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'[TECH]:: NASA confirms liquid lake on surface of T'
2008\07\30@234901 by Apptech

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Since the availability fo data from the Cassini probe
several years ago people have thought that numerous dark
surface features on Titan's surface were liquid lakes. NASA
has decided that based on data acquired early this year, now
is the time to announce that they conclude the assumptions
are correct. (Ethane has been detected by spectroscopy.)

As one such lake is about as large as Lake Ontario (so now
named "Ontario Lacus ") and is believed to be filled with
liquid Ethane and Methane it may, one day, prove 'quite
useful'. (Atmosphere is ~ 95% Nitrogen with a Methane liquid
cycle and Ethane is formed from sunlight decomposition of
Methane

AFAIK the latest July 31st report in nature is based on a
flyby analysis in about January this year.

       http://www.nasa.gov/home/hqnews/2008/jul/HQ_08_193_Titan_lake.html

Surface temperature is 'a bit cold' at round -100 degrees
Celsius



           Russell McMahon


___________________________________


NASA Confirms Liquid Lake On Saturn Moon


PASADENA, Calif. -- NASA scientists have concluded that at
least one of the large lakes observed on Saturn's moon Titan
contains liquid hydrocarbons, and have positively identified
the presence of ethane. This makes Titan the only body in
our solar system beyond Earth known to have liquid on its
surface.

Scientists made the discovery using data from an instrument
aboard the Cassini spacecraft. The instrument identified
chemically different materials based on the way they absorb
and reflect infrared light. Before Cassini, scientists
thought Titan would have global oceans of methane, ethane
and other light hydrocarbons. More than 40 close flybys of
Titan by Cassini show no such global oceans exist, but
hundreds of dark lake-like features are present. Until now,
it was not known whether these features were liquid or
simply dark, solid material.

"This is the first observation that really pins down that
Titan has a surface lake filled with liquid," said Bob Brown
of the University of Arizona, Tucson. Brown is the team
leader of Cassini's visual and mapping instrument. The
results will be published in the July 31 issue of the
journal Nature.

Ethane and several other simple hydrocarbons have been
identified in Titan's atmosphere, which consists of 95
percent nitrogen, with methane making up the other 5
percent. Ethane and other hydrocarbons are products from
atmospheric chemistry caused by the breakdown of methane by
sunlight.

Some of the hydrocarbons react further and form fine aerosol
particles. All of these things in Titan's atmosphere make
detecting and identifying materials on the surface
difficult, because these particles form a ubiquitous
hydrocarbon haze that hinders the view. Liquid ethane was
identified using a technique that removed the interference
from the atmospheric hydrocarbons.

The visual and mapping instrument observed a lake, Ontario
Lacus, in Titan's south polar region during a close Cassini
flyby in December 2007. The lake is roughly 7,800 square
miles in area, slightly larger than North America's Lake
Ontario.

"Detection of liquid ethane confirms a long-held idea that
lakes and seas filled with methane and ethane exist on
Titan," said Larry Soderblom, a Cassini interdisciplinary
scientist with the U.S. Geological Survey in Flagstaff,
Ariz. "The fact we could detect the ethane spectral
signatures of the lake even when it was so dimly
illuminated, and at a slanted viewing path through Titan's
atmosphere, raises expectations for exciting future lake
discoveries by our instrument."

The ethane is in a liquid solution with methane, other
hydrocarbons and nitrogen. At Titan's surface temperatures,
approximately 300 degrees Fahrenheit below zero, these
substances can exist as both liquid and gas. Titan shows
overwhelming evidence of evaporation, rain, and fluid-carved
channels draining into what, in this case, is a liquid
hydrocarbon lake.

Earth has a hydrological cycle based on water and Titan has
a cycle based on methane. Scientists ruled out the presence
of water ice, ammonia, ammonia hydrate and carbon dioxide in
Ontario Lacus. The observations also suggest the lake is
evaporating. It is ringed by a dark beach, where the black
lake merges with the bright shoreline. Cassini also observed
a shelf and beach being exposed as the lake evaporates.

"During the next few years, the vast array of lakes and seas
on Titan's north pole mapped with Cassini's radar instrument
will emerge from polar darkness into sunlight, giving the
infrared instrument rich opportunities to watch for seasonal
changes of Titan's lakes," Soderblom said.

Launched in Oct. 1997, Cassini's 12 instruments have
returned a daily stream of data from Saturn's system. The
mission is a cooperative project of NASA, the European Space
Agency and the Italian Space Agency.

For information on Cassini, visit:

2008\07\31@014059 by Sean Breheny

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Hi Russell,

Out of curiosity, I worked out how long the world's present energy
consumption could be supplied by such a lake:

Volume of Lake Ontario=393 cubic miles=1.6e12 cubic meters
Assume for simplicity's sake it is pure liquid methane. Then the
density would be about 422kg/m^3
You can get as much as 50MJ per kg from methane combustion, although I
used half of this considering the need to warm it up and the max
efficiency of a thermal engine: 25MJ/kg

The world present energy use per year is about 5e20 J (as of 2005).

(1.6e12*422*25e6)/5e20=33.76 years

At this rate, the lake would last 34 years. Not all that long!

Then again, this side-steps all the trouble which you would have to
take in order to transport it back to Earth (unless you were thinking
of some ways to use it out in space, such as fuel for a spacecraft or
a settlement on a planet).

Sean


On Wed, Jul 30, 2008 at 11:47 PM, Apptech <spam_OUTapptechTakeThisOuTspamparadise.net.nz> wrote:
> As one such lake is about as large as Lake Ontario (so now
> named "Ontario Lacus ") and is believed to be filled with
> liquid Ethane and Methane it may, one day, prove 'quite
> useful'. (Atmosphere is ~ 95% Nitrogen with a Methane liquid
> cycle and Ethane is formed from sunlight decomposition of
> Methane
>

2008\07\31@015600 by Apptech

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> Out of curiosity, I worked out how long the world's
> present energy
> consumption could be supplied by such a lake:

> At this rate, the lake would last 34 years. Not all that
> long!


That's just the largest lake that they are aware of. They
are scattered all over the planets surface AFAIK. After all,
it rains Methane there :-).


       Russell

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