Cassini Finds Likely Subsurface Ocean on Saturn Moon

PASADENA, Calif. -- Data from NASA's Cassini spacecraft have revealed Saturn's moon Titan likely harbors a layer of liquid water under its ice shell.

Researchers saw a large amount of squeezing and stretching as the moon orbited Saturn. They deduced that if Titan were composed entirely of stiff rock, the gravitational attraction of Saturn would cause bulges, or solid "tides," on the moon only 3 feet (1 meter) in height. Spacecraft data show Saturn creates solid tides approximately 30 feet (10 meters) in height, which suggests Titan is not made entirely of solid rocky material. The finding appears in today's edition of the journal Science.

"Cassini's detection of large tides on Titan leads to the almost inescapable conclusion that there is a hidden ocean at depth," said Luciano Iess, the paper's lead author and a Cassini team member at the Sapienza University of Rome, Italy. "The search for water is an important goal in solar system exploration, and now we've spotted another place where it is abundant."

Titan takes only 16 days to orbit Saturn, and scientists were able to study the moon's shape at different parts of its orbit. Because Titan is not spherical, but slightly elongated like a football, its long axis grew when it was closer to Saturn. Eight days later, when Titan was farther from Saturn, it became less elongated and more nearly round. Cassini measured the gravitational effect of that squeeze and pull.

Scientists were not sure Cassini would be able to detect the bulges caused by Saturn's pull on Titan. By studying six close flybys of Titan from Feb. 27, 2006, to Feb. 18, 2011, researchers were able to determine the moon's internal structure by measuring variations in the gravitational pull of Titan using data returned to NASA's Deep Space Network (DSN).

"We were making ultrasensitive measurements, and thankfully Cassini and the DSN were able to maintain a very stable link," said Sami Asmar, a Cassini team member at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "The tides on Titan pulled up by Saturn aren't huge compared to the pull the biggest planet, Jupiter, has on some of its moons. But, short of being able to drill on Titan's surface, the gravity measurements provide the best data we have of Titan's internal structure."

An ocean layer does not have to be huge or deep to create these tides. A liquid layer between the external, deformable shell and a solid mantle would enable Titan to bulge and compress as it orbits Saturn. Because Titan's surface is mostly made of water ice, which is abundant in moons of the outer solar system, scientists infer Titan's ocean is likely mostly liquid water.

On Earth, tides result from the gravitational attraction of the moon and sun pulling on our surface oceans. In the open oceans, those can be as high as two feet (60 centimeters). While water is easier to move, the gravitational pulling by the sun and moon also causes Earth's crust to bulge in solid tides of about 20 inches (50 centimeters).

The presence of a subsurface layer of liquid water at Titan is not itself an indicator for life. Scientists think life is more likely to arise when liquid water is in contact with rock, and these measurements cannot tell whether the ocean bottom is made up of rock or ice. The results have a bigger implication for the mystery of methane replenishment on Titan.

"The presence of a liquid water layer in Titan is important because we want to understand how methane is stored in Titan's interior and how it may outgas to the surface," said Jonathan Lunine, a Cassini team member at Cornell University, Ithaca, N.Y. "This is important because everything that is unique about Titan derives from the presence of abundant methane, yet the methane in the atmosphere is unstable and will be destroyed on geologically short timescales."

A liquid water ocean, "salted" with ammonia, could produce buoyant ammonia-water liquids that bubble up through the crust and liberate methane from the ice. Such an ocean could serve also as a deep reservoir for storing methane.

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 for NASA's Science Mission Directorate in Washington. DSN, also managed by JPL, is an international network of antennas that supports interplanetary spacecraft missions and radio and radar astronomy observations for the exploration of the solar system and the universe. The network also supports selected Earth-orbiting missions. Cassini's radio science team is based at Wellesley College in Massachusetts. JPL is a division of the California Institute of Technology in Pasadena. 

