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April 12, 2006, 11:48 PM CT

Lunar Rocks Suggest Meteorite Shower

Lunar Rocks Suggest Meteorite Shower
New age measurements of lunar rocks returned by the Apollo space missions have revealed that a surprising number of the rocks show signs of melting about 3.9 billion years ago, suggesting that the moon - and its nearby neighbor Earth - were bombarded by a series of large meteorites at that time.

The idea that meteorites have hammered the moon's surface isn't news to scientists. The lunar surface is pock-marked with large craters carved out by the impact of crashing asteroids and meteorites, said Robert Duncan, a professor and associate dean in the College of Oceanic and Atmospheric Sciences at Oregon State University.

But the narrow range of the impact dates suggests to scientists that a large spike in meteorite activity took place during a 100-million year interval - possibly the result of collisions in the asteroid belt with comets coming from just beyond our solar system.

Results of the study are being published in Geochimica et Cosmochimica Acta, the journal of the international Meteoritical Society. Co-authors with Duncan are Marc Norman of the Australian National University and John Huard, also an oceanographer at OSU. The study was funded by NASA.

Tiny melted fragments from the lunar rocks were dated at the noble gas geochronology laboratory at Oregon State. Duncan and Huard were able to use radiometric dating techniques to determine when the rocks had melted after being struck by meteorites. What is especially intriguing, Duncan says, is that this apparent spike in meteorite activity took place about 3.8 to 4 billion years ago - an era that roughly coincides with when researchers believe life first began on Earth, as evidenced by the fossil record of primitive one-cell bacteria.........

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April 11, 2006, 11:27 PM CT

Venus Express Enters Orbit Around The Hothouse Planet

Venus Express Enters Orbit Around The Hothouse Planet Artist's impression of the Venus Express orbit insertion on 11 April 2006.
ESA PR 13-2006. This morning, at the end of a 153-day and 400-million km cruise into the inner Solar System beginning with its launch on 9 November 2005, ESA's Venus Express space probe fired its main engine at 09:17 CEST for a 50-minute burn, which brought it into orbit around Venus.

With this firing, the probe reduced its relative velocity toward the planet from 29,000 to about 25,000 km/h and was captured by its gravity field. This orbit insertion manoeuvre was a complete success.

During the next four weeks, the Venus Express probe will perform a series of manoeuvres to reach the scheduled operational orbit for its scientific mission. It will move from its current highly elongated 9-day orbit to a 24-hour polar orbit, culminating at 66,000 kilometres. From this vantage point, the orbiter will conduct an in-depth observation of the structure, chemistry and dynamics of the atmosphere of Venus for at least two Venusian days (486 Earth days).

Enigmatic atmosphere

From prior missions to Venus as well as observations directly from Earth, we already know that our neighbouring planet is shrouded in a thick atmosphere where extremes of temperature and pressure conditions are common. This atmosphere creates a greenhouse effect of tremendous proportions as it spins around the planet in four days in an unexplained 'super-rotation' phenomenon.........

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April 11, 2006, 5:36 PM CT

Saturn Still Wearing Floods

Saturn Still Wearing Floods
The Detroit News reports: Saturn: It craves to be cool again. Cool? Saturn wants to be cool? We're not sure Saturn could handle the cool. We think Saturn needs to focus on what it stands for rather than shooting for cool because we just don't know what Saturn stands for anymore.........

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April 9, 2006, 8:16 PM CT

Cosmic Spider is Good Mother

Hanging above the Large Magellanic Cloud (LMC) - one of our closest galaxies - in what some describe as a frightening sight, the Tarantula nebula is worth looking at in detail. Also designated 30 Doradus or NGC 2070, the nebula owes its name to the arrangement of its brightest patches of nebulosity that somewhat resemble the legs of a spider. This name, of the biggest spiders on Earth, is also very fitting in view of the gigantic proportions of the celestial nebula - it measures nearly 1,000 light years across!.

The Tarantula nebula is the largest emission nebula in the sky and also one of the largest known star-forming regions in all the Milky Way's neighbouring galaxies. Located about 170,000 light-years away, in the southern constellation Dorado (The Swordfish), it can be seen with the unaided eye.

