Fog discovered on Saturn’s largest moon Titan

December 19, 2009 By Leave a Comment

Los Angeles, Dec 20 : US scientists have discovered fog moving across the south pole of Saturn’s largest moon, Titan.

Titan looks to be the only place in the solar system aside from Earth to have copious quantities of liquid (largely, liquid methane and ethane) on its surface.

The new discovery suggests that Earth and Titan share yet another feature, which is inextricably linked with that surface liquid: common fog, according to researchers at the California Institute of Technology (Caltech).

The presence of fog provides the first direct evidence for the exchange of material between the surface and the atmosphere, and thus of an active hydrological cycle, which previously had only been known to exist on Earth, the researchers said in a paper published in the latest issue of Astrophysical Journal Letters.

Titan’s south pole is spotted “more or less everywhere” with puddles of methane that give rise to sporadic layers of fog, said planetary astronomer Mike Brown of Caltech, Xinhua reported Saturday.

The researchers made their discovery using data from the Visual and Infrared Mapping Spectrometer (VIMS) onboard the Cassini spacecraft, which has been observing Saturn’s system for the past five years.

The VIMS instrument provides “hyperspectral” imaging, covering a large swath of the visible and infrared spectrum.

Brown and his colleagues searched public online archives to find all Cassini data collected over the moon’s south pole from October 2006 through March 2007. They filtered the data to separate out features occurring at different depths inthe atmosphere, ranging from 20 km to 0.25 km above the surface.

Using other filters, they homed in on “bright” features caused by the scattering of light off small particles — such as the methane droplets present in clouds.

In this way, they isolated clouds located about 750 meters (less than a half-mile) above the ground. These clouds did not extend into the higher altitudes but into the moon’s troposphere, where regular clouds form. In other words, said Brown, they had found fog.

Brown noted that evaporating methane on Titan “means it must have rained, and rain means streams and pools and erosion and geology. The presence of fog on Titan proves, for the first time, that the moon has a currently active methane hydrological cycle”.

The presence of fog also proves that the moon must be dotted with methane pools, Brown said. That’s because any ground-level air, after becoming 100 percent humid and turning into fog, would instantly rise up intothe atmosphere like a giant cumulus cloud.

“The only way to make the fog stick around on the ground is to both add humidity and cool the air just a little,” he explained.(IANS)

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Scientists see storm brewing over Titan’s tropical desert

August 13, 2009 By Leave a Comment

Washington, August 13 (ANI): A new research has discovered significant cloud formation within the tropical zone near the equator of Saturn’s largest moon, Titan, which is evidence that the parched, dry desert of the natural satellite can support large-scale storms.

The evidence comes from a team of US astronomers using the Gemini North telescope and NASA’s Infrared Telescope Facility (IRTF) both on Hawaii’s Mauna Kea.

Titan, the solar system’s second largest moon, has received considerable attention by scientists since NASA’s Cassini mission deployed the Huygens probe that descended through the moon’s atmosphere in January 2005.

During its descent, the probe’s cameras revealed small-scale channels and what appear to be stream beds in the equatorial regions that seemed to contradict atmospheric models predicting extremely dry desert-like conditions near the equator.

Until now, these erosional (fluvial) features have been explained by the possibility of liquid methane seeping out of the ground.

“In April 2008, we observed what was a global event that shows how storm activity in one region can trigger clouds, and probably rainfall, over arid regions, such as the tropics where Huygens landed,” said team member Henry Roe from Lowell Observatory.

Prior to this event (in April 2008), it was not known whether significant cloud formation was possible in Titan’s tropical regions.

This activity in Titan’s tropics and mid-latitudes also seems to have triggered subsequent cloud development at the moon’s south pole where it was considered improbable due to the Sun’s seasonal angle relative to Titan.

“Of course these rain showers are not liquid water like here on Earth, but are instead made of liquid methane. Just like the streambeds and channels that are carved by liquid water on Earth, we see features on Titan that have been created by flowing liquid methane,” Roe added.

The team monitored Titan on 138 nights over 2.2 years and during that time cloud cover was well under one percent.

Then, mid-April of 2008, just after team member Emily Schaller had handed in her doctoral dissertation focusing on Titan’s minimal cloud cover she noticed the dramatic increase in cloud cover.