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Forest Recovering from Mt. St. Helens Explosion

Mt. St. Helens exploded 32 years ago on May 18. It began with a small series of earthquakes and culminated with the volcano erupting, a cataclysmic collapse of the flank of the mountain and the largest landslide in recorded history.

This time series of data shows the explosion and subsequent recovery of life on the volcano. Landsat, a satellite program operated by NASA and the U.S. Geological Survey acquired the images between 1979 and 2011. In them, scientists have an unprecedented opportunity to witness how life recovers from devastation.

The animation begins with vegetation as red because early Landsat satellites couldn't 'see' blue light. That changed with launch of Landsat 5 in 1984 and its natural color abilities.

The collapse of the mountain was like uncorking a bottle of champagne. Fifty-seven people died when rocks, hot ash, gas and steam exploded out of the Earth. The blast debris, which is gray in the images, covered over 230 square miles (600 square kilometers) and blew down 4 billion board-feet of timber.

The landslide buried 14 miles (23 kilometers) of the North Fork Toutle River with an average of 150 feet (46 meters) of rocks, dirt and uprooted trees. In some places the debris was as deep as 600 feet (180 meters) high.

The squarish beige patches visible in the upper right and lower left of the animation show logging on the mountain both before and after the eruption.

This image was created using the reflected light from the near infrared, green and red portions of the spectrum from instruments aboard Landsat satellites 2 and 3 and from the blue, green and red portions of the spectrum from instruments aboard Landsat satellites 5 and 7.

Landsat 2 launched in 1975 and provided scientific data for 7 years until 1982. Landsat 3 launched in 1978 and ran for 5 years until1983. NASA launched Landsat 5 in 1984 and it ran for a record-breaking 28 years. Landsat 7 is still up and running; it was launched in 1999. The data from these and other Landsat satellites has been instrumental in our understanding of forest health, storm damage, agricultural trends, urban growth and many other ongoing changes to our land. 

Study Finds Surprising Arctic Methane Emission Source

The fragile and rapidly changing Arctic region is home to large reservoirs of methane, a potent greenhouse gas. As Earth’s climate warms, the methane, frozen in reservoirs stored in Arctic tundra soils or marine sediments, is vulnerable to being released into the atmosphere, where it can add to global warming. Now a multi-institutional study by Eric Kort of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., has uncovered a surprising and potentially important new source of Arctic methane: the ocean itself.

Kort, a JPL postdoctoral scholar affiliated with the Keck Institute of Space Studies at the California Institute of Technology in Pasadena, led the analysis while he was a student at Harvard University, Cambridge, Mass. The study was conducted as part of the HIAPER Pole-to-Pole Observations (HIPPO) airborne campaign, which flew a specially instrumented National Science Foundation (NSF)/National Center for Atmospheric Research (NCAR) Gulfstream V aircraft over the Pacific Ocean from nearly pole to pole, collecting atmospheric measurements from Earth’s surface to an altitude of 8.7 miles (14 kilometers). The campaign, primarily funded by NSF with additional funding from NCAR, NASA and the National Oceanic and Atmospheric Administration, was designed to improve our understanding of where greenhouse gases are originating and being stored in the Earth system.

During five HIPPO flights over the Arctic from 2009 to 2010, Kort’s team observed increased methane levels while flying at low altitudes over the remote Arctic Ocean, north of the Chukchi and Beaufort Seas. The methane level was about one-half percent larger than normal background levels.

But where was the methane coming from? The team detected no carbon monoxide in the atmosphere that would point to possible contributions from human combustion activities. In addition, based on the time of year, location and nature of the emissions, it was extremely unlikely the methane was coming from high-latitude wetlands or geologic reservoirs.

By comparing locations of the enhanced methane levels with airborne measurements of carbon monoxide, water vapor and ozone, they pinpointed a source: the ocean surface, through cracks in Arctic sea ice and areas of partial sea ice cover. The cracks expose open Arctic seawater, allowing the ocean to interact with the air, and methane in the surface waters to escape into the atmosphere. The team detected no enhanced methane levels when flying over areas of solid ice.

