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Posted by Chris on January 5, 2007, 7:13 am
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Carbon + energy = biology, is there any biology on Titan?
> http://www.jpl.nasa.gov/news/features.cfm?feature=1258
>
> Titan Has Liquid Lakes, Scientists Report in Nature
> January 03, 2007
>
> Scientists report definitive evidence of the presence of lakes filled
> with liquid methane on Saturn's moon Titan in this week's journal
> Nature
> cover story.
>
> Radar imaging data from a July 22, 2006, flyby provide convincing
> evidence for large bodies of liquid on Titan today. A new false-color
> radar view gives a taste of what Cassini saw. Some highlights of the
> article follow below.
>
> Lake Characteristics:
>
> -Radar-dark patches are interpreted as lakes based on their very low
> radar reflectivity and morphological similarities to lakes, including
> associated channels and location in topographic depressions.
>
> -Radar-dark surfaces are smooth and most likely liquid, rock, ice or
> organics. More than 75 radar-dark patches or lakes were seen, ranging
> from 3 kilometers (1.8 miles) to more than 70 kilometers (43 miles)
> across.
>
> -Some lakes appear partly dry, while others seem liquid-filled. Some of
> the partly filled lakes may never have filled fully, or may have partly
> evaporated at some point in the past. The dry lakes have margins or
> rims
> and a radar brightness similar to the rest of the surrounding terrain,
> making them appear devoid of liquid.
>
> -The varying states of how full the lakes are suggest that lakes in
> this
> region of Titan might be temporary on some unknown timescale.
>
> -Approximately 15 of the dark patches seem filled and show no clear
> evidence of erosion. These dark patches resemble terrestrial lakes
> confined within impact basins (for example, Clearwater Lakes in Canada)
> or within volcanic calderas (for example, Crater Lake, Oregon). The
> nest-like nature of these lakes and their limited range of sizes make
> it
> unlikely that they originated from an impact. A volcanic origin for the
> depressions is possible, given their appearance.
>
> -Some lakes have steep margins and very distinct edges, suggesting a
> topographic rim. These lakes are consistent with seepage or groundwater
> drainage lakes.
>
> -Other lakes have diffuse, more scalloped edges, with a gradual
> decrease
> in radar brightness towards the center of the lake. These lakes are
> more
> likely to be associated with channels, and may be either drainage lakes
> or groundwater drainage lakes.
>
> -Yet other lakes have curvy channel-like extensions, similar in
> appearance to terrestrial flooded river valleys (for example Lake
> Powell).
>
> -Bright patches near the lake edges could be small islands peeking
> through the surface. Floating icebergs are unlikely because most
> materials would not float in liquid hydrocarbons.
>
> Other Observations:
>
> -Based on the lake characteristics, Cassini scientists think they are
> observing liquid-filled lakes on Titan today. Another possibility is
> that these depressions and channels formed in the past and have now
> been
> filled by a low-density deposit that is darker than any observed
> elsewhere on Titan. However, the absence of wind-blown features in this
> area makes the low-density hypothesis unlikely.
>
> -These northern hemisphere lakes are the strongest evidence yet that
> Titan's surface and atmosphere have an active hydrological cycle,
> though
> with a condensable liquid other than water. In this cycle, lakes are
> filled through methane rainfall or intersect with a subsurface layer
> saturated with liquid methane.
>
> -As Titan's seasons progress over the 29-year cycle of Saturn's orbit
> around the sun, lakes in the winter hemisphere should expand by steady
> methane rain, while summer hemisphere lakes shrink or dry up entirely.
>
> To read more about the radar imaging data from the July 2006 flyby, go
> to Cassini Finds Lakes on Titan's Arctic Region
> <http://www.jpl.nasa.gov/news/news.cfm?release=2006-097> .
>
> -------------------------------------------------------------
>
> Media contact: Carolina Martinez/JPL
> 818-354-9382
>
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