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Images from NASA’s Cassini spacecraft show a concentration of high-altitude haze and a vortex materializing at the south pole of Saturn’s moon Titan, signs that the seasons are turning on Saturn’s largest moon.Click to play embedded YouTube video.Titan's South Polar Vortex in Motion
Credit: NASA/JPL-Caltech/Space Science Institute
"The structure inside the vortex is reminiscent of the open cellular convection that is often seen over Earth's oceans,” said Tony Del Genio, a Cassini team member at NASA's Goddard Institute for Space Studies, N.Y. “But unlike on Earth, where such layers are just above the surface, this one is at very high altitude, maybe a response of Titan's stratosphere to seasonal cooling as southern winter approaches. But so soon in the game, we’re not sure."
Cassini first saw a “hood” of high-altitude haze and a vortex, which is a mass of swirling gas around the pole in the moon’s atmosphere, at Titan’s north pole when the spacecraft first arrived in the Saturn system in 2004. At the time, it was northern winter. Multiple instruments have been keeping an eye on the Titan atmosphere above the south pole for signs of the coming southern winter.
While the northern hood has remained, the circulation in the upper atmosphere has been moving from the illuminated north pole to the cooling south pole. This movement appears to be causing downwellings over the south pole and the formation of high-altitude haze and a vortex.
Cassini’s visible light cameras saw the first signs of hazes starting to concentrate over Titan’s south pole in March, and the spacecraft’s visual and infrared mapping spectrometer (VIMS) obtained false-color images on May 22 and June 7.
"VIMS has seen a concentration of aerosols forming about 200 miles [300 kilometers] above the surface of Titan's south pole," said Christophe Sotin, a VIMS team member at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "We've never seen aerosols here at this level before, so we know this is something new."
During a June 27 distant flyby, Cassini’s imaging cameras captured a crow’s-eye view of the south polar vortex in visible light. These new images show this detached, high-altitude haze layer in stunning new detail.
"Future observations of this feature will provide good tests of dynamical models of the Titan circulation, chemistry, cloud and aerosol processes in the upper atmosphere,” said Bob West, deputy imaging team lead at JPL.
Titan's Swirling South Polar Vortex
This reads like they are stating that the massive collection of swirling gas measures 3200 miles across but this is the size of Titan. Does anyone know the actual size of the vortex?
http://en.wikipedia.org/wiki/Climate_of_Titan wrote: <<Titan's atmosphere circulates in a single enormous Hadley cell. Warm air rises in Titan's southern hemisphere—which was experiencing summer during Huygens' descent—and sinks in the northern hemisphere, resulting in high-altitude air flow from south to north and low-altitude airflow from north to south. Such a large Hadley cell is only possible on a slowly rotating world such as Titan [15.945 days synchronous rotation]. The pole-to-pole wind circulation cell appears to be centered on the stratosphere; simulations suggest it ought to change every twelve years, with a three-year transition period, over the course of Titan's year (30 terrestrial years). This cell creates a global band of low pressure—what is in effect a variation of Earth's Intertropical Convergence Zone (ITCZ). Unlike on Earth, however, where the oceans confine the ITCZ to the tropics, on Titan, the zone wanders from one pole to the other, taking methane rainclouds with it. This means that Titan, despite its frigid temperatures, can be said to have a tropical climate.
The number of methane lakes visible near Titan's southern pole is decidedly smaller than the number observed near the north pole. As the south pole is currently in summer and the north in winter, an emerging hypothesis is that methane rains onto the poles in winter and evaporates in summer.
In June 2012, Cassini imaged a rotating vortex on Titan's southern pole, which the imaging team believe is related to a "polar hood" - an area of dense, high altitude haze seen over the northern pole since the probe's arrival in 2004. As the hemispheres are now switching seasons since the 2009 equinox, with the southern pole entering winter and the north entering summer, it is hypothesised that this vortex could mark the formation of a new, southern polar hood.
In September 2006, Cassini imaged a large cloud at a height of 40 km over Titan's north pole. Although methane is known to condense in Titan's atmosphere, the cloud was more likely to be ethane, as the detected size of the particles was only 1–3 micrometers and ethane can also freeze at these altitudes. In December, Cassini again observed cloud cover and detected methane, ethane and other organics. The [north pole] cloud was over 2400 km in diameter and was still visible during a following flyby a month later. One hypothesis is that it is currently raining (or, if cool enough, snowing) on the north pole; the downdrafts at high northern latitudes are strong enough to drive organic particles towards the surface. These were the strongest evidence yet for the long-hypothesized "methanological" cycle (analogous to Earth's hydrological cycle).
Clouds have also been found over the south polar region. While typically covering 1% of Titan's disk, outburst events have been observed in which the cloud cover rapidly expands to as much as 8%. One hypothesis asserts that the southern clouds are formed when heightened levels of sunlight during the Titanian summer generate uplift in the atmosphere, resulting in convection. This explanation is complicated by the fact that cloud formation has been observed not only post–summer solstice but also at mid-spring. Increased methane humidity at the south pole possibly contributes to the rapid increases in cloud size. There had been summer in Titan's southern hemisphere until 2010, when Saturn's orbit, which governs the moon's motion, tilted the northern hemisphere towards the Sun. When the seasons switch, it is expected that ethane will begin to condense over the south pole.
Research models that match well with observations suggest that clouds on Titan cluster at preferred coordinates and that cloud cover varies by distance from the surface on different parts of the satellite. In the polar regions (above 60 degrees latitude), widespread and permanent ethane clouds appear in and above the troposphere; at lower latitudes, mainly methane clouds are found between 15 and 18 km, and are more sporadic and localized. In the summer hemisphere, frequent, thick but sporadic methane clouds seem to cluster around 40°.
Ground-based observations also reveal seasonal variations in cloud cover. Over the course of Saturn's 30-year orbit, Titan's cloud systems appear to manifest for 25 years, and then fade for four to five years before reappearing again.
Cassini has also detected high-altitude, white, cirrus-type clouds in Titan's upper atmosphere, likely formed of methane.
Although no evidence of lightning activity has yet been observed on Titan, computer models suggest that clouds in the moon's lower troposphere can accumulate enough charge to generate lightning from an altitude of roughly 20 km.>>
May be you can estimate it from this image by Jason Major.BMAONE23 wrote:Does anyone know the actual size of the vortex?
orin stepanek wrote:
looks like Titan is having a hurricane!
http://en.wikipedia.org/wiki/Polar_vortex wrote:
<<A polar vortex is a persistent, large-scale cyclone located near one or both of a planet's geographical poles. On Earth, the polar vortices are located in the middle and upper troposphere and the stratosphere. These cold-core low-pressure areas strengthen in the winter and weaken in the summer. They usually span [8% to 15% the diameter of the Earth] in which the air is circulating in [the direction the Earth rotates]. The reason for the rotation is the same as any other cyclone, the Coriolis effect. Other astronomical bodies are also known to have polar vortices, including Venus, Mars, Jupiter, Saturn and Saturn's moon Titan.>>
Thanks Bystander,bystander wrote:May be you can estimate it from this image by Jason Major.BMAONE23 wrote:Does anyone know the actual size of the vortex?