During this three-week episode, clouds forming at about 30 degrees south latitude were observed, followed several days later by clouds closer to the equator and at the moon’s south pole.

The apparent connection between the cloud formations leads to the possibility that cloud formation in one area of the moon can instigate clouds in other areas by a process known as atmospheric teleconnections. (ANI)

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Titan’s squashed shape hints at vast reserves of liquid methane beneath its surface

April 3, 2009 By Leave a Comment

London, April 3 (ANI): A new study has suggested that Saturn’s moon Titan is surprisingly non-spherical, and is squashed at its poles, suggesting it may hide vast reserves of liquid methane beneath its surface.

Titan is 5150 kilometers across, making it larger than Mercury and only slightly smaller than the largest moon in the solar system, Jupiter’s Ganymede.

According to a report in New Scientist, by bouncing radar signals off the moon’s smog-enshrouded surface, the Cassini spacecraft has now measured Titan’s shape precisely for the first time.

“What we have are the first actual measurements showing that Titan’s not an exact sphere – this distorted egg-shaped thing best fits the observed shape,” study leader Howard Zebker of Stanford University told New Scientist.

Compared to a perfect sphere, Titan is squashed at its poles, with the ground at the poles about 700 meters lower than at the equator.

Titan, which always shows the same face to Saturn, is also stretched out a little in the planet’s direction, so the elevation around the equator itself varies by about 400 meters.

Titan is more squashed than expected, which may be a sign that the moon was once closer to Saturn.

In a closer, faster orbit, Titan also would have spun faster, assuming it had one face locked on Saturn back then as it does today.

An orbit 23 percent closer than the one Titan occupies today would account for the extra squashing at the poles and bulging at the equator.

The lower elevation at the poles fits nicely with one proposed explanation for why Titan’s lakes of hydrocarbons – made of liquid ethane and possibly also liquid methane – are found only in the polar regions.

If Titan has vast stores of hydrocarbons beneath its surface, the lakes could simply be places where the ground lies low enough to expose some of this liquid.

This is similar to the way digging a well shaft on Earth will expose groundwater.

In this scenario, it makes sense that the lakes appear preferentially at the lower-lying poles, according to Stephen Clifford of the Lunar and Planetary Institute in Houston, Texas.

“There’s this potential for liquid to peek above the top of the solid body at the poles,” he said.

If Titan does conceal large reservoirs of methane and ethane beneath its icy surface, it could also explain why methane is so abundant in Titan’s atmosphere. (ANI)

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Slushy water on Titan may be proof of volcanism

March 30, 2009 By Leave a Comment

London, March 30 (ANI): New radar images from NASA’s Cassini probe have suggested that slushy water from a hidden ocean may be pooling onto the icy surface of Saturn’s moon Titan, thus bolstering the case for the existence of volcanoes on its surface.

Titan’s exterior, where the temperature is around -180 degree Celsius, is thought to be mostly water-ice, but it may be a different story deep down.

Variations in the moon’s rate of rotation suggest an ocean could lurk below.

An area of Titan called Hotei Arcus appears to fluctuate in brightness on timescales of several months, and in 2005, Robert Nelson of NASA’s Jet Propulsion Laboratory in Pasadena, California, and colleagues, suggested this might be the result of “cryovolcanic” eruptions of water from below.

Others argued that the flickers were caused by the moon’s hazy atmosphere.

The cryovolcanism idea was bolstered in 2008, when observations of Hotei Arcus by a radar instrument aboard NASA’s Cassini probe revealed structures that resembled lava flows.

Some opponents of the idea still argued these might be deposits of sediment, carried by a flow of methane in the past.

Now, according to a report in New Scientist, radar images from Cassini have allowed scientists led by Randolph Kirk of the US Geological Survey in Flagstaff, Arizona, to create a 3D view of the area.

It turns out that the sinuous structures tower 200 meters above their surroundings.

They say that this is consistent with the structures having formed when slushy water and ammonia squirted onto the surface and froze, but that they could not have been produced by a flood of liquid methane depositing sediment.

The structures may have formed when slushy water and ammonia squirted onto the surface and froze.

If slush volcanoes have been erupting recently, Titan would join a select group of solar system objects – Earth and Io – known to be volcanic at present.

As for life existing in the ocean below, Kirk said, “It’s conceivable life could be going on down there.” (ANI)

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