Titan's Surface Organics Surpass
Oil Reserves on Earth
Article Courtesy of NASA Feb 13, 2008
An artist's imagination of hydrocarbon pools, icy and rocky terrain on the surface of Saturn's largest moon Titan.
Image credit: Steven Hobbs (Brisbane, Queensland, Australia).
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 data from NASA's Cassini spacecraft. The hydrocarbons rain from the sky, collecting in vast deposits that form lakes and dunes.
The new findings from the study led by Ralph Lorenz, Cassini radar team member from the Johns Hopkins University Applied Physics Laboratory, Laurel, Md., are reported in the Jan. 29 issue of the Geophysical Research Letters.
"Titan is just covered in carbon-bearing material -- it's a giant factory of organic chemicals," said Lorenz. "This vast carbon inventory is an important window into the geology and climate history of Titan."
At a balmy minus 179 degrees Celsius (minus 290 degrees Fahrenheit), Titan is a far cry from Earth. Instead of water, liquid hydrocarbons in the form of methane and ethane are present on the moon's surface, and tholins probably make up its dunes. The term "tholins"was coined by Carl Sagan in 1979 to describe the complex organic molecules at the heart of prebiotic chemistry.
Cassini has mapped about 20 percent of Titan's surface with radar. Several hundred lakes and seas have been observed, with each of several dozen estimated to contain more hydrocarbon liquid than Earth's oil and gas reserves. The dark dunes that run along the equator contain a volume of organics several hundred times larger than Earth's coal reserves.
Proven reserves of natural gas on Earth total 130 billion tons, enough to provide 300 times the amount of energy the entire United States uses annually for residential heating, cooling and lighting. Dozens of Titan's lakes individually have the equivalent of at least this much energy in the form of methane and ethane.
"This global estimate is based mostly on views of the lakes in the northern polar regions. We have assumed the south might be similar, but we really don't yet know how much liquid is there," said Lorenz. Cassini's radar has observed the south polar region only once, and only two small lakes were visible. Future observations of that area are planned during Cassini's proposed extended mission.
Scientists estimated Titan's lake depth by making some general assumptions based on lakes on Earth. They took the average area and depth of lakes on Earth, taking into account the nearby surroundings, like mountains. On Earth, the lake depth is often 10 times less than the height of nearby terrain.
"We also know that some lakes are more than 10 meters or so deep because they appear literally pitch-black to the radar. If they were shallow we'd see the bottom, and we don't," said Lorenz.
The question of how much liquid is on the surface is an important one because methane is a strong greenhouse gas on Titan as well as on Earth, but there is much more of it on Titan. If all the observed liquid on Titan is methane, it would only last a few million years, because as methane escapes into Titan's atmosphere, it breaks down and escapes into space. If the methane were to run out, Titan could become much colder. Scientists believe that methane might be supplied to the atmosphere by venting from the interior in cryovolcanic eruptions. If so, the amount of methane, and the temperature on Titan, may have fluctuated dramatically in Titan's past.
"We are carbon-based life, and understanding how far along the chain of complexity towards life that chemistry can go in an environment like Titan will be important in understanding the origins of life throughout the universe," added Lorenz.
Cassini's next radar flyby of Titan is on Feb. 22, when the radar instrument will observe the Huygens probe landing site.
For images and more information visit: http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov .
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter was designed, developed and assembled at JPL. The radar instrument was built by JPL and the Italian Space Agency, working with team members from the United States and several European countries.
Carolina Martinez 818-354-9382
Jet Propulsion Laboratory, Pasadena, Calif.
This movie, comprised of several detailed images taken by Cassini's radar instrument, shows bodies of liquid near Titan's north pole. These images show that many of the features commonly associated with lakes on Earth, such as islands, bays, inlets and channels, are also present on this cold Saturnian moon. They offer strong evidence that larger bodies seen in infrared images are, in fact, seas. These seas are most likely liquid methane and ethane.
