Saturn Moon's Icy Secrets Shine Bright in New NASA Images (SPACE.com)

New details about Enceladus, one of the icy moons orbiting Saturn, are revealed in new images of the bright and shimmering cosmic body.

The snapshots highlight some of the grooves in Enceladus' south polar region, including unexpected textures in the moon's ice. The photos, taken by NASA's Cassini spacecraft on Nov. 6, are the highest-resolution images of this region obtained so far, according to NASA officials.

The new images of Enceladus come from data collected by a special radar instrument on Cassini, called the synthetic aperture radar.

The area photographed by Cassini does not include Enceladus' famous "tiger stripes," which are huge fissures on the moon's ice-covered surface that eject plumes of ice particles and water vapor. These icy geysers cover regions just a few hundred miles away from the stripes, NASA scientists said.

Researchers are scrutinizing an area on Enceladus that appears to have a very rough surface texture that glimmers peculiarly bright in Cassini's radar images. This patch is located at around 63 degrees south latitude and 51 degrees west longitude. [Video: Clearest Enceladus Views Yet Nabbed by Cassini Radar]

"It's puzzling why this is some of the brightest stuff Cassini has seen," Steve Wall, deputy leader of Cassini's radar team at NASA's Jet Propulsion Laboratory in Pasadena, Calif., said in a statement. "One possibility is that the area is studded with rounded ice rocks. But we can't yet explain how that would happen."

Scientists are also investigating an area where Cassini spotted grooved, water-ice bedrock. The spacecraft's images reveal unusual undulations and intricate patterns that have not previously been seen. This area is located at around 65 degrees south latitude and 293 degrees west longitude on the icy moon.

Cassini's observations also reveal a central groove in this area that is about 2,100 feet (650 meters) deep and 1.2 miles (2 kilometers) wide, with sides that slope at an angle of about 33 degrees.

Enceladus is the sixth-largest moon around Saturn, and new images of the satellite show some similarities to Titan, the largest moon orbiting the ringed planet.

The western foothills in the so-called Xanadu region of Titan are also very bright, as are regions surrounding a large impact crater called Sinlap. Whether these luminous areas shine because of the same or very different processes will be the subject of research as scientists continue to learn more about the moons of Saturn, NASA officials said.

NASA's Cassini spacecraft was launched in 1997 and arrived at Saturn in 2004. The spacecraft carried the European Space Agency's Huygens lander, which landed on Titan soon after Cassini arrived in orbit around the ringed planet.

In 2008, Cassini completed its primary mission to explore Saturn, its rings and moons. Since then, the mission has been extended twice, most recently to 2017.

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Moon & Jupiter to Shine Close Together Tonight (SPACE.com)

Joe Rao, SPACE.com Contributor
Space.com Joe Rao, Space.com Contributor
space.com – Thu Oct 13, 6:30 pm ET

The two most brilliant objects in our current night sky will make for an eye-catching duo tonight (Oct. 13), weather permitting. 

Looking low to the east-northeast around 7:30 p.m. local daylight time, you’ll see a nearly full waning gibbous moon. Sitting just to the right of the moon will be the lordly light belonging to the largest planet in our solar system: Jupiter.  

Jupiter will hover about 5 degrees from the moon's right. Your clenched fist held at arm's length covers about 10 degrees, so moon and Jupiter will be separated by about half a fist. 

The sky map of the moon and Jupiter here shows how they will appear together tonight.

Cosmic dance of Jupiter and moon

If you stay up through the night, you may notice the moon slowly pulling away from Jupiter at a rate of one lunar diameter per hour, and the orientation between the two bright objects will change as well. [Photos of Jupiter: Solar System's Largest Planet]

By around 1 a.m. local daylight time (early Friday morning), the moon will seem to hover high above and to Jupiter's left. By 6:30 a.m. — with morning twilight rapidly brightening the sky in the east — the moon will seem to hang high and almost directly above Jupiter.

In the days that follow, the moon will pull away to the east and diminish in illumination, leaving glorious Jupiter to rule the October night.

On Oct. 28, Jupiter will arrive at opposition against the sparse background stars of the constellation Aries, the Ram. Since it is then opposite to the sun, the planet rises at sunset, crosses the sky from east to west during the night and sets at sunrise. 

Beginning in November, Jupiter will already be up in the eastern sky when the sun goes down. This will continue for the rest of the fall season in the Northern Hemisphere.

Jupiter shining bright

Opposition generally brings a "superior" planet (an outer planet as compared with Earth) closest to the Earth, and this is why Jupiter now shines more brilliantly than it has all year.

Astronomers use a reverse number scale to measure the brightness of objects in the sky, with smaller numbers corresponding to brighter objects. A negative number, for example, represents an extremely bright object. At an eye-popping magnitude of - 2.9 — fully four times brighter than Sirius, the brightest star — Jupiter is far brighterthan any nighttime star.

