The research aims to produce valid information and must use reliable instruments that guarantee accurate and make it quantifiable and possible reproducibility. Allowing the exclusion or at least control prejudice of personal insights and trends that may distort the results.
sábado, 31 de julio de 2010
Dead Sea Scrolls Mystery Solved?
The recent decoding of a cryptic cup, the excavation of ancient Jerusalem tunnels, and other archaeological detective work may help solve one of the great biblical mysteries: Who wrote the Dead Sea Scrolls?
The new clues hint that the scrolls, which include some of the oldest known biblical documents, may have been the textual treasures of several groups, hidden away during wartime—and may even be "the great treasure from the Jerusalem Temple," which held the Ark of the Covenant, according to the Bible.
The Dead Sea Scrolls were discovered more than 60 years ago in seaside caves near an ancient settlement called Qumran. The conventional wisdom is that a breakaway Jewish sect called the Essenes—thought to have occupied Qumran during the first centuries B.C. and A.D.—wrote all the parchment and papyrus scrolls.
But new research suggests many of the Dead Sea Scrolls originated elsewhere and were written by multiple Jewish groups, some fleeing the circa-A.D. 70 Roman siege that destroyed the legendary Temple in Jerusalem.
"Jews wrote the Scrolls, but it may not have been just one specific group. It could have been groups of different Jews," said Robert Cargill, an archaeologist who appears in the documentary Writing the Dead Sea Scrolls, which airs Tuesday at 9 p.m. ET/PT on the National Geographic Channel.
The new view is by no means the consensus, however, among Dead Sea Scrolls scholars.
"I have a feeling it's going to be very disputed," said Lawrence Schiffman, a professor of Hebrew and Judaic Studies at New York University (NYU).
Dead Sea Scrolls Written by Ritual Bathers?
In 1953, a French archaeologist and Catholic priest named Roland de Vaux led an international team to study the mostly Hebrew scrolls, which a Bedouin shepherd had discovered in 1947.
De Vaux concluded that the scrolls' authors had lived in Qumran, because the 11 scroll caves are close to the site.
Ancient Jewish historians had noted the presence of Essenes in the Dead Sea region, and de Vaux argued Qumran was one of their communities after his team uncovered numerous remains of pools that he believed to be Jewish ritual baths.
His theory appeared to be supported by the Dead Sea Scrolls themselves, some of which contained guidelines for communal living that matched ancient descriptions of Essene customs.
"The scrolls describe communal dining and ritual bathing instructions consistent with Qumran's archaeology," explained Cargill, of the University of California, Los Angeles (UCLA).
Dead Sea Scrolls: "Great Treasure From the Temple"?
Recent findings by Yuval Peleg, an archaeologist who has excavated Qumran for 16 years, are challenging long-held notions of who wrote the Dead Sea Scrolls.
Artifacts discovered by Peleg's team during their excavations suggest Qumran once served as an ancient pottery factory. The supposed baths may have actually been pools to capture and separate clay.
And on Jerusalem's Mount Zion, archaeologists recently discovered and deciphered a two-thousand-year-old cup with the phrase "Lord, I have returned" inscribed on its sides in a cryptic code similar to one used in some of the Dead Sea Scrolls.
To some experts, the code suggests that religious leaders from Jerusalem authored at least some of the scrolls.
"Priests may have used cryptic texts to encode certain texts from nonpriestly readers," Cargill told National Geographic News.
According to an emerging theory, the Essenes may have actually been Jerusalem Temple priests who went into self-imposed exile in the second century B.C., after kings unlawfully assumed the role of high priest.
This group of rebel priests may have escaped to Qumran to worship God in their own way. While there, they may have written some of the texts that would come to be known as the Dead Sea Scrolls.
The Essenes may not have abandoned all of their old ways at Qumran, however, and writing in code may have been one of the practices they preserved.
It's possible too that some of the scrolls weren't written at Qumran but were instead spirited away from the Temple for safekeeping, Cargill said.
"I think it dramatically changes our understanding of the Dead Sea Scrolls if we see them as documents produced by priests," he says in the new documentary.
"Gone is the Ark of the Covenant. We're never going to find Noah's Ark, the Holy Grail. These things, we're never going to see," he added. "But we just may very well have documents from the Temple in Jerusalem. It would be the great treasure from the Jerusalem Temple."
Dead Sea Scrolls From Far and Wide?
Many modern archaeologists such as Cargill believe the Essenes authored some, but not all, of the Dead Sea Scrolls.
Recent archeological evidence suggests disparate Jewish groups may have passed by Qumran around A.D. 70, during the Roman siege of Jerusalem, which destroyed the Temple and much of the rest of the city.
A team led by Israeli archaeologist Ronnie Reich recently discovered ancient sewers beneath Jerusalem. In those sewers they found artifacts—including pottery and coins—that they dated to the time of the siege. (Related: "Underground Tunnels Found in Israel Used In Ancient Jewish Revolt.")
The finds suggest that the sewers may have been used as escape routes by Jews, some of whom may have been smuggling out cherished religious scrolls, according to Writing the Dead Sea Scrolls.
Importantly, the sewers lead to the Valley of Kidron. From there it's only a short distance to the Dead Sea—and Qumran.
The jars in which the scrolls were found may provide additional evidence that the Dead Sea Scrolls are a collection of disparate sects' texts.
Jan Gunneweg of Hebrew University in Jerusalem performed chemical analysis on vessel fragments from the Qumran-area caves.