For more than two decades, scientists have debated whether liquids on Titan exist, and if so, where they would be located. Pre-Cassini observations from the 1980s indicated that something on Titan's surface must be re-supplying the methane to its atmosphere. A global ocean was once hypothesized. Subsequently, disconnected lakes or seas were predicted. The discovery of numerous lakes near Titan's north pole by the Cassini radar instrument in July 2006 has confirmed the latter idea, and indicates an apparent preference during the current season for liquids to be located near the north pole.
These new observations of the north polar area show how extensive and widespread these lakes are, and reveal at least one body of liquid that might rightly be called a sea. These seas cover an area about 100,000 square kilometers (about 39,000 square miles), larger than the largest Great Lake, Lake Superior, near the U.S. and Canadian border, whose area is 82,000 square kilometers (about 32,000 square miles). Analysis of the data indicates that the bodies of liquid may be tens of meters in depth.
This high-definition video offers a trip through the north polar area just as Cassini radar saw it. It combines radar swaths seen on several Titan passes: July 22, 2006 (T16); Sept. 23, 2006 (T18); Oct. 9, 2006 (T19); and Feb. 22, 2007 (T25), respectively. The mosaic reveals the extent of the lakes, their shapes and interconnections. The areas believed to be composed of liquids are shown in blue as an aid to interpretation.
The movie begins with an illustration of the relative orbits of Titan and Cassini, both circling Saturn. The spacecraft is seen approaching the planet with a nodding motion as its antenna scans the moon's surface, turning to keep its target in sight. The animation shows all radar swaths, and zooms in for a close look at the many complex shapes the lakes take. Some features that resemble lakes with no liquid may be remnants that have already dried as the northern winter fades into spring. The resolution of the radar data varies from several kilometers to as fine as 300 meters (984 feet). The coverage shown in the video spans from 50 degrees north latitude, almost to the pole, where a small triangular gap in coverage misses the exact pole. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The radar instrument was built by JPL and the Italian Space Agency, working with team members from the United States and several European countries.
For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov .
Image credit: NASA/JPL
Soaring Over Titan: Extraterrestrial Land of Lakes
Published on Dec 12, 2013
This colorized movie from NASA's Cassini mission takes viewers over the largest seas and lakes on Saturn's moon Titan. The movie is made from radar data received during multiple flyovers of Titan from 2004 to 2013. This colorized movie from NASA's Cassini mission shows the most complete view yet of Titan's northern land of lakes and seas. Saturn's moon Titan is the only world in our solar system other than Earth that has stable liquid on its surface. The liquid in Titan's lakes and seas is mostly methane and ethane.
The data were obtained by Cassini's radar instrument from 2004 to 2013. In this projection, the north pole is at the center. The view extends down to 50 degrees north latitude. In this color scheme, liquids appear blue and black depending on the way the radar bounced off the surface. Land areas appear yellow to white. A haze was added to simulate the Titan atmosphere.
Kraken Mare, Titan's largest sea, is the body in black and blue that sprawls from just below and to the right of the north pole down to the bottom right. Ligeia Mare, Titan's second largest sea, is a nearly heart-shaped body to the left and above the north pole. Punga Mare is just below the north pole.
The area above and to the left of the north pole is dotted with smaller lakes. Lakes in this area are about 30 miles (50 kilometers) across or less.
Most of the bodies of liquid on Titan occur in the northern hemisphere. In fact nearly all the lakes and seas on Titan fall into a box covering about 600 by 1,100 miles (900 by 1,800 kilometers). Only 3 percent of the liquid at Titan falls outside of this area.
Scientists are trying to identify the geologic processes that are creating large depressions capable of holding major seas in this limited area. A prime suspect is regional extension of the crust, which on Earth leads to the formation of faults creating alternating basins and roughly parallel mountain ranges. This process has shaped the Basin and Range province of the western United States, and during the period of cooler climate 13,000 years ago much of the present state of Nevada was flooded with Lake Lahontan, which (though smaller) bears a strong resemblance to the region of closely packed seas on Titan.