Kort said previous studies by others had measured high concentrations of methane in Arctic surface waters, but before now no one had predicted that these enhanced levels of ocean methane would find their way to the overlying atmosphere.

So how is the methane being produced? The scientists aren’t yet sure, but Kort hinted biological production from living things in Arctic surface waters may be a likely culprit. “It’s possible that as large areas of sea ice melt and expose more ocean water, methane production may increase, leading to larger methane emissions,” he said. He said future studies will be needed to understand the enhanced methane levels and associated emission processes and to measure their total contribution to overall Arctic methane levels.

“While the methane levels we detected weren’t particularly large, the potential source region, the Arctic Ocean, is vast, so our finding could represent a noticeable new global source of methane,” he added. “As Arctic sea ice cover continues to decline in a warming climate, this source of methane may well increase. It’s important that we recognize the potential contribution from this source of methane to avoid falsely interpreting any changes observed in Arctic methane levels in the future.”

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5 NASA rockets to light up stretch of East Coast skies

A quintuple rocket launch promises to put on a spectacular, but brief, overnight light show of luminescent vapor trails in the skies above the U.S. East Coast tonight, weather permitting. The sky display may puzzle and amaze some unsuspecting observers, so before you make that phone call to your local news or police, here is why this is happening and when you may see it.

The bright phenomenon will be caused by NASA's Anomalous Transport Rocket Experiment (ATREX), which will launch five chemical-bearing suborbital rockets in about five minutes to test the flow of winds and electrical currents at high altitudes. The rockets will blast off from NASA's Wallops Flight Facility on Wallops Island, Va., on the Atlantic coast during a window that opens tonight at midnight EDT and closes at 1:30 a.m. EDT Thursday.

As part of the mission, the five rockets will each release a chemical tracer that should inscribe brilliant milky white trails in the nighttime sky and allow scientists and the general public to actually "see" high-altitude winds at the edge of space, according to a NASA description.

Midnight launch lights
If all goes well, NASA intends to photograph the trails from three different sites: Wallops Island, southern New Jersey and the outer banks of North Carolina. Should weather conditions be unfavorable, the firings will be delayed to another night, with alternate launch dates available between March 16 and April 3.

Three different types of sounding rockets will be used to create the five cloud trails: two Terrier Improved Malemutes, two Terrier Improved Orions and one Terrier Oriole. These small rockets are powerful enough to launch instruments off the planet on short flights, but not strong enough to reach orbit and circle the Earth.

Each rocket will eject a stream of the chemical trimethyl aluminum (TMA), which will be illuminated at high altitudes by the sun (which will be below the local horizon at ground level). Initially, the clouds are expected to glow in reddish hues, then quickly turn to white, They could persist in the sky for as long as 20 minutes before fading completely away.

The ATREX project is aimed at gathering information to better understand the processes responsible for the high-altitude jet stream winds located 60 to 65 miles (97 to 105 kilometers) above the surface of the Earth.

That works out to a potential viewing radius of up to 450 miles (725 km), suggesting that the resultant cloud trails might be glimpsed from perhaps as far north as southern Vermont and New Hampshire, as far south as the border of coastal North and South Carolina and as far west as central West Virginia.


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Cassini Testing Part of Its Radio System

PASADENA, Calif. -- Engineers with NASA's Cassini mission are conducting diagnostic testing on a part of the spacecraft's radio system after its signal was not detected on Earth during a tracking pass in late December. The spacecraft has been communicating with Earth using a backup part.

The issue occurred with the ultra-stable oscillator, which is used for one type of radio science experiment and also as a means of sending data back to Earth. The spacecraft is currently using an auxiliary oscillator, whose frequency stability is adequate for transmitting data from the spacecraft to Earth. Tests later this month will help mission managers decide whether it will be possible to bring the ultra-stable oscillator back into service.

