Category: Titan

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NASA’s Cassini mission has detected liquid hydrocarbons on Saturn’s moon Titan, in a large, glassy lake near the moon’s south pole. Before the Cassini mission began, scientists thought Titan would have global oceans of methane, ethane and other light hydrocarbons. But after more than 40 close flybys of Titan by Cassini, data showed no global oceans exist. However hundreds of dark, lake-like features are present. Until now, it was not known whether these features were liquid or simply dark, solid material. Using Cassini’s Visual and Infrared Mapping Spectrometer (VIMS), which identifies the chemical composition of objects by the way matter reflects light, a liquid ethane lake 235 kilometers (150 miles) long was detected. This makes Titan the only body in our solar system beyond Earth known to have liquid on its surface.

“This is the first observation that really pins down that Titan has a surface lake filled with liquid,” said Bob Brown of the University of Arizona, Tucson, leader of the VIMS instrument.

Scientists had deduced through earlier observations that there was likely liquid on Titan, but this is the first incontrovertible evidence. (Emily Lakdawalla at the Planetary Society explains this excellently.)

“Detection of liquid ethane confirms a long-held idea that lakes and seas filled with methane and ethane exist on Titan,” said Larry Soderblom, a Cassini interdisciplinary scientist with the U.S. Geological Survey. “The fact we could detect the ethane spectral signatures of the lake even when it was so dimly illuminated, and at a slanted viewing path through Titan’s atmosphere, raises expectations for exciting future lake discoveries by our instrument.”

Titan’s hazy, nitrogen and methane atmosphere makes it difficult to study the moon’s surface. The liquid ethane was identified using a technique that removed the interference from the atmospheric hydrocarbons.

The VIMS instrument observed a lake, called Ontario Lacus, in Titan’s south polar region during a close Cassini flyby in December 2007. The lake is roughly 20,000 square miles (7,800 square miles) in area, slightly larger than North America’s Lake Ontario.

The ethane is in a liquid solution with methane, other hydrocarbons and nitrogen. At Titan’s surface temperatures, approximately 300 degrees Fahrenheit below zero, these substances can exist as both liquid and gas. Titan shows overwhelming evidence of evaporation, rain, and fluid-carved channels draining into what, in this case, is a liquid hydrocarbon lake.

Earth has a hydrological cycle based on water and Titan has a cycle based on methane. Scientists ruled out the presence of water ice, ammonia, ammonia hydrate and carbon dioxide in Ontario Lacus. The observations also suggest the lake is evaporating. It is ringed by a dark beach, where the black lake merges with the bright shoreline. Cassini also observed a shelf and beach being exposed as the lake evaporates.

“During the next few years, the vast array of lakes and seas on Titan’s north pole mapped with Cassini’s radar instrument will emerge from polar darkness into sunlight, giving the infrared instrument rich opportunities to watch for seasonal changes of Titan’s lakes,” Soderblom said.

More information is available at NASA’s Cassini site, JPL’s Cassini site, and the Univeristy of Arizona’s VIMS site.

Even before the Cassini spacecraft entered the Saturn system, scientists were predicting that Saturn’s moon Titan would be quite Earth-like. And every image that’s been returned of Titan’s clouds, lakes, rivers, and other landforms is proving them right. In 2005 Cassini’s imaging radar discovered a massive area of sand dunes around Titan’s equatorial region. Although these dark, windblown dunes look much like sand dunes on Earth (they’ve been compared to mountainous drifts of coffee grounds), scientists are finding that the dunes are likely made of organic molecules that are not anything at all like sand.

Titan is known to have massive amounts of hydrocarbons. New observations of Titan’s sand dunes raise the possibility that much of the sand grows from hydrocarbon particulates fallen from Titan’s thick atmosphere. Once on the ground, the particulates join together and become sand grain-size particles.

This process is called sintering – where the particles are heated enough to melt together. Scientist Jason W. Barnes of NASA’s Ames Research Center says that this sintering may produce particles that are about the same size as sand grains – between 0.18-0.25 millimeters, which are perfect for blowing in the wind and drifting into dunes.

