February 23, 2023: A New Study Reveals That The Liquid Motion In The Presumed Subsurface Ocean Of Titan Is Influenced By The Deformation Of The Ice Shell
A new research work entitled "A numerical study of the liquid motion in Titan's subsurface ocean", published in Icarus in the volume 388 of December 2022 and proposed by a team involving David Vincent reveals the influence of the tidal forces and of the deformation of the external crust upon the dynamics of the presumed subsurface ocean likely dominated by liquid water on Titan. The largest moon of the Gas Giant Saturn is part of those worlds of the Solar System that may contain a subsurface ocean rich in liquid water. The small and bright moon Enceladus unveils geysers or eruptions revealing water ice and organics in its south polar region suggesting the presence of a subsurface ocean beneath the external crust dominated by water ice. The other major moons of Saturn tend to contain significant amounts of water ice. That's the case for Tethys, Dione or Rhea in particular. Those moons must contain a liquid layer beneath the external crust. That's also the case for other moons or worlds in the Solar System. Europa and Ganymede, two major moons of Jupiter, may contain a subsurface ocean dominated by liquid water. Triton or Charon, for instance, may also contain a subsurface ocean.
The dynamics of the ocean on Earth is influenced by the atmosphere, by tectonics, by volcanism, by solar radiations or by tidal phenomena related to the Moon in particular. On worlds where the ocean is found beneath the external crust, the logic is different. Tidal forces will tend to deform the external crust and the deformation will tend to influence the dynamics of the internal ocean. Researchers must resort to simulations or models in order to anticipate the potential dynamics of the internal ocean. The currents will be influenced by various phenomena such as the tidal forcing, the deformation of the external crust dominated by water ice and the temperature gradient related to the surface and bottom heat fluxes. Planetologists can simulate the flow engendered by the tidal forces and by the deformation of the external icy crust on the basis of a 2D depth-averaged model. The temperature gradient related to the surface and bottom heat fluxes produces horizontal and vertical density variations whose effects can only be evaluated by a 3D baroclinic model. Does the core radiate energy ? How is the energy from the Sun diffused toward the presumed internal ocean ? Many factors or parameters must be considered.
The image in the upper part of this table represents a raw view of a portion of Titan obtained from the Cassini orbiter on February 12, 2015 on the basis of the CB3 filter and of the CL2 filter. The view whose file name is W00091654.jpg had not been validated or calibrated at the time of the observation and a validated or calibrated version of the original image was going to be archived with the Planetary Data System proposed by NASA. One can clearly notice the remarkable contrast between relatively dark areas and relatively bright areas. The image in the lower part of this table represents a colorized version of the original view. Credit for the original image: NASA/JPL-Caltech/Space Science Institute. Credit for the colorization process of the original image: Marc Lafferre, 2023.
February 4, 2023: An Ancient Titan Composed Of Hydrocarbon Oceans And Continents Simulated By A Global Climate Model
A new study entitled "Paleoclimate of Titan with hydrocarbon oceans and continents simulated by a global climate model", proposed by Tetsuya Tokano and published in Icarus in the volume 389 on January 1st, 2023 unveils simulations upon the climate of a potential ancient Titan composed of oceans of hydrocarbons and composed of continents. The paleoclimate of Titan simulated by the planetologist Tetsuya Tokano represents a potential climate of Saturn's largest moon one gigayear ago that is to say one billion years ago. Titan may have contained oceans of hydrocarbons as well as continents at that time. Several configurations are envisaged in the simulations of the ancient climate of Titan. The composition of the ocean can be dominated by methane or the composition of the ocean can be dominated by ethane. The simulations produced via a global climate model with a slab ocean model take into account the composition of the ocean as well as the potential presence of continents or the potential absence of any continent. The key molecules of the potential ancient oceans appear to be methane (CH4) and ethane (C2H6).
Today, the climate of Titan is really harsh due to the relatively low level of energy received from the Sun. The environmental temperature of Titan at the level of the surface is around -179 degrees Celsius, -290 degrees Fahrenheit or 94 Kelvin so that methane, ethane or even propane can appear in their liquid form on the surface. The atmosphere of Titan is currently dominated by molecular nitrogen like our own atmosphere but the second most abundant gas of the atmosphere is not oxygen on Titan. The second most abundant gas of the atmosphere of the giant moon is in fact methane. Methane can form lakes, rivers or seas on Titan. That's also the case for ethane, a molecule that is heavier than methane. The climate of Titan will be intimately linked to the size of the oceans or seas and to the composition of the oceans or seas. What will the climate be if the ocean is dominated by methane ? What will the climate be if the ocean is dominated by ethane ? The study of Tetsuya Tokano reveals that the climate over oceans rich in ethane is dry in terms of methane. The study also suggests that the climate over oceans rich in ethane is windier than the climate over oceans rich in methane.
The image in the upper part of the table represents a view of Titan obtained on May 22, 2012 from the Cassini orbiter. The file name of the image is W00074169.jpg. The view was acquired on the basis of the CB3 filter and of the CL2 filter. The image had not been validated or calibrated at the time of the observation and a validated or calibrated version 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 notice, in particular, surface features with relatively bright and relatively dark areas which tend to be dominated by linear and parallel dunes extending over long distances in the low or middle latitudes. Credit for the original view: NASA/JPL-Caltech/Space Science Institute. Credit for the colorization process of the original view: Marc Lafferre, 2023.