As shown in this image obtained with the FORS1 multi-mode instrument on Eso's Very Large Telescope, its structure is fascinatingly complex, with a large number of bright arcs and apparently dark areas in between. Inside the giant emission nebula lies a cluster of young, massive and hot stars, denoted R 136, whose intense radiation and strong winds make the nebula glow, shaping it into the form of a giant arachnid. The cluster is about 2 to 3 million years old, that is, almost from 'yesterday' in the 13.7 billion year history of the Universe.........

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April 6, 2006, 11:25 PM CT

"A" ring contains more debris

Views of Saturn's stunning ring system from above by the Cassini-Huygens spacecraft now orbiting the planet indicate the prominent A ring contains more debris than once thought, according to a new University of Colorado at Boulder study.

Previous observations with the Voyager spacecraft in the early 1980s found the ring was more transparent, indicating less material, said Joshua Colwell of CU-Boulder's Laboratory for Atmospheric and Space Physics. But new calculations based on May 2005 observations with Cassini's Ultraviolet Imaging Spectrograph, or UVIS, indicates the opacity of the ring is up to 35 percent higher than previously reported.

Because of the uneven distribution of the ring particles - which range in size from dust grains to school buses - the transparency of the rings depends on the angle from which they are viewed, he said. The particles are arranged essentially parallel in long stringy clumps as large as 60 feet across, 16 feet thick and 160 feet long, according to models produced from observation data, said Colwell.

A paper on the subject by Colwell, Larry Esposito and Miodrag Sremcevic of CU-Boulder's LASP appears in the April 1 issue of Geophysical Research Letters, or GRL. Esposito is science team leader for UVIS, a $12.5 million instrument designed and built at CU-Boulder by LASP that is riding on the Cassini spacecraft.........

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April 6, 2006, 10:25 PM CT

Blue Ring Around The Planet Uranus

Blue Ring Around The Planet Uranus
The outermost ring of the planet Uranus turns out to have a bright blue color, as per a report in the April 7 issue of the journal Science. That makes it only the second blue ring to be found in the solar system. The first circles the planet Saturn.

Perhaps not coincidentally, both blue rings are associated with small moons. Astronomers suspect the rings owe their blue color to subtle forces acting on dust in the rings that allow smaller particles to survive while larger ones are recaptured by a moon.

"The outer ring of Saturn is blue and has [the moon] Enceledus right smack at its brightest spot, and Uranus is strikingly similar, with its blue ring right on top of [the moon] Mab's orbit," says Imke de Pater, who is an astronomer at the University of California, Berkeley, and a co-author of the Science paper. "The blue color says that this ring is predominantly submicron-sized material, much smaller than the material in most other rings, which appear red."

De Pater and her co-authors believe the similarity between the outer rings implies an in kind explanation for their blue color. A number of other researchers have ascribed Saturn's blue ring to the small dust, gas and ice particles spewed into Encedadus' orbit by newly discovered plumes on that moon's surface. But that is unlikely to be the case with Mab, a small, dead, rocky ball, about 15 miles across-one-twentieth the diameter of Enceladus.........

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April 4, 2006, 11:55 PM CT

Ocean Dust Busters

Ocean Dust Busters
Like most living things, microscopic marine plants need iron and other minerals to live and grow. On land, soil provides a ubiquitous source of minerals, but how do essential nutrients get into vast watery stretches of the open ocean?

The question has long mystified oceanographers. As per one theory, large swirling currents, called eddies, pump nutrients from the depths up toward the sunlit surface, giving phytoplankton the ingredients they need to flourish. But a larger source of iron may be dust storms, which blow huge quantities of mineral-rich soil particles (called Aeolian dust) out to sea, especially from desert regions in Africa and Asia.

Until now, researchers investigating the latter theory have been stymied by an inability to measure when, where, and how much dust falls into the oceans, said Ed Sholkovitz, a marine geochemist at Woods Hole Oceanographic Institution (WHOI). They have had to rely on dust samples collected on islands.

To remedy this situation, Sholkovitz teamed with three WHOI engineers-Geoff Allsup, David Hosom, and Mike Purcell-who collectively call themselves the Dust Busters. They designed a device, mounted atop a moored buoy, that collects wind-blown particles in the open ocean. Unlike islands, which aren t portable, buoys can be placed in scientifically strategic locales.........