So, this process is quite the opposite of what happens to sand on Earth, which comes from silicates, gypsum, or rock that have broken down to finer grains. But on Titan, the small hydrocarbon particulates grow together into larger grains. Barnes says the process is extremely slow, but Titan has been around long enough for this to have occurred.

Based on measurements from Cassini, the dunes are 100-200 meters high and are between 1 and 79 kilometers long. Not all over Titan’s surface has been imaged, but scientists believe up to 20 % of Titan’s surface could be covered by these hydrocarbon dunes.

Original News Source: JPL

If you’re planning a visit to Saturn’s moon Titan, make sure you bring an umbrella. You’ll need it. Not to protect you from water raining down; on frigid Titan, where temperatures dip below 180-degrees Celsius, all the water is completely frozen. No, according to scientists, there’s a steady drizzle of liquid methane coming down in the mornings.

New infrared images gathered by Hawaii’s W.M. Keck Observatory and Chile’s Very Large Telescope show that Titan’s Xanadu region experiences a steady drizzle of methane during its lengthy morning. The concept of morning is a little misleading, since Titan takes about 16 Earth days to complete one rotation. So, the “morning” drizzle actually lasts around 3 Earth days, dissipating around 10:30 a.m. local time.

Astronomers aren’t actually sure if this is a moon-wide phenomenon, or just localized around the Xanadu region of Titan. Even though large lakes and seas have been discovered around the moon’s poles, no process had been discovered that fills them with liquid… until now.

Reporting their findings in the latest issue of the online journal Science Express, researchers from UC Berkeley note that, “widespread and persistent drizzle may be the dominant mechanism for returning methane to the surface from the atmosphere and closing the methane cycle.”

The new Keck/VLT images show a widespread cloud cover of frozen methane at a height of 25 to 35 kilometres. And then there are liquid methane clouds below 20 kilometres, and finally rain falling at the lowest elevations.

The droplets of liquid methane in the rain clouds are 1,000 times larger than water vapour here on Earth, and this surprisingly makes them harder to detect. Since the droplets are larger, but still carry the same amount of moisture, they’re much more spread out, making the clouds extremely diffuse, and nearly invisible.

How much liquid is trapped in the clouds? If you squeezed them all out and spread the liquid across the surface of Titan, it would coat the entire moon to a depth of about 1.5 cm. And that’s actually the same amount as we’d get if you did the same thing with the Earth’s clouds.

Original Source: UC Berkeley News Release

Take a look at the image attached to this story. If you didn’t know any better, you’d think you were looking at a rugged coastline somewhere on Earth. Maybe some island in the Mediterranean, or Norwegian fjord. Nope, you’re looking at a completely alien world: Titan.

NASA’s Cassini spacecraft took this image on May 12, 2007 during its most recent flyby of Saturn’s largest moon. During the flyby, its radar instrument captured this image using its radar instrument. Smooth surfaces, like liquid are seen as black, while the textured regions are land.

While other bodies of liquid such as lakes have been seen on Titan before, nothing has had these kinds of features: channels, islands, bays, and other terrain you’d see on Earth. But instead of water, this liquid is probably a mixture of ethane and methane. Since there are no brighter regions in the liquid regions of the image, scientists are assuming the ocean exceeds tens of metres deep.

The image is about 160 kilometers (100 miles) by 270 kilometers (170 miles) across.

Original Source: NASA/JPL/SSI/ESA News Release

Since the twin Voyager spacecraft flew past Saturn’s moon Titan, Scientists have been excited about what its hazy atmosphere can tell us about the earliest days of our own planet. The Voyagers discovered that Titan’s atmosphere is swirling with hydrocarbons and other complex organic molecules that could be the building blocks of life. The latest findings from NASA’s Cassini spacecraft have uncovered these organic molecules floating higher in Titan’s atmosphere than scientists originally thought possible.

This latest research has been published in the May 11, 2007 edition of the Journal Science. It shows that these organic aerosols, called tholins, have been found in altitudes higher than 1,000 kilometres (620 miles) above the surface of Titan. And these molecules are formed differently than how scientists originally believed.

This inquiry is important because the Titan’s environment is thought to be very similar to the Earth’s early history, before the first life formed. A similar process could have happened here.

Original Source: SwRI News Release