Radar study puts spotlight on Saturn moon Titan's hydrocarbon seas
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[July 17, 2024]
By Will Dunham
WASHINGTON (Reuters) - NASA's Cassini spacecraft, which explored Saturn
and its icy moons, including the majestic Titan, ended its mission with
a death plunge into the giant ringed planet in 2017. But some of the
voluminous data gathered by Cassini during its 13 years of surveying the
Saturnian system is only now being fully examined.
Cassini's radar observations are providing intriguing new details about
the seas of liquid hydrocarbons on the surface of Titan, our solar
system's second-largest moon and a place of interest in the search for
life beyond Earth.
Titan, shrouded in a smog-like orange haze, is the only known world
other than Earth exhibiting liquid seas on the surface, though they are
not composed of water but rather nitrogen and the organic compounds
methane and ethane, components of natural gas.
The study involved three seas near Titan's north pole: Kraken Mare, the
largest, covering an area comparable to Eurasia's Caspian Sea; Ligeia
Mare, the second-largest and comparable in area to North America's Lake
Superior; and Punga Mare, roughly equivalent to Africa's Lake Victoria.
The chemical composition of these seas - methane-rich versus ethane-rich
- was found to vary depending on their latitude. The study also
documented the extent and distribution of sea surface ripples,
indicating active tidal currents and increased roughness near estuaries
- the mouths of rivers.
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Titan, 3,200 miles (5,150 km) wide, is our solar system's second-biggest
moon behind Jupiter's Ganymede and is larger than the planet Mercury.
Titan and Earth are the only worlds in the solar system where liquids
rain down from clouds, flow as rivers into seas and lakes on the surface
and evaporate back up to the sky to begin the hydrological process
again.
On Earth, water rains down from clouds. On Titan, clouds spew methane -
which is a gas on Earth - in liquid form due to the frigid climate.
"Titan is really an Earth-like world with a diverse set of very familiar
surface morphologies shaped by a methane-based hydrologic system
operating in a dense nitrogen atmosphere," said Cornell University
engineer and a planetary scientist Valerio Poggiali, lead author of the
study published on Tuesday in the journal Nature Communications.
"Seas and lakes of liquid hydrocarbons dot the surface in the polar
regions, especially the northern one. Precipitation-fed channels flow
into these seas creating estuaries, in some cases deltas," Poggiali
added.
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![](../images/071724PIX/news_f10.jpg)
Titan, Saturn's largest moon, appears in front of the ringed planet
in this view from NASA's Cassini spacecraft in this handout released
by NASA August 29, 2012. REUTERS/ NASA/JPL-Caltech/SSI/File Photo
![](http://archives.lincolndailynews.com/2024/Jul/17/images/ads/current/24ENCORE4097_070124.jpg)
The Cassini data indicated the rivers carry pure liquid methane that
then mixes into the more ethane-rich liquids of the seas, much as
freshwater in Earth's rivers mixes into saltwater oceans.
"Titan's seas are pulled by Saturn's massive gravity, just like our
seas, and the tidal range on some of its shorelines may be around a
foot (30 cm). Because the tidal period - Titan's day - is long, 16
Earth days, the tidal cycle is slow, so the tidal currents are
generally weak," said planetary scientist and study co-author Ralph
Lorenz of the Johns Hopkins University Applied Physics Laboratory.
The study used "bistatic" radar data collected during Cassini flybys
of Titan, three in 2014 and one in 2016. Cassini aimed a radio beam
at targets on Titan's surface, which then reflected toward a
receiving antenna on Earth. This provided richer information about
the composition of the reflecting surface and its roughness than
ordinary Cassini "monostatic" radar, which bounces a radio signal
off a target and back to the point of origin.
"This is likely the last untouched dataset that the Cassini
spacecraft left us," Poggiali said.
Titan boasts environments with conditions considered potentially
suitable for life. For instance, Titan appears to harbor a vast
subsurface ocean of liquid water.
"Are the heavy organic molecules produced in Titan's atmosphere
prebiotic in nature?" Poggiali asked, referring to chemistry that
could led to formation of life. "Has all this organic material ever
been in contact with liquid water? We believe that similar
interactions could have led to the origin of life on our planet,
with the generation of molecules able to produce energy or store
information."
(Reporting by Will Dunham, Editing by Rosalba O'Brien)
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