But this year's apparition of Jupiter is an exceptionally good one. Although "Big Jupe" comes to opposition every 13 months (every time the Earth sweeps between it and the sun), 2011 is also Jupiter's year of perihelion. This is when it is closest to the sun in its 12-year orbit, so it's also particularly close to the Earth. 

Jupiter is 33 light-minutes away this month, compared to its most distant opposition of the last decade in 2005. 

Actually, last October's opposition placed Jupiter about 1.5 million miles (2.4 million kilometers) closer than this year, but that makes no difference in how bright Jupiter is now compared to a year ago, and in a telescope, its apparent disk size measures only 0.4 percent smaller. Truth be told, for the next month or so, Jupiter's disk is the most generous that a planet can be: large and fully illuminated, and — when observed with a good telescope — decorated with numerous bands and other intricate features. 

In fact, there are now more features and surface area visible on this one disk than on all the other planets combined. And after this year, Jupiter will not attain such a pinnacle of extreme brilliance again until the year 2022.

Jupiter's moons visible in telescopes

On Thursday evening, good binoculars or a telescopewill reveal three of the famous Galilean satellites during the early evening hours: Ganymede and Europa on one side of Jupiter, with Callisto on the other.  Io and its shadow will be passing in front of Jupiter, an event that can be seen in moderate-sized telescopes. 

Io's shadow will be evident as a tiny black dot and is called a shadow transit. Io itself may be invisible from insufficient contrast with the background disk of Jupiter, but it can be readily seen for a short while as a white dot just as it is about to move off of Jupiter's west limb (at 10:03 p.m. EDT, 0230 GMT).

Io's shadow will move off Jupiter's disk 23 minutes earlier at 9:40 p.m. EDT (0140 GMT).  

If you snap an amazing photo of Jupiter, the moon or the moon and Jupiter together, and would like to share the image with SPACE.com for a possible gallery or story please contact managing editor Tariq Malik at Harvest Moon of 2011: Amazing Skywatcher Photos Video: Top 10 Amateur Telescopes10 Coolest New Moon Discoveries

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Climate scientists shine new light on methane mystery

Farmers work in a padi field at Khokana village, located south of Nepal's capital Kathmandu July 27, 2011.

Credit: Reuters/Navesh Chitrakar

By David Fogarty

SINGAPORE | Thu Aug 11, 2011 7:25am EDT

SINGAPORE (Reuters) - Atmospheric levels of methane, 20 times more powerful than carbon dioxide (CO2) at trapping heat, stayed steady for two decades to 2006 on wider fertilizer use to grow rice or a surge in natural gas demand, according to two separate studies in the journal Nature.

Climate researcher Fuu Ming Kai from the Massachusetts Institute of Technology's Singapore research center said in one study that methane output from rice fields in the Northern Hemisphere dropped during the period as fertilizers replaced manure and because of reduced water use.

In the second study, Murat Aydin at the University of California, Irvine, concluded that a drop in methane emissions from more efficient burning of fossil fuels and a surge in natural gas demand.

The studies aim to solve a puzzle that has confounded climate scientists for years: why did methane levels in the atmosphere, after rising steadily for many years, taper off in the mid-1980s in a dip lasting two decades?

Solving the puzzle is crucial because methane levels have risen more than 150 percent since the start of the industrial revolution, compared with CO2's 40 percent increase, and are on the rise again.

While the studies reach different conclusions, both studies point to human activities as the reason for the slowdown.

"In general most of the methane sources come from the Northern Hemisphere," Fuu told Reuters.

The main methane sources come from burning fossil fuels, rice paddies, coal mines, livestock and clearing and burning of tropical forests.

"We looked at the isotope data to see how it's changed over the past 20 to 30 years. And what we saw is a trend in the isotope signature and especially in the Northern Hemisphere."

Fuu said long-term data and comparing methane levels between the both hemispheres helped researchers conclude that about half the decrease in Northern Hemisphere methane emissions could be explained by reduced emissions from rice agriculture in Asia over the past three decades.

"It is important to know what the mechanism is behind the slow down. If you know this, you can adopt a suitable policy to reduce methane emissions," Fuu said.

Aydin concluded the drop coincided with rapid natural gas production as the fuel became increasingly price competitive with oil and other fossil fuel, instead of flaring it off. The gains came even though overall fossil fuel use increased as cleaner burning technologies helped keep methane emissions in check, he said.

"We speculate that the rising economic value of natural gas during the late 20th Century and the deployment of cleaner technologies led to sharp reductions in the release of light hydrocarbons into the atmosphere," the study says.

(Editing by Ed Lane)

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