An underground ocean on Titan? The apparent detection of low frequency radio waves makes liquid water beneath the surface of the huge Saturnian moon a possibility, according to research led by Fernando Simoes (Centre d’Etudes Terrestres et Planetaires, Saint Maur, France). Simoes and team have been studying what New Scientist is describing as an ‘enigmatic radio signal’ that the European Space Agency’s Huygens probe detected as it descended to Titan’s surface in 2005.
The signal seems not dissimilar to what lightning produces on Earth, where low frequency signals bounce between the ground and the upper atmosphere, in the process attenuating some frequencies while enhancing others. But Titan’s surface seems to be a poor reflector, meaning there may be a better one below. Thus the talk of an ocean, although it’s just one candidate. “We do not need a subsurface ocean but require a subsurface reflector,” Simoes told New Scientist. “If a subsurface ocean exists, the solid-liquid interface would be a good reflector.”
Still in question is the possibility of extraneous vibrations within the radio instrument itself, although the team’s testing has so far failed to reveal any evidence of this. If a body of water is there, it’s probably deep, perhaps fifty kilometers down. A vast ocean rich in ammonia is an exciting prospect indeed, but waiting for future Cassini flybys is necessary for confirmation. If an ocean can be found by analyzing Titan’s behavior under the gravitational pull of Saturn, we’ll have yet more reason for astrobiologists to ponder the outer icy moons as abodes of life.
Hi Paul
Dominic Fortes examined the astrobiological potential of this idea a few years ago – Titan’s ocean looked more hospitable than Europa’s in some respects, though that was before the discovery of oxygen-charged ice on Europa. Solid-phase “electrolysis” (well ion bombardment) means Europa’s ocean has a bit of oxygen supplied to it. Titan’s is highly unlikely to have any free oxygen, but ammonia-water might have surprising effects on biochemistry too. But a whole lot of weird inorganic biochemistry has been suggested too – for example, that big blobs of plastic might exist in the ice crust’s base, rising slowly through the “soft” ice like giant polyethylene diapirs.
Need I say it, but Titan will be a stranger world the more we explore it. Arthur Clarke’s “wax worm” and Stansilaw Lem’s “glass menagerie” might have even stranger analogues in the real world.
Adam, what’s the reference on Lem’s ‘glass menagerie’? I’m not familiar with that one, although I’ve read some Lem.
Hi Paul
In the first part of Lem’s 1986 novel “Fiasco” the protagonist must cross a dangerous part of Titan in a giant teleoperated robot. The region is volcanic and the cryolava is basically plastic glass, solidified into shapes like the skeletons of once living things, like some huge elephant graveyard, or a giant’s glass menagerie. The weird organic chemistry colours it all with streaks of blood red making it even more eerie, and unstable.
“Fiasco” is also a story of a SETI contact going horribly wrong because the humans trying to contact the aliens totally misread what’s occurring on the alien home planet. Has a certain humour through out the story though, making it one of my favourite SETI tales.
Earth’s Future Glimpsed on Titan
http://bcast1.imaginova.com/t?r=2&ctl=14056:4A48D
A desert moon suggests how our planet might end up.
Trickle of Planet Discoveries Becomes a Flood
http://bcast1.imaginova.com/t?r=2&ctl=14053:4A48D
Alien worlds, once hidden from knowledge, are now being discovered in droves.
arXiv:0708.2158
Date: Thu, 16 Aug 2007 08:58:16 GMT (87kb)
Title: Clathrate hydrates as a sink of noble gases in Titan’s atmosphere
Authors: C. Thomas, O. Mousis, V. Ballenegger and S. Picaud
Categories: astro-ph
Comments: Astronomy & Astrophysics Letters, in press
We use a statistical thermodynamic approach to determine
the composition of clathrate hydrates which may form from a
multiple compound gas whose composition is similar to that
of Titan’s atmosphere. Assuming that noble gases are initially
present in this gas phase, we calculate the ratios of xenon,
krypton and argon to species trapped in clathrate hydrates.
We find that these ratios calculated for xenon and krypton
are several orders of magnitude higher than in the coexisting
gas at temperature and pressure conditions close to those of
Titan’s present atmosphere at ground level. Furthermore
we show that, by contrast, argon is poorly trapped in these
ices. This trapping mechanism implies that the gas-phase is
progressively depleted in xenon and krypton when the
coexisting clathrate hydrates form whereas the initial
abundance of argon remains almost constant.