What Huygens Saw On Titan - New Image Processing
Published on Jan 14, 2015
For the probe landing’s 10th anniversary, a new sequence has been rendered from Huygens’ Descent Imager/Spectral Radiometer (DISR) data. The craft landed on Saturn’s largest moon on 14 Jan 2005. -- Landing Animation: http://goo.gl/6t6XuA - Credit: Erich Karkoschka, DISR team, University of Arizona
Saturn's moon Titan is home to seas and lakes filled with liquid hydrocarbons, but what forms the depressions on the surface? A new study using data from the joint NASA and the European Space Agency (ESA) Cassini mission suggests the moon's surface dissolves in a process that's similar to the creation of sinkholes on Earth.
Apart from Earth, Titan is the only body in the solar system known to possess surface lakes and seas, which have been observed by the Cassini spacecraft. But at Titan's frigid surface temperatures -- roughly minus 292 degrees Fahrenheit (minus 180 degrees Celsius) -- liquid methane and ethane, rather than water, dominate Titan's hydrocarbon equivalent of Earth’s water.
Cassini has identified two forms of methane- and ethane-filled depressions that create distinctive features near Titan's poles. There are vast seas several hundred miles (or kilometers) across and up to several hundred feet (or meters) deep, fed by branching, river-like channels. There also are numerous smaller, shallower lakes, with rounded edges and steep walls that are generally found in flat areas. Cassini also has observed many empty depressions.
The lakes are generally not associated with rivers, and are thought to fill up by rainfall and liquids feeding them from underground. Some of the lakes fill and dry out again during the 30-year seasonal cycle on Saturn and Titan. But exactly how the depressions hosting the lakes came about in the first place is poorly understood.
Recently a team of scientists turned to our home planet for the answer. They discovered that Titan's lakes are reminiscent of what are known as karstic landforms on Earth. These are terrestrial landscapes that result from erosion of dissolvable rocks, such as limestone and gypsum, in groundwater and rainfall percolating through rocks. Over time, this leads to features like sinkholes and caves in humid climates, and salt-pans where the climate is more arid.
The rate of erosion creating such features depends on factors such as the chemistry of the rocks, the rainfall rate and the surface temperature. While all of these aspects clearly differ between Titan and Earth, the researchers think the underlying process may be surprisingly similar.
A team lead by Thomas Cornet of the European Space Agency calculated how long it would take for patches of Titan's surface to dissolve to create these features. They assumed that the surface is covered in solid organic material, and that the main dissolving agent is liquid hydrocarbons, and took into account present-day models of Titan's climate.
The scientists found that it would take around 50 million years to create a 300-foot (100-meter) depression at Titan's relatively rainy polar regions, consistent with the youthful age of the moon's surface.
"We compared the erosion rates of organics in liquid hydrocarbons on Titan with those of carbonate and evaporite minerals in liquid water on Earth," said Cornet. "We found that the dissolution process occurs on Titan some 30 times slower than on Earth due to the longer length of Titan's year and the fact it only rains during Titan summer. Nonetheless, we believe that dissolution is a major cause of landscape evolution on Titan and could be the origin of its lakes."
In addition, scientists calculated how long it would take to form lake depressions at lower latitudes, where the rainfall is reduced. The much longer timescale of 375 million years is consistent with the relative absence of depressions in these geographical locations.
"Of course, there are a few uncertainties: The composition of Titan's surface is not that well constrained, and neither are the long-term precipitation patterns, but our calculations are still consistent with the features we see today on Titan's relatively youthful billion-year-old surface," said Cornet.
"By comparing Titan's surface features with examples on Earth and applying a few simple calculations, we have found similar land-shaping processes that could be operating under very different climate and chemical regimes," said Nicolas Altobelli, ESA's Cassini project scientist. "This is a great comparative study between our home planet and a dynamic world more than a billion kilometers away in the outer solar system."
This research was recently published in the Journal of Geophysical Research, Planets.
NASA Press Release June 19, 2015
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