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April 4, 2006, 11:52 PM CT

The 250,000 Ton Punch

The 250,000 Ton Punch
Over the weekend of 9-10 July 2005 a team of UK and US scientists, led by Dr. Dick Willingale of the University of Leicester, used NASAE28099s Swift satellite to observe the collision of NASA's Deep Impact spacecraft with comet Tempel 1.

Reporting today (Tuesday) at the UK 2006 National Astronomy Meeting in Leicester, Dr. Willingale revealed that the Swift observations show that the comet grew brighter and brighter in X-ray light after the impact, with the X-ray outburst lasting a total of 12 days.

"The Swift observations reveal that far more water was liberated and over a longer period than previously claimed," said Dick Willingale.

Swift spends most of its time studying objects in the distant Universe, but its agility allows it to observe a number of objects per orbit. Dr. Willingale used Swift to monitor the X-ray emission from comet Tempel 1 before and after the collision with the Deep Impact probe.

The X-rays provide a direct measurement of how much material was kicked up after the impact. This is because the X-rays were created by the newly liberated water as it was lifted into the comet's thin atmosphere and illuminated by the high-energy solar wind from the Sun.

"The more material liberated, the more X-rays are produced," explained Dr. Paul O'Brien, also from the University of Leicester.........

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March 29, 2006, 10:11 PM CT

dark energy and inflation of the universe

dark energy and inflation of the universe
Looking back 13.7 billion years, astronomers have collected data that tells us, with greater precision than ever before, what happened in the first two-trillionths of a second after the big bang. The data agrees very well with theoretical predictions and may tell us something about the way the universe is behaving today, particularly why it is expanding faster than it ought to be.

"Observation is helping us constrain the theories," said Rachel Bean, Cornell assistant professor of astronomy, who is both a cosmology theorist and a member of the Wilkinson Microwave Anisotropy Probe (WMAP) team, which on March 10 released a high-resolution picture of the cosmic microwave background radiation (CMB), a sort of signature of the big bang.

For cosmologists in general, the WMAP data confirms a widely held theory called the Lambda-CDM (cold dark matter) model, a mathematical description of how the big bang might have played out. For Bean, it throws light on her efforts to explain "dark energy." Recent observations of supernovae suggest that the expansion of the universe is not just "coasting" from the big bang, but that the expansion is accelerating. Some unknown energy source is exerting a force contrary to gravity. Theorists postulate a cosmological constant -- a fundamental property of space -- or something called quintessence -- a sort of energy field.........

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March 25, 2006, 10:59 AM CT

Did "Dark Matter" Create the First Stars?

Did Fig.: Head of the "guitar nebula". The formation contains a fast moving pulsar followed by a tail of gas. Biermann and Kusenko’s postulations about dark matter could explain puzzlingly high pulsar velocities, which lead to such cone-shaped features. Images are from the Planetary Camera aboard the Hubble Space Telescope in 1994 (left) and 2001 (right).

Image: Hubble Space Telescope (NASA/ESA), Shami Shatterjee 200
Researchers discovered that neutrinos have mass through neutrino oscillation experiments. This led to the postulation that "sterile" neutrinos exist - also known as right-handed neutrinos. They do not participate in weak interactions directly, but do interact through their mixing with ordinary neutrinos. The total number of sterile neutrinos in the universe is unclear. If a sterile neutrino only has a mass of a few kiloelectronvolts (1 keV is a millionth of the mass of a hydrogen atom), that would explain the huge, missing mass in the universe, sometimes called "dark matter". Astrophysical observations support the view that dark matter is likely to consist of these sterile neutrinos.

Biermann and Kusenko's theory sheds light on many still unexplained astronomical puzzles. First of all, during the big bang, the mass of neutrinos created in the Big Bang would equal what is needed to account for dark matter. Second, these particles could be the solution to the long-standing problem of why pulsars move so fast.

Pulsars are neutron stars rotating at a very high velocity. They are created in supernova explosions and normally are ejected in one direction. The explosion gives them a "push", like a rocket engine. Pulsars can have velocities of hundreds of kilometres per second - or sometimes even thousands. The origin of these velocities remains unknown, but the emission of sterile neutrinos would explain the pulsar kicks.........

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