Hundreds of Methane Plumes Erupting Along East Coast

In an unexpected discovery, hundreds of gas plumes bubbling up from the seafloor were spotted during a sweeping survey of the U.S. Atlantic Coast.
Even though ocean explorers have yet to test the gas, the bubbles are almost certainly methane, researchers report today (Aug. 24) in the journal Nature Geoscience.
"We don't know of any explanation that fits as well as methane," said lead study author Adam Skarke, a geologist at Mississippi State University in Mississippi State.

Surprising seeps

Between North Carolina's Cape Hatteras and Massachusetts' Georges Bank, 570 methane seeps cluster in about eight regions, according to sonar and video gathered by the National Oceanographic and Atmospheric Administration ship Okeanos Explorer between 2011 and 2013. The vast majority of the seeps dot the continental slope break, where the seafloor topography swoops down toward the Atlantic Ocean basin. [Gallery: Amazing images of Atlantic Methane Seeps]
The Okeanos Explorer used sound waves to detect the methane bubbles and map the seafloor. The technique, called multibeam sonar, calculates the time and distance it takes for sound waves to travel from the ship to the seafloor and back. The sonar can also detect the density contrast between gas bubbles and seawater.
Huge canyons etched in the shallow continental shelf also hide bubble plumes, as well as diverse ecosystems that are based on methane-loving bacteria. In 2013, researchers explored a handful of these seeps with Jason, a remotely operated vehicle, finding them teeming with crabs, fish and mussel beds. In Norfolk canyon off the coast of Virginia, researchers from the University of North Carolina at Wilmington discovered the largest methane seep ever found in the Atlantic Ocean, and possibly all the world's oceans. [Photos: Unique Life Found at East Coast Gas Seep]
Most of the methane seeps are in water less than 1,640 feet (500 meters) deep. Most of these shallow methane seeps seem to arise from microbes blurping out methane, the researchers said. The researchers did find some deeper methane vents, at which the ROV Jason glimpsed patches of methane hydrate. This is the icy mix of methane and water that appears when deep ocean pressures and cold temperatures force methane to solidify. Any type of methane gas can form hydrates.

An illustration of the Atlantic margin showing the relationship between methane seeps and seafloor features.
Credit: A. Skarke and C. Ruppel/Nature Geoscience

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While methane vents are common around the world, only three natural gas seeps — where methane escapes from seafloor sediments — had been found off the East Coast before 2012.
"It was a surprise to find these features," Skarke said. "It was unexpected because many of the common things associated with methane gas do not exist on the Atlantic margin."
Gas, gas, gas?
The East Coast is a passive margin, and methane isn't expected to come out of this environment. The margin hasn't been squeezed or pulled by plate tectonic activity for tens of millions of years, and that means a lack of escape routes for methane. "I usually describe passive margins as cold, old and boring," said study co-author Carolyn Ruppel, chief of the U.S. Geological Survey gas hydrates project in Woods Hole, Massachusetts. [In Images: How North America Grew as a Continent]
Also missing from the Atlantic Coast are layers of salt, which are responsible for the Gulf of Mexico's oil and gas.

Without more exploring, the researchers can't say for sure why there are so many methane plumes along the Atlantic coastline. "It's a huge research area that needs to be pursued," Ruppel said.
If the East Coast could hide hundreds of bubbling methane pits, then it's likely there are nearly 30,000 more awaiting discovery in the world's oceans, the researchers said.
"These processes may be happening in places we didn't expect them," Skarke said.