Some of the data collected for the radio science experiment using the auxiliary oscillator will be of lesser quality than that from the ultra-stable oscillator. Signals used for occultation experiments – where scientists analyze how radio signals are affected as they travel through Saturn's rings or the atmospheres of Saturn and its moons back to Earth – will be of lesser quality. A second kind of radio science investigation using gravity measurements to probe the internal structure of Saturn or its moons will not be affected. Cassini carries 12 science experiments.

The cause is still under investigation, but age may be a factor. The spacecraft launched in 1997 and has orbited Saturn since 2004. Cassini completed its prime mission in 2008 and has had two additional mission extensions. This is the first time its ultra-stable oscillator has had an issue.

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Will NASA’s Kepler find another Earth? Possibly in 2012 say scientists

It’s the question the entire scientific community is asking: Will NASA’s Kepler find another Earth, and how soon?

2011 was full of reports that astronomers are one step closer to discovering another habitable Earth-like planet outside of our own solar system. NASA earlier this year confirmed the discovery of the first-ever planet in a habitable zone outside our solar system. That planet is roughly twice the size of Earth. French astronomers earlier this year confirmed the first exoplanet to meet key requirements for sustaining life, and just last week NASA announced the discovery of the first two Earth-sized planets orbiting a sun-like star.

In September, Kepler scientists turned science fiction into reality when they announced the first observation of a planet with two suns — such as Luke Skywalker’s home planet Tatooine in the “Star Wars” film series. Such planets are called “circumbinary” planets because they orbit a “binary pair” of stars. Until a few months ago, people only suspected two-star planets might exist.

The latest batch of discovery has left NASA clamoring for more. Speaking earlier this year, Geoffrey Marcy of the University of California, Berkeley, said he expects NASA’s Kepler Telescope to discover a habitable planet within the coming year.

“Sooner or later, Kepler will find a lukewarm planet with a size making it probably Earthlike,” said Geoffrey Marcy of the University of California, Berkeley. “We’re no more than a year away” from such a discovery, he said.

“We are finally there,” said David Charbonneau, an astronomer at the Harvard-Smithsonian Center for Astrophysics, who is part of the team leading the Kepler mission, led by colleague Francois Fressin. “This demonstrates for the first time that Earth-size planets exist around other stars and that we can detect them,” Fressin said.

NASA officials announced earlier this year that the Kepler telescope, which has reportedly already discovered more than 2,000 new planet candidates, is nearly doubling its previously known count. Still, scientists said the space agency should focus on identifying which planets are most likely to maintain the environment necessary for water to exist, and, possibly, life.

Meanwhile, a number of scientists said the latest news is exciting in that Kepler’s batch of discoveries show a number of Earth-like planets exist outside of the Solar System. Astronomers says the number of discoveries in 2011 prove that Kepler can indeed find planets as small as our own, an encouraging sign that planet hunters would someday succeed in the goal of finding Earth-like abodes in the heavens. Since the first Jupiter-size exoplanets, as they are known, were discovered nearly 15 years ago, astronomers have been chipping away at the sky, finding smaller and smaller planets.

“The primary goal of the Kepler mission is to find Earth-sized planets in the habitable zone,” said Francois Fressin of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, lead author of a new study published in the journal Nature. “This discovery demonstrates for the first time that Earth-size planets exist around other stars, and that we are able to detect them.”

The Kepler science team uses ground-based telescopes and the Spitzer Space Telescope to review observations on planet candidates the spacecraft finds. The star field that Kepler observes in the constellations Cygnus and Lyra can only be seen from ground-based observatories in spring through early fall. The data from these other observations help determine which candidates can be validated as planets.

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Surprisingly Earth-like features revealed on Saturn's moon

After meticulously stitching together images that were gathered over six years by a NASA spacecraft in orbit around Saturn, astronomers have created a global map of the surface of Titan, the ringed planet's largest moon, and it features some surprisingly Earth-like geological features.

