Mystery of Saturn's 'F ring' cracked, says study

PARIS - An enigmatic ring of icy particles circling Saturn, herded into a narrow ribbon by two tiny moons, was probably born of a cosmic collision, according to a study published Monday.

The so-called F ring, some 140,000 kilometers (87,000 miles) beyond the sixth planet from the Sun, orbits at the border between Saturn's other rings and several moons.

Further toward Saturn, millions of ice blocks populating the planet's haunting halos are prevented from cohering into moons by its powerful tidal forces.

Further out are Saturn's main moons, distant enough to have cohered into spheres with their own gravity: Mimas, Enceladus and Titan, which is the only moon in our Solar System with a substantial atmosphere.

And in the boundary zone F ring's icy particles whirl around the planet in a band barely 100 kilometers (60 miles) across, itself orbited by moons Prometheus and Pandora.     

Scientists have long known that these so-called shepherd moons were partly responsible for keeping the F ring in tight formation.

What they did not know was how this unusual configuration came into being.

Ryuki Hyodo and Keiji Ohtsuki, astronomers from Kobe University in Japan, used computer simulations to show that Prometheus and Pandora are likely the by-product of a collision at the outer edge of Saturn's ring system.

Previous speculation along these lines concluded that two icy mini-moons crashing head-on would have simply disintegrated, adding yet another ring to Saturn's collection.

But what if the objects were made of something less fragile, and hit each other at an angle?

In that case, "such an impact results in only partial disruption" of the mini-moons as opposed to their total destruction, the authors conclude.

The collision would also produce "the formation of a narrow ring of particles" which becomes a new ring.

Hyodo and Ohtsuki further speculate that this sort of process might not be a once-off oddity but rather the "natural outcome" of ring formation under certain conditions for giant gas planets.

This "may explain not only Saturn's F ring, but also features of the Uranian system," Aurelien Crida, a scientist at France's National Centre for Scientific Research wrote in a comment, also in Nature Geoscience.

Saturn is the second largest planet in our Solar System after Jupiter, and has a radius about nine times greater than Earth.

Its spectacular ring system has nine complete rings and several discontinuous arcs, all of them mainly made of ice particles, with lesser amounts of rocky debris and dust.

Some 60 moons circle Saturn, not including hundreds of "moonlets" such as the F ring's Prometheus and Pandora.

Much of the data and high-resolution images we have from Saturn and its rings was collected by the Cassini space probe, which arrived near the giant planet in 2004.

source: interaksyon.com

European space probe lands on comet, but fails to anchor down

BERLIN/FRANKFURT - The European Space Agency landed a probe on a comet on Wednesday, a first in space exploration and the climax of a 10-year-odyssey, but an anchoring system problem may hamper planned investigations into the origins of Earth and the solar system.

The 100-kg (220-pound) lander - virtually weightless on the comet's surface - touched down on schedule at about 11 a.m. ET after a seven-hour descent from its orbiting mothership Rosetta, now located a half-billion kilometers (300 million miles) from Earth.

But during the free-fall to the comet’s surface, harpoons designed to anchor the probe, named Philae, failed to deploy. Flight directors are considering options to ensure the lander does not drift back into space.

“The lander may have lifted off again,” Stefan Ulamec, Philae lander manager at the DLR German Aerospace Center, told reporters. "Maybe today we just didn’t land once, but landed twice. Hopefully we are sitting there on the surface … and can continue our science sequence.”

Scientists hope that samples drilled out from the comet, known as 67P/Churyumov-Gerasimenko, will unlock details about how the planets – and possibly even life – evolved, as the rock and ice that make up comets preserve ancient organic molecules like a time-capsule.

Comets date back to the formation of the solar system some 4.6 billion years ago. Scientists suspect impacting comets delivered water to early Earth.

"How audacious, how exciting, how unbelievable to be able to dare to land on a comet," NASA's director of Planetary Science, Jim Green, said at the European Space Operations Centre in Germany after the successful touchdown.

Manmade craft have now landed on seven bodies in space: the moon, Mars, Venus, Saturn's moon Titan, two asteroids and comet Tempel-1, which was hit by a NASA probe.

Among several records set by the mission, Rosetta has become the first spacecraft to orbit a comet rather than just flying past to take pictures.

Rosetta reached the comet, a roughly 3-by-5 km rock discovered in 1969, in August after a journey of 6.4 billion km that took 10 years, five months and four days - a mission that cost close to 1.4 billion euros or $1.8 billion. ($1 = 0.8022 euro)

"What really nails this experience for me are the images," Daniel Brown, an expert in astronomy at Nottingham Trent University, said via email after three-legged Philae had relayed data and images back to Earth as it moved toward the comet.

"Especially exciting will be getting the results of the samples recovered from below the surface and seeing their chemical composition," he said. (Additional reporting by Irene Klotz in Cape Canaveral, Florida)

source: interaksyon.com

Meteor that hit Russia may have had close shave with sun

PARIS - The meteor that injured over 1,500 people when it exploded and showered debris over Russia in February may have had a close shave with the Sun earlier, researchers said Tuesday.

A study of its composition showed the space rock had undergone "intensive melting" before entering Earth's atmosphere and streaking over the central Russia's Chelyabinsk region in a blinding fireball, they said in a statement.

This "almost certainly" points to a near-miss with the sun, or a collision with another body in the solar system -- possibly a planet or asteroid, said study co-author Victor Sharygin from the Russian Academy of Sciences' Institute of Geology and Mineralogy.

The findings were presented at the Goldschmidt geochemistry conference in Florence, Italy.

The meteor is estimated to have been 17 meters (56 feet) wide before exploding with the equivalent force of 30 times that of the nuclear bomb dropped on Hiroshima during World War II.

Its shockwave blew out windows and damaged buildings across five Russian regions.

The meteor's fragments lie scattered over a large area around Chelyabinsk -- the largest piece is believed to lie at the bottom of Chebarkul Lake from where scientists are trying to raise it.

source: interaksyon.com