Cup corals and bubblegum corals live on rock near the edge of the mussel bed.
Credit: NOAA Okeanos Explorer Program, 2013 Northeast U.S. Canyons Expedition

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There's also a good chance more methane vents will be found off the East Coast, but that doesn't mean one should expect new drilling platforms popping up offshore to extract the gas, the researchers said. "We have no evidence to suggest this material would be a recoverable resource," Skarke told Live Science. "There is no evidence whatsoever that there are conventional deep-seated oil and gas reservoirs underneath the Atlantic margin."
The more likely scenario: A fleet of research ships hurries to claim the seeps. The methane seeps are near ports where many of the U.S. research ships dock. The ease of access has set off an exploration stampede, with several new projects in planning stages or already funded.
"We're setting the stage for a decade of discovery," Ruppel said.
From the Arctic to Atlantic
Interest is running high because the seeps could be a laboratory for studying how methane hydrates respond to climate change.
Methane is a greenhouse gas that disappears more quickly than carbon dioxide in the atmosphere, but has more warming power than carbon dioxide. Millions of tons of methane are frozen in Arctic permafrost, both on land and in the seafloor. Recently, several studies have warned that rapid warming in the Arctic could upset these deposits, melting them and freeing the gas. This would boost the planet's greenhouse gas levels and could accelerate climate change.

A close-up of methane hydrate observed at a depth of 3,460 feet (1,055 meters) off the U.S. Atlantic Coast.
Credit: NOAA Okeanos Explorer Program/2013 Northeast U.S. Canyons Expedition

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"Now we have a study site where we can monitor these locations and see how they change," said David Valentine, a geochemist at the University of California, Santa Barbara, who was not involved in the study. "Finally we have a place where we can begin to address some of the questions about how water temperatures are influencing methane."
At present, scientists think the East Coast seeps don't contribute much methane to climate change.
Most of the methane gas dissolves in the ocean before reaching the surface, Ruppel said. The total amount of gas is also much smaller than sources on land, such as cows or gas drilling. "It's probably on the order of a feedlot of methane," Valentine said. However, some shallow-water seeps could vent methane to the surface, and researchers expect that future surveys will uncover even more shallow seeps. These regions only received a cursory look during the survey.
Even though the methane may not escape to the atmosphere, the gas still adds to the ocean's overall carbon budget — which is still a wildly uncertain number.
"It's not a huge number, but it's an important number for us to know," Ruppel said.

'Magic Island' Possibly Seen in Seas of Saturn's Huge Moon Titan

http://www.space.com/26326-peculiar-island-appears-on-saturn-moon-before-and-after-spacecraft-shots-video.html

Scientists may have spotted waves in the seas of Saturn's moon Titan, as depicted in this image.

A mysteriously bright anomaly winked in and out of existence on the seas of Saturn's largest moon, Titan — potentially the first time waves, bubbles or some other unknown features have been seen there, scientists say.

Scientists usually call this spot a "transient feature," but the researchers have playfully dubbed it "Magic Island." Titan, the largest of Saturn's 62 known moons, is 50 percent wider than Earth's moon and 80 percent more massive. You can watch a video about the "Magic Island" on Space.com.

"What I think is really special about Titan is that it has liquid methane and ethane lakes and seas, making it the only other world in the solar system that has stable liquids on its surfaces," lead study author Jason Hofgartner, a planetary scientist at Cornell University,told Space.com. "It not only has lakes and seas, but also rivers and even rain. It has what we call a hydrological cycle, and we can study it as an analog to Earth's hydrological cycle — and it's the only other place we know of where we can do that." [Titan, Saturn's Largest Moon.

Using radar aboard NASA's Cassini spacecraft, Hofgartner and his colleagues peered through Titan's thick, hazy atmosphere to analyze Ligeia Mare, the second-largest sea on Titan. Ligeia Mare is named after one of the Sirens from Greek mythology, and is about 48,650 square miles (126,000 square kilometers) in size, making it larger than North America's Lake Superior.

After the Cassini probe sent data to researchers in July 2013, the researchers flipped between older Titan photos and the newly processed images, to look for any hints of change. This is a long-standing method used to discover asteroids, comets and other worlds.

"With flipping, the human eye is pretty good at detecting change," Hofgartner said in a statement.

