The Cassini Solstice mission has discovered what appears to be a miniature version* of the Nile River on Saturn's largest moon, Titan.
The 400 kilometer (250 mile) long feature -- from 'headwaters' to a
large sea -- is the longest extraterrestrial river ever to be discovered
and imaged to such high resolution.
Using Cassini's radar imaging instruments, mission scientists were
able to deduce that the feature is indeed a river as the dark, smooth
surface within the meanders and channel suggest the presence of a
liquid.
ANALYSIS: The 'Tropical' Lakes of Saturn's Moon Titan
Titan is known to have vast lakes -- the only other body in the solar
system, apart from Earth, to possess a cycle of liquids on its surface.
However, the thick Titan atmosphere is a frigid one, meaning liquid
water couldn't possibly flow. The liquids on Titan are therefore
composed of hydrocarbons such as methane and ethane.
Interestingly, using this observation of a vast river system on Titan
reveals not only that rivers flow, it could also trace the path of
fault lines on the Saturnian moon, suggestive of fractures in Titan's
bedrock.
"Though there are some short, local meanders, the relative
straightness of the river valley suggests it follows the trace of at
least one fault, similar to other large rivers running into the southern
margin of this same Titan sea," said Jani Radebaugh, Cassini radar team
associate at Brigham Young University.
"Such faults -- fractures in Titan's bedrock -- may not imply plate
tectonics, like on Earth, but still lead to the opening of basins and
perhaps to the formation of the giant seas themselves."
ANALYSIS: Need a Vacation? Visit Titan's Exotic Ontario Lacus
The discovery of vast river systems on Titan was perhaps inevitable.
Cassini has previously confirmed the presence of large masses of liquids
including Ontario Lacus,
a lake in the southern hemisphere composed of liquid ethane. Rainfall
has also been detected in the atmosphere, hinting not of a hydrological
cycle (which gives us water rain, rivers and oceans on Earth), but of a
methane cycle.
It is hard not to imagine what such a river system would look like
when standing next to it. But looking at this radar observation, many
familiar river features such as meanders and channels can be seen.
Titan is a complex and fascinating little world laced with complex
prebiotic chemistry. Apart from the Huygens probe that landed on the
surface in 2005, there have been no other surface missions and plans for
future missions look iffy at best.
ANALYSIS: Titan's Hazy History and the Potential for Life
Titan might be shrouded in a cold, high pressure atmosphere that
makes it difficult for our robots to explore, but it's hard to ignore
the fact that the ingredients for the basic chemistry for life is there
in abundance -- could there be a form of life there, perhaps taking
advantage of liquid methane and ethane rather than water? We may be
waiting some time to find out.
*In comparison, the Nile is 6,650 kilometers (4,132 miles) long.
Image credit: NASA/JPL-Caltech/ASI
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