Our results are thus compatible with the deficiency of Titan’s
atmosphere in xenon and krypton measured by the Huygens
probe during its descent on January 14, 2005. However, in
order to interpret the subsolar abundance of primordial Ar
also revealed by Huygens, other processes that occurred
either during the formation of Titan or during its evolution
must be also invoked.
http://arxiv.org/abs/0708.2158 , 87kb
Sequestration of ethane in the cryovolcanic subsurface of Titan
Authors: Olivier Mousis, Bernard Schmitt
(Submitted on 7 Feb 2008)
Abstract: Saturn’s largest satellite, Titan, has a thick atmosphere dominated by nitrogen and methane. The dense orange-brown smog hiding the satellite’s surface is produced by photochemical reactions of methane, nitrogen and their dissociation products with solar ultraviolet, which lead primarily to the formation of ethane and heavier hydrocarbons. In the years prior to the exploration of Titan’s surface by the Cassini-Huygens spacecraft, the production and condensation of ethane was expected to have formed a satellite-wide ocean one kilometer in depth, assuming that it was generated over the Solar system’s lifetime. However, Cassini-Huygens observations failed to find any evidence of such an ocean.
Here we describe the main cause of the ethane deficiency on Titan: cryovolcanic lavas regularly cover its surface, leading to the percolation of the liquid hydrocarbons through this porous material and its accumulation in subsurface layers built up during successive methane outgassing events. The liquid stored in the pores may, combined with the ice layers, form a stable ethane-rich clathrate reservoir, potentially isolated from the surface. Even with a low open porosity of 10% for the subsurface layers, a cryovolcanic icy crust less than 2300 m thick is required to bury all the liquid hydrocarbons generated over the Solar system’s lifetime.
Comments: accepted for publication in Astrophysical Journal
Subjects: Astrophysics (astro-ph)
Cite as: arXiv:0802.1033v1 [astro-ph]
Submission history
From: Olivier Mousis [view email]
[v1] Thu, 7 Feb 2008 18:16:11 GMT (153kb)
http://arxiv.org/abs/0802.1033
Saturn’s orange moon Titan has hundreds of times more
liquid hydrocarbons than all the known oil and natural gas
reserves on Earth, according to new Cassini data. The
hydrocarbons rain from the sky, collecting in vast deposits
that form lakes and dunes.
More at:
http://www.esa.int/esaSC/SEMCSUUHJCF_index_0.html
CASSINI SPACECRAFT FINDS OCEAN MAY EXIST BENEATH TITAN’S CRUST
PASADENA, Calif. – NASA’s Cassini spacecraft has discovered evidence
that points to the existence of an underground ocean of water and
ammonia on Saturn’s moon Titan. The findings made using radar
measurements of Titan’s rotation will appear in the March 21 issue of
the journal Science.
“With its organic dunes, lakes, channels and mountains, Titan has one
of the most varied, active and Earth-like surfaces in the solar
system,” said Ralph Lorenz, lead author of the paper and Cassini
radar scientist at the Johns Hopkins Applied Physics Laboratory in
Laurel, Md., “Now we see changes in the way Titan rotates, giving us
a window into Titan’s interior beneath the surface.”
Members of the mission’s science team used Cassini’s Synthetic
Aperture Radar to collect imaging data during 19 separate passes over
Titan between October 2005 and May 2007. The radar can see through
Titan’s dense, methane-rich atmospheric haze, detailing
never-before-seen surface features and establishing their locations
on the moon’s surface.
Using data from the radar’s early observations, the scientists and
radar engineers established the locations of 50 unique landmarks on
Titan’s surface. They then searched for these same lakes, canyons and
mountains in the reams of data returned by Cassini in its later
flybys of Titan. They found prominent surface features had shifted
from their expected positions by up to 19 miles. A systematic
displacement of surface features would be difficult to explain unless
the moon’s icy crust was decoupled from its core by an internal
ocean, making it easier for the crust to move.
“We believe that about 62 miles beneath the ice and organic-rich
surface is an internal ocean of liquid water mixed with ammonia,”
said Bryan Stiles of NASA’s Jet Propulsion Laboratory (JPL) in,
Pasadena, Calif. Stiles also is a contributing author to the paper.
The study of Titan is a major goal of the Cassini-Huygens mission
because it may preserve, in deep-freeze, many of the chemical
compounds that preceded life on Earth. Titan is the only moon in the
solar system that possesses a dense atmosphere. The moon’s atmosphere
is 1.5 times denser than Earth’s. Titan is the largest of Saturn’s
moons, bigger than the planet Mercury.
“The combination of an organic-rich environment and liquid water is
very appealing to astrobiologists,” Lorenz said. “Further study of
Titan’s rotation will let us understand the watery interior better,
and because the spin of the crust and the winds in the atmosphere are
linked, we might see seasonal variation in the spin in the next few
years.”
Cassini scientists will not have long to wait before another go at
Titan. On March 25, just prior to its closest approach at an altitude
of 620 miles, Cassini will employ its Ion and Neutral Mass
Spectrometer to examine Titan’s upper atmosphere. Immediately after
closest approach, the spacecraft’s Visual and Infrared Mapping
Spectrometer will capture high-resolution images of Titan’s southeast
quadrant.
The Cassini-Huygens mission is a cooperative project of NASA, the
European Space Agency and the Italian Space Agency. The mission is
managed by JPL, a division of the California Institute of Technology
in Pasadena. The Cassini orbiter also was designed, developed and
assembled at JPL.
For information about Cassini visit: http://www.nasa.gov/cassini/