Prior to the July 2013 data, the region the scientists analyzed was completely devoid of features, including waves

Titan's seas and lakes are usually pretty dark, Hofgartner said. "The way the radar system works is by transmitting radio beams at Titan, which scatter off its surface and back at the radar system. The seas are normally so flat; all the radar energy is scattered away and doesn't come back to the spacecraft, so the seas appear perfectly dark," he explained.
 
However, in July 2013, Cassini detected features that are essentially as bright as the surrounding terrain. The anomaly disappeared after subsequent observations.

"These are not stagnant seas — they are not unchanging and constant in state," Hofgartner said. "They are active and do change."

It remains uncertain "precisely what caused this 'magic island' to appear, but we'd like to study it further," Hofgartner said in a statement. He and his colleagues detailed their findings June 22 in the journal Nature Geoscience.

The bright anomaly occupies an area of about 6.2 by 12.4 miles (10 by 20 km), Hofgartner said.

"We don't think this is one large feature, but it is probably broken up into a few features — some no bigger than about 1 km by 1 km [0.6 by 0.6 miles]," Hofgartner said. "However, we do think at least one of them is bigger than 1 km by 1 km."

The researchers do not think this anomaly is an alien creature or spacecraft. Rather, now that Titan's northern hemisphere is entering its summer season, "it's probably receiving enough solar energy to drive winds and power other phenomena," Hofgartner said.

The seas are normally very smooth on Titan, "with features no taller than 1 to 3 millimeters (.04 to 0.12 inches), making them smoother than any natural surface on Earth," Hofgartner said. "This is because the winds on Titan have likely not been strong enough to create waves. Now, however, the winds might be getting stronger, and we might be seeing waves," he added.

Another possibility is that the bright anomaly could represent gases pushing up from the seafloor and rising as bubbles. It could also represent solids becoming buoyant with the onset of warmer temperatures and floating on the surface, or solids that are neither sunken nor floating, but rather suspended in the sea like silt in a delta on Earth. "As summer comes on Titan, we hope to learn more about the seas there," Hofgartner said.

Discovering more about how the seas of Titan work "can help us with future plans to explore Titan," Hofgartner said. "One plan is to put a boat or raft on Titan's seas to study it in more detail, and understanding what processes are happening there now can tell us what instrumentation to bring and also how to improve the safety of the craft as well," he said

NASA's Cassini Spacecraft Reveals Clues About Saturn Moon

NASA's Cassini spacecraft is providing scientists with key clues about Saturn's moon Titan, and in particular, its hydrocarbon lakes and seas.
Titan is one of the most Earth-like places in the solar system, and the only place other than our planet that has stable liquid on its surface.
Cassini's recent close flybys are bringing into sharper focus a region in Titan's northern hemisphere that sparkles with almost all of the moon's seas and lakes. Scientists working with the spacecraft's radar instrument have put together the most detailed multi-image mosaic of that region to date. The image includes all the seas and most of the major lakes. Some of the flybys tracked over areas that previously were seen at a different angle, so researchers have been able to create a flyover of the area around Titan's largest and second largest seas, known as Kraken Mare and Ligeia Mare, respectively, and some of the nearby lakes.
"Learning about surface features like lakes and seas helps us to understand how Titan's liquids, solids and gases interact to make it so Earth-like," said Steve Wall, acting radar team lead at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "While these two worlds aren't exactly the same, it shows us more and more Earth-like processes as we get new views."
These new images show Kraken Mare is more extensive and complex than previously thought. They also show nearly all of the lakes on Titan fall into an area covering about 600 miles by 1,100 miles (900 kilometers by 1,800 kilometers). Only 3 percent of the liquid at Titan falls outside of this area.

"Scientists have been wondering why Titan's lakes are where they are. These images show us that the bedrock and geology must be creating a particularly inviting environment for lakes in this box," said Randolph Kirk, a Cassini radar team member at the U.S. Geological Survey in Flagstaff, Ariz. "We think it may be something like the formation of the prehistoric lake called Lake Lahontan near Lake Tahoe in Nevada and California, where deformation of the crust created fissures that could be filled up with liquid."

