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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New Photo of Moon's North Pole Reveals Spiral Illusion (SPACE.com)

Here's a view of the moon you'll never see from Earth.

NASA scientists created this mosaic by stitching together 983 images of the moon's North Pole region taken by the Lunar Reconnaissance Orbiter (LRO). The LRO robotic probe, which has been mapping the moon from above since 2009, has acquired thousands of wide-angle camera shots of its polar regions. [Photo of the moon's north pole]

Because the mottled moon only tilts on its access at an angle of 1.54 degrees (as compared to Earth's 23.5 degree tilt) some of its surface never sees sunlight. One goal of the LRO mission is to identify these regions of permanent shadow. The probe took the photos in the composite image above at the height of summer in our satellite's northern hemisphere — the time when the pole is best illuminated. Thus, dark areas, such as those along the inside rims of deep craters and the immediate vicinity of the pole, are probably permanently dark.

The craters around the pole appear to spiral out from it. According to Mark Robinson, principle investigator of the LRO team based at Arizona State University, this is an optical illusion. [The Most Amazing Optical Illusions (and How They Work)]

"Imagine a series of very narrow pie slices collected 12 times each day, one after another," Robinson told Life's Little Mysteries, a sister site to SPACE.com. "It takes roughly 360 slices to fill in the whole pie. Each day the sun direction is progressing around the moon, thus the direction that the sun is striking the surface changes. So the shadow directions slowly progress around the moon, thus leading to the illusion."

This story was provided by Life's Little Mysteries, a sister site to SPACE.com. Follow Natalie Wolchover on Twitter @nattyover. Follow Life's Little Mysteries on Twitter @llmysteries, then join us on Facebook.

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Clues to Moon's Volatile Past Revealed by New Laser Map (SPACE.com)

Nola Taylor Redd, SPACE.com Contributor
Space.com Nola Taylor Redd, Space.com Contributor
space.com – Mon Jun 13, 8:30 am ET

The first comprehensive set of maps of the slopes and craters on the lunar surface is revealing clues about the violent history of the moon.

Unlike on Earth, where wind and water frequently erode geological features, the moon's landscape is less volatile. Features from hundreds of millions, or even billions, of years ago are still visible.

Using the Lunar Orbiter Laser Altimeter (LOLA) on NASA's Lunar Reconnaissance Orbiter, scientists have developed a detailed map of the changes in the contours of the moon from pole to pole. Studying the roughness of these features reveals more about their age and their formation. [See the new moon map here]

Some events are sudden, such as the craters that formed when comets and asteroids crashed into the moon. Mapping the surface provides clues to the ages of the impact sites. The edges of older craters changed as more and more space rocks bombarded them, while newer ones have a sharper, more defined rim.

Other processes occurred gradually. The dark, smoother parts of the moon, known as maria, formed by volcanism.

"As maria age, they change in their roughness properties," researcher Oded Aharonson of California Institute of Technology told SPACE.com. Newer lava flows are smoother than their older counterparts. Aharonson and his colleagues, led by Margaret Rosenburg, also of Caltech, detailed their findings in a paper published in the Journal of Geophysical Research.

Even landslides can reveal activity from the lunar past. Moonquakes and impacts from large objects can cause loose material to slide downhill, or even break off part of a cliff. Examining the steepness of the rubble pile can give clues about the event that shifted it.

In addition to revealing hints about the lunar past, such detailed topography data can help locate potential sites for ice by revealing shaded, stable regions where water is likely to freeze. 

The moon isn't the only place such a detailed examination can come in handy. Other celestial bodies have received similar mapping, though none with quite as much detail as LOLA provides.

Mars, Earth, Venus and Saturn's moon, Titan, have all received some degree of examination, and the Mercury Laser Altimeter is currently scanning the planet closest to the sun. As long as the terrain isn't liquid or gas, it could provide valuable data.

"Understanding the surface roughness properties would be an interesting pursuit for any object with a solid surface in the solar system," Aharonson said.

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Moons Around Asteroid Reveal a Giant Rubble Pile (SPACE.com)

Nola Taylor Redd, SPACE.com Contributor
Space.com Nola Taylor Redd, Space.com Contributor
space.com – 1 hr 20 mins ago

Like the ancient Egyptian queen it was named for, the asteroid Kleopatra has birthed twins — a pair of moons that have helped scientists learn that the huge space rock is a rubble pile rather than a chunk of solid rock.

These two moons, named Alexhelios and Cleoselene after the twin children of the queen, were discovered in 2008. Now, astronomers studying their orbits have deduced that their parent asteroid is a jumble of loosely held rocks.

"That's the point of looking for triple and binary asteroids," study co-author Franck Marchis of the University of California, Berkeley told SPACE.com. "They're the only ones that allow us to measure the mass of the system." [See asteroid Kleopatra and its rocky moons]

Studying the asteroid system

Since the researchers knew Kleopatra's orbit, they were able to use data from various telescopes — including several operated by amateur astronomers — to observe Kleopatra as she passed between Earth and various bright stars.

They also used measurements from as far back as 1980 to examine other, similar passes. For each transit, they timed how long the star "winked" out of view from various positions on the planet. [Photos: Asteroids in Deep Space]

Because each location views the asteroid differently, combining these observations allowed the team to calculate the space rock's size and shape, as well as to view the moons and measure their orbit.

Having determined the orbits of Kleopatra's satellites, the team, lead by primary author Pascal Descamps of the Institut de Mecanique Celeste et de Calculs des Ephemerides (IMCCE) of the Observatoire de Paris, then was able to calculate the mass of the system as a whole.

With mass and size in hand, figuring out the asteroid's density was a breeze. The researchers concluded that the asteroid was not a solid rock.

"Our observations of the orbits of the two satellites of 216 Kleopatra imply that this large metallic asteroid is a rubble pile, which is a surprise," Marchis said in a statement.

The team reported its results in the February issue of the journal Icarus.

Big asteroid surprise

There are a number of smaller asteroids throughout the solar system that are loose, gravitationally bound piles of rock rather than solid objects.

But to find one in such a large system is surprising. At about 135 miles (217 km) in length, Kleopatra is among the largest of these rubble pile asteroids discovered over the past few years, topped only by 174-mile (280 km) 87 Sylvia.

"You expect something (this size) to be less porous," Marchis told SPACE.com.

In fact, given the density of its likely primary iron components, Kleopatra is between 30 and 50 percent empty space.

The rubble pile structure of the asteroid provides clues to its formation, as well as that of its satellites, researchers said. The collision of two larger, rocky asteroids likely resulted in the destruction of one, and the resulting rubble was held together by gravity.

As the pile continued to spin, it slowly shed mass, including its two moons. The outermost moon, Alexhelios, likely spiraled out around 100 million years ago, while the inner moon, Cleoselene, began its journey within the last 10 million years.

Kleopatra was discovered in 1880. Astronomers used stellar transits to determine it was elongated, but it wasn't until 2000 that it was revealed to be shaped more like a dog bone than a cigar. Descamps' team wanted to study whether the bulges at the end were connected to the body of the asteroid or were separate pieces entirely.

The team continues to study other binary or triple asteroid systems, but the tools that allow them to do so are limited.

"The only telescope in the world that can detect these (types of systems) is the Keck, because it has the largest aperture and the best AO (adaptive optic) system," Marchis said.  

However, thousands of astronomers vie for the use of the largest optical and infrared telescope. Marchis expressed his hope that more telescopes like the 33-foot (10-meter) giants in Hawaii will be built, allowing more research to be done.

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