An international team of astronomers, led by the University of Nantes in France, created the striking mosaic of Titan's surface using infrared images taken by the Visual and Infrared Mapping Spectrometer (VIMS) aboard NASA's Cassini spacecraft.

The global map and animations were presented Oct. 4 at the European Planetary Science Congress and the American Astronomical Society's Division of Planetary Science in Nantes, France.

The researchers used images that were taken during the Cassini mission's first 70 flybys of Titan. But, piecing together the map was an intricate and painstaking project because scientists had to comb through the pictures on a pixel-by-pixel basis to adjust illumination differences and other distortions caused by Titan's thick and hazy atmosphere, said Stéphane Le Mouélic, of the University of Nantes.

"As Cassini is orbiting Saturn and not Titan, we can observe Titan only once a month on average," Le Mouélic said in a statement. "The surface of Titan is therefore revealed year after year, as pieces of the puzzle are progressively put together. Deriving a final map with no seams is challenging due to the effects of the atmosphere — clouds, mist etc. — and due to the changing geometries of observation between each flyby."

Lifting the veil on Saturn's largest moon
Titan is the only moon known to be cloaked in a dense atmosphere, which is composed mainly of nitrogen. It also has clouds of methane and ethane, and ongoing research has presented increasing evidence for methane rain on the large, frigid moon.

Since Titan is veiled in an opaque atmosphere, its surface is difficult to study with visible light cameras, and only a few specific infrared wavelengths can penetrate the haze. Cassini's infrared instruments and radar signals provide an intriguing glimpse down to the surface of the frozen body, which, as the new global map reveals, has some interesting Earth-like features.


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Antarctic underground lake could hold secrets of Earth's past

A lake hidden beneath three kilometres of ice in the western Antarctic could reveal what life on Earth looked like up to a million years ago and narrow down the search for extraterrestrial life.

A team of British scientists will arrive in Antarctica next week in the hope of becoming the first people to reach one of the frozen continent's 387 underground lakes.

Lake Ellsworth is likely to contain bacteria, microbes and other simple life forms which experts believe will have been sealed away from the rest of the Earth for up to a million years.

Samples of water and sediment to be collected from the lake could reveal undiscovered life forms which existed on Earth before the lake froze over, and what the planet's past climate was like.

The sediment collected from the bed of the lake is expected to support the theory that the West Antarctic Ice Sheet, which is currently on the wane thanks to higher global temperatures, has melted and collapsed in the past.

Scientists also hope to learn how any life is able to exist in one of the most extreme environments on the planet – a clue which could help astronomers searching for life beyond Earth.

A similar operation being carried out at Vostok, a different underground Antarctic lake, by Russian scientists has been beset by delays and technical problems for several years, but the British team hope to drill through the ice, obtain their samples and bring them to the surface in a matter of hours.

The expedition marks the climax of a 15-year project by eight British universities, the British Antarctic Survey and the National Oceanography Centre, funded principally by a £7 million grant from the National Environment Research Council.


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Complete Coverage of NASA's Falling Satellite UARS

A dead NASA satellite, called the Upper Atmosphere Research Satellite (UARS), is falling uncontrolled toward Earth and is expected to crash to the ground today (Sept. 23) or Saturday. Agency officials are unable to pinpoint the exact time and location of the fall, but have said there is little risk of debris landing in populated areas. SPACE.com is providing full coverage of the UARS re-entry, including a look at the issues surrounding orbital debris and space situational awareness.

Editor's note: If you snap a photo or observe the re-entry of NASA's UARS satellite and want to share it with SPACE.com for a story or gallery, contact managing editor Tariq Malik at: tmalik@space.com.

"NASA’s decommissioned Upper Atmosphere Research Satellite fell back to Earth between 11:23 p.m. EDT Friday, Sept. 23 and 1:09 a.m. EDT Sept. 24. The Joint Space Operations Center at Vandenberg Air Force Base in California said the satellite penetrated the atmosphere over the Pacific Ocean. The precise re-entry time and location are not yet known with certainty."

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