Other Worlds - the surface of Titan

Greetings,

Sending this news release out for those who are interested in combat
encounters on other worlds. We all have a pretty good idea o the environments
of the moon and Mars, but what about
other worlds - like...Titan? This should let some imaginations
run wild. Alien environments, anyone?  ;-)

Mk
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TITAN REVEALS A SURFACE DOMINATED BY ICY BEDROCK
> From Lori Stiles, UA News Services, 520-621-1877

Scientists who have peered through the smoggy orange haze of Saturn's largest
moon, Titan, have discovered that the surface is not entirely covered by
liquid and solid organic materials that rain out of the atmosphere. Extensive
areas of icy bedrock lie exposed on Titan's surface, they report in today's
issue of Science (April 25, 2003).

"Titan's surface reflectivity looks a lot like that of Jupiter's moon,
Ganymede. This is somewhat surprising because Titan is believed to have a lot
of organic gook on its surface," said Caitlin A. Griffith of the University of
Arizona Lunar and Planetary Laboratory.

______________________
Contact Information Caitlin A. Griffith
520-626-3806
griffith@lpl.arizona.edu
________________________

Titan's atmosphere, ten times as massive as Earth's, is primarily nitrogen
laced with such poisonous substances as methane and ethane. Titan is thickly
veiled by a dense hydrocarbon haze that forms in the high stratosphere as
atmospheric methane is destroyed by sunlight. The haze is much thicker than
Earth's worst city smog. It was impenetrable to cameras aboard the Pioneer and
Voyager spacecraft that flew by the Saturn system in the late 1970s and early
1980s.

The by-products of methane molecules destroyed in the sun's
ultraviolet light react with other molecules in Titan's atmosphere, forming
organic droplets and particulates that fall onto the moon's surface,
blanketing the icy bedrock and forming lakes and oceans. UA planetary
scientist Jonathan Lunine and others theorize that atmospheric methane is
replenished on Titan in a liquid cycle similar to Earth's hydrologic cycle.
Others theorize that Titan's methane is produced by geologic activity.

Scientists have measured and modeled the rate of methane photolysis, and from
that deduced how much material annually settles out of the atmosphere.

"Assuming that Titan's atmosphere has existed over the moon's 4.6 billion year
lifetime, 800 meters of sediments would lie on the surface," she said. "So one
might ask whether the surface is covered with the liquid and the solid
sediments, such that we can't see the ice and rock that exist beneath."

Since 1991, Griffith and others have developed and used a technique that
allows observers to spectroscopically view the surface at several narrow
infrared "windows," or regions between the very thick methane bands. On this
project, the team used the United Kingdom Infrared Telescope and NASA's
Infrared Telescope Facility, both on Mauna Kea,
Hawaii, to observe at eight near-infrared windows.

Griffith, Tobias Owen of Hawaii's Institute for Astronomy, Thomas R. Geballe
of the Gemini Observatory, John Rayner of Hawaii's Institute for Astronomy,
and Pascal Rannou of the Pierre and Marie Curie University in Paris conclude
after analyzing surface reflectivity that much of Titan's surface is exposed
icy bedrock.

"Titan's spectra resemble Ganymede's spectrum, dominated by ice features,"
they report.

Images from UA planetary scientist Peter Smith, who used the Hubble Space
Telescope in 1994 to get the first image of Titan's surface, and images from
others since show that Titan has large patches of darker terrain, Griffith
noted.

"It's not clear what the darker material is, but one possibility is that it is
these organic liquids and sediments. The images, taken together with our
results, suggest that organic stuff is moved around on the surface in such a
way as to expose bedrock ice."

The new findings are indirectly relevant to the NASA/ESA Cassini
mission/Huygens probe to arrive at Saturn in July 2004, Griffith
noted. Scientists would like a better idea of how optically thick Titan's haze
is, and how bright or dark its surface will be, to calculate camera exposure
times. In addition, scientists are fine tuning their questions as they plan
the Cassini observations.

Cassini spacecraft instruments include the Visual and Infrared Mapping
Spectrometer (VIMS), an experiment headed by Robert H. Brown
of the UA Lunar and Planetary Lab. The orbiter-borne instrument will
map large chunks of Titan's surface at optimal haze-penetrating,
near-infrared wavelengths. Griffith is working with the VIMS science
team.