow the presence of a water-based life ? Ganymede and Europa which are moons of Jupiter as well as Titan and Enceladus which orbit around Saturn are believed to harbor a subsurface ocean of liquid water beneath their icy crust. Thanks to the Galileo spacecraft which had evolved inside the system of Jupiter and thanks to the Cassini spacecraft which had studied the system of the Ringed Planet Saturn, we have gathered clues regarding the potential presence of liquid water beneath the crust of several moons of those Gas Giants.
The gravitational influence of the Gas Giants and of the other moons must play a key role in the dynamics of the internal activity of those moons studied by the team of Paul Byrne. The planets engender tidal forces like the tidal forces between the Earth and the Moon. There must be a lot of heat or energy inside those moons. During the previous century, we have sent robots, drones or submarines to explore the abyss of the ocean and we have realized that microorganisms or more complex animals can thrive in the hot springs or in the active volcanoes. Those hot springs shelter ecosystems that appear in a stable state thanks to chemosynthesis, in darkness, in the absence or quasi absence of solar radiations. As a result, can we find microbes or exotic organisms in the subsurface oceans that are believed to exist in the Outer Solar System ? The new work performed by Paul Byrne explores the dynamics of the outer crust of several moons and leads to the conclusion that those moons may not be active inside due to the relatively high stiffness and due to the relatively high thickness of the crust.
The image above reveals the Earth, Ganymede and Europa, which are moons of the Gas Giant Jupiter, and Titan and Enceladus, which are moons of the Ringed Planet Saturn, at scale. The external crust of those moons may be too thick or too strong to allow the emergence or the development of an active geology or biology beneath their presumed icy crust. But the debate regarding the internal structure of moons in the Outer Solar System is far from being over. Credit for the original view of the Earth: DSCOVR, December 25, 2018. Source of the original view of Ganymede: Wikipedia. Source of the original view of Europa: Wikipedia. Source of the original view of Titan: Wikipedia. Credit for the original view of Enceladus: NASA/JPL-Caltech/Space Science Institute. Montage credit: Marc Lafferre, 2019.
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