A creative application of a method previously used to analyze data at Mars also revealed that Ligeia Mare is about 560 feet (170 meters) deep. This is the first time scientists have been able to plumb the bottom of a lake or sea on Titan. This was possible partly because the liquid turned out to be very pure, allowing the radar signal to pass through it easily. The liquid surface may be as smooth as the paint on our cars, and it is very clear to radar eyes.

The new results indicate the liquid is mostly methane, somewhat similar to a liquid form of natural gas on Earth.

"Ligeia Mare turned out to be just the right depth for radar to detect a signal back from the sea floor, which is a signal we didn't think we'd be able to get," said Marco Mastrogiuseppe, a Cassini radar team associate at Sapienza University of Rome. "The measurement we made shows Ligeia to be deeper in at least one place than the average depth of Lake Michigan."

One implication is that Cassini scientists now can estimate the total volume of the liquids on Titan. Based on Mastrogiuseppe's work, calculations made by Alexander Hayes, of Cornell University in Ithaca, N.Y., show there are about 2,000 cubic miles (9,000 cubic kilometers) of liquid hydrocarbon, about 40 times more than in all the proven oil reservoirs on Earth.

As Cassini gets closer to northern summer in the Saturn system, mission scientists look forward to potentially the most exciting time for weather at Titan's northern hemisphere

NASA's Cassini spacecraft has spied long-standing methane lakes, or puddles, in the "tropics" of Saturn's moon Titan. One of the tropical lakes appears to be about half the size of Utah's Great Salt Lake, with a depth of at least 3 feet (1 meter). 

The result, which is a new analysis of Cassini data, is unexpected because models had assumed the long-standing bodies of liquid would only exist at the poles. The findings appear in this week's issue of the journal Nature.

Where could the liquid for these lakes come from?  "A likely supplier is an underground aquifer," said Caitlin Griffith, the paper's lead author and a Cassini team associate at the University of Arizona, Tucson. "In essence, Titan may have oases."

Understanding how lakes or wetlands form on Titan helps scientists learn about the moon's weather. Like Earth's hydrological cycle, Titan has a "methane" cycle, with methane rather than water circulating. In Titan's atmosphere, ultraviolet light breaks apart methane, initiating a chain of complicated organic chemical reactions. But existing models haven't been able to account for the abundant supply of methane.

"An aquifer could explain one of the puzzling questions about the existence of methane, which is continually depleted," Griffith said. "Methane is a progenitor of Titan's organic chemistry, which likely produces interesting molecules like amino acids, the building blocks of life."

Global circulation models of Titan have theorized that liquid methane in the moon's equatorial region evaporates and is carried by wind to the north and south poles, where cooler temperatures cause methane to condense. When it falls to the surface, it forms the polar lakes. On Earth, water is similarly transported by the circulation, yet the oceans also transport water, thereby countering the atmospheric effects. 

The latest results come from Cassini's visual and infrared mapping spectrometer, which detected the dark areas in the tropical region known as Shangri-La, near the spot where the European Space Agency's Huygens probe landed in 2005. When Huygens landed, the heat of the probe's lamp vaporized some methane from the ground, indicating it had landed in a damp area. 

Areas appear dark to the visual and infrared mapping spectrometer when liquid ethane or methane are present. Some regions could be shallow, ankle-deep puddles. Cassini's radar mapper has seen lakes in the polar region, but hasn't detected any lakes at low latitudes. 

The tropical lakes detected by the visual and infrared mapping spectrometer have remained since 2004. Only once has rain been detected falling and evaporating in the equatorial regions, and only during the recent expected rainy season. Scientists therefore deduce the lakes could not be substantively replenished by rain. 

"We had thought that Titan simply had extensive dunes at the equator and lakes at the poles, but now we know that Titan is more complex than we previously thought," said Linda Spilker, the Cassini project scientist based at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "Cassini still has multiple opportunities to fly by this moon going forward, so we can't wait to see how the details of this story fill out."