Views from Cassini at Saturn
Intense, lovely, surreal. Asteroids, moons and stars shift through the footage of our cosmic void around Saturn. Music by NIN.
No one has ever floated a boat on another world, but NASA is now considering doing just that, on Saturn’s icy moon Titan. Probing the moon’s hydrocarbon lakes could reveal clues to its climate and perhaps even signs of exotic life forms.
Titan’s surface is dotted with lakes, making it strangely reminiscent of Earth. But rather than water, the lakes are filled with a mixture of methane and ethane, which are gases on Earth but are liquid at Titan’s surface temperature of -180 °C.
NASA is now considering sending a probe to splash down into one of the lakes. It has selected a mission called the Titan Mare Explorer (TiME) as one of three finalists competing for a chance to fly in 2016. The TiME project is led by Ellen Stofan of Proxemy Research in Gaithersburg, Maryland.
In 2023, after a seven-year cruise from Earth, TiME would parachute into a lake in Titan’s northern hemisphere called Ligeia Mare. Powered by heat from the decay of an onboard plutonium supply, the probe would bob around the lake’s surface and make measurements for about three months.
Titan is the only place in the solar system that appears to have a cycle analogous to the water cycle on Earth, with hydrocarbon rain depositing liquid on the surface, followed by evaporation and more rain.
TiME would help reveal details about this cycle by measuring the temperature, humidity and winds at the surface of the lake. With luck, it could be the first probe to experience rain on another world. The probe would also snap pictures of the lake’s surface and shorelines and peer up at clouds in the sky.
Though it lacks a means of propulsion, the flying-saucer shaped probe should gradually drift with the breeze, allowing it to sample different parts of the lake. As it did so, it could measure the lake’s depth with sonar and taste the brew of chemicals it contains with a mass spectrometer.
That would provide a new window into Titan’s intriguing chemistry. Complex carbon-based, or organic, molecules, such as acetylene, are known to form in abundance in the moon’s atmosphere and rain down onto the surface.
The organic molecules are likely to get mixed into the lakes and might undergo further chemical reactions there. Some scientists have even speculated that microscopic life forms could live in the lakes, eating acetylene and breathing hydrogen gas.
With its mass spectrometer, TiME would explore any interesting chemistry going on in the lake. If any life is present, it might produce unusual patterns in the abundance of organic molecules.
“Titan is an endpoint on exploring what are the limits to life in our solar system,” Stofan told New Scientist. “We’re going to be looking for patterns in abundances of compounds to look for evidence for more complex or interesting reactions.”
But in order to fly, TiME will have to out-compete two other proposed missions: a seismic monitoring station for Mars and a probe that would hop around the surface of a comet.
NASA has awarded $3 million to each of the three competing teams to flesh out their mission concepts. After a review in 2012, the agency plans to decide which mission will receive the $425 million it needs to fly.
Watch Cassini approach Saturn through its own eyes from the 2004 journey. Thousands of photos have been stitched together seamlessly with music which will become part of the IMAX feature, Outside In.
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Prometheus Creating Saturn Ring Streamers
What’s causing those strange dark streaks in the rings of Saturn? Prometheus. Specifically, an orbital dance involving Saturn’s moon Prometheus keeps creating unusual light and dark streamers in the F-Ringof Saturn. Now Prometheus orbits Saturn just inside the thin F-ring, but ventures into its inner edge about every 15 hours. Prometheus’ gravity then pulls the closest ring particles toward the 80-km moon. The result is not only a stream of bright ring particles but also a dark ribbon where ring particles used to be.
Fluid clue to Saturn’s hexagon
An unusual hexagonal structure found in Saturn’s atmosphere has been recreated in an Oxford laboratory to study the ways in which such an unusual polygonal structure may have formed. The mysterious ‘hexagon’ occurs at the planet’s chilly North Pole and, as reported in 2008, has been shown to extend deep into Saturn’s atmosphere with a ‘hotspot’ at its core.
They did this with experiments using a water tank filled with a solution of water and glycerol peppered with white ‘tracer’ particles. This tank was then mounted on a turntable and lit in such a way that the solution’s flow at various speeds could be captured on camera. The video above shows the development of a flow produced when a disk or ring mounted in the base or lid of the tank is set into rotation relative to the rest of the tank.
This differential rotation carries the fluid along with it to create a shear flow in which the azimuthal flow varies with radius. It crudely represents the shear found on the flanks of the eastward-moving jet stream on Saturn at around 76 degrees North, with around the same magnitude of shear compared with the background rotation as on Saturn.
This flow is unstable and spontaneously develops meanders and vortices that eventually form a six-sided pattern that settles into a hexagonal shape - something made clear by the pattern of tracer particles. The formation of such a steady, symmetrical pattern, seems to be directly analogous to what appears to be happening on Saturn on a scale of thousands of kilometres.
The experiments demonstrate that at least one possible end-product of such an instability is the production of a steady, polygonal shape that calculations suggest could also occur on Saturn. While this does not prove that Saturn’s hexagon definitely occurs via the same processes as in this experiments, it does demonstrate that it could do so, and suggests other things for scientists to look for that may help to improve our understanding of Saturn’s atmosphere.Source: University of Oxford