| Subject: Re: Titan |
Author:
Andrzej
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Date Posted: 12:20:06 10/05/03 Sun
In reply to:
blobrana
's message, "Titan" on 11:43:19 04/27/03 Sun
>Scientists have peered through the smoggy orange haze
>of Saturn's largest moon, Titan, and seen icy bedrock
>exposed on the surface.
>
> The observations reveal a surface that is not
>entirely covered by liquid and solid organic materials
>that rain out of the atmosphere, as was thought.
>
>"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," .
>
>Titan will be visited by a probe next year that will
>parachute down to its surface sending back pictures.
>
>
>Titan's atmosphere is about 10 times as massive as
>Earth's and is primarily nitrogen laced with methane
>and ethane.
>
>It forms a dense hydrocarbon haze high in the moon's
>stratosphere as 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.
>
> But what makes Titan's atmosphere almost opaque
>results in a rich chemistry on the surface.
>
>The by-products of methane molecules destroyed in the
>Sun's ultraviolet light react with other molecules in
>Titan's atmosphere, forming organic substances that
>fall onto the moon's surface, blanketing the icy
>bedrock and forming lakes and oceans of hydrocarbons.
>
>University of Arizona planetary scientist Jonathan
>Lunine and others theorise that atmospheric methane is
>replenished on Titan by a liquid cycle similar to
>Earth's hydrologic cycle. Others suggest that Titan's
>methane is produced by geologic activity.
>
>"Assuming that Titan's atmosphere has existed over the
>moon's 4.6 billion year lifetime, 800 metres of
>sediments would lie on the surface," .
>
>"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."
>
>
>
>Looking at Titan through an infrared "windows" of
>light that can reach the surface, or regions between
>the very thick methane bands, the astronomers conclude
>that much of Titan's surface is exposed icy bedrock.
>
>"Titan's spectra resemble Ganymede's spectrum,
>dominated by ice features," .
>
>In 1994 the Hubble Space Telescope obtained its first
>images of Titan's surface, and images from others
>since show that Titan has large patches of darker
>terrain.
>
>"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."
>
>In July 2004 the Cassini spacecraft will arrive at
>Saturn and go into orbit. It will also drop a probe
>onto Titan.
>
>Cassini will also map large chunks of Titan's surface
>at optimal haze-penetrating, near-infrared
>wavelengths.
>
>The research is published in the journal Science.
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