"We take a piece of ceramic, we grind it, we send it to a nuclear reactor, where it's bombarded with neutrons, then we can measure the chemical fingerprint of the clay of which the pottery was made," Gunneweg says in the documentary.
"Since there is no clay on Earth with the exact chemical composition—it is like DNA—you can point to a specific area and say this pottery was made here, that pottery was made over here."
Gunneweg's conclusion: Only half of the pottery that held the Dead Sea Scrolls is local to Qumran.
Scroll Theory "Rejected by Everyone"
Not everyone agrees with the idea that Dead Sea Scrolls may hail from beyond Qumran.
"I don't buy it," said NYU's Schiffman, who added that the idea of the scrolls being written by multiple Jewish groups from Jerusalem has been around since the 1950s.
"The Jerusalem theory has been rejected by virtually everyone in the field," he said.
"The notion that someone brought a bunch of scrolls together from some other location and deposited them in a cave is very, very unlikely," Schiffman added.
"The reason is that most of the [the scrolls] fit a coherent theme and hang together.
"If the scrolls were brought from some other place, presumably by some other groups of Jews, you would expect to find items that fit the ideologies of groups that are in disagreement with [the Essenes]. And it's not there," said Schiffman, who dismisses interpretations that link some Dead Sea Scroll writings to groups such as the Zealots.
UCLA's Cargill agrees with Schiffman that the Dead Sea Scrolls show "a tremendous amount of congruence of ideology, messianic expectation, interpretation of scripture, [Jewish law] interpretation, and calendrical dates.
"At the same time," Cargill said, "it is difficult to explain some of the ideological diversity present within some of the scrolls if one argues that all of the scrolls were composed by a single sectarian group at Qumran."
Caves Were for Temporary Scroll Storage?
If Cargill and others are correct, it would mean that what modern scholars call the Dead Sea Scrolls are not wholly the work of isolated scribes.
Instead they may be the unrecovered treasures of terrified Jews who did not—or could not—return to reclaim what they entrusted to the desert for safekeeping.
"Whoever wrote them, the scrolls were considered scripture by their owners, and much care was taken to ensure their survival," Cargill said.
"Essenes or not, the Dead Sea Scrolls give us a rare glimpse into the vast diversity of Judaism—or Judaisms—in the first century."
Publicado por Nathaniel en 9:37 No hay comentarios:
Rocks on Mars May Provide Link to Evidence of Living Organisms Roughly 4 Billion Years Ago
A new article in press of the journal Earth and Planetary Science Letters unveils groundbreaking research on the hydrothermal formation of Clay-Carbonate rocks in the Nili Fossae region of Mars. The findings may provide a link to evidence of living organisms on Mars, roughly 4 billion years ago in the Noachian period.
The paper -- by Adrian J. Brown of the SETI Institute and colleagues at NASA's Jet Propulsion Laboratory, Johns Hopkins University Applied Physics Laboratory, the Desert Research Institute and Brazil's Universidade Estadual de Campinas -- analyzes data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), using co-located HiRISE images in order to further characterize the rocks.
The researchers suggest that carbonate bearing rocks found in the Nili Fossae region of Mars are made up of hydrothermally altered ultramafic (perhaps komatiitic) rocks. It also shows that the carbonates at Nili Fossae are not pure Mg-carbonate. Moreover, the study explains that talc is present in close proximity to the carbonate locations -- rather than previously suggested saponite -- and talc-carbonate alteration of high-Mg precursor rocks has taken place.
Brown explains: "We suggest that the associated hydrothermal activity would have provided sufficient energy for biological activity on early Mars at Nili Fossae. Furthermore, in the article we discuss the potential of the Archean volcanics of the East Pilbara region of Western Australia as an analog for the Nochian Nili Fossae on Mars. They indicate that biomarkers or evidence of living organisms, if produced at Nili, could have been preserved, as they have been in the North Pole Dome region of the Pilbara craton."
The discovery, remarked Tilman Spohn, editor of Earth and Planetary Sciences, "marks a significant finding in the Nili Fossae region of Mars, highlighting similarities between traces of life on early Earth and early Mars, and suggests a landing site for an exobiology mission to Mars."
The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Elsevier, via AlphaGalileo.
Publicado por Nathaniel en 9:34 No hay comentarios:
Signs of Reversal of Arctic Cooling: Rapid Temperature Rise in the Coldest Region of Mainland Europe
Parts of the Arctic have cooled over the past century, but temperatures have been rising steeply since 1990. This is the finding of a summer temperature reconstruction for the past 400 years produced on the base of tree rings from regions beyond the Arctic Circle.
German and Russian researchers analysed tree growth using ring width of pine from Russia's Kola Peninsula and compared their findings with similar studies from other parts of the Arctic. For the past 400 years since AD 1600, the reconstructed summer temperature on Kola in the months of July and August has varied between 10.4°C (1709) and 14.7°C (1957), with a mean of 12.2°C. Afterwards, after a cooling phase, a ongoing warming can be observed from 1990 onwards.
Researchers from the Institute of Geography in Moscow, Hohenheim University and the Helmholtz Centre for Environmental Research (UFZ) report in journal Arctic, Antarctic and Alpine Research: "The data indicate that solar activity may have been one of the major driving factors of summer temperatures, but this has been overlaid by other factors since 1990."
The researchers used for this study wood samples from a total of 69 Scots pines (Pinus sylvestris) from the Khibiny Mountains on the Kola Peninsula, situated between the Arctic Circle and the ocean port of Murmansk, not far from the Finnish border. The investigated region is a transition zone between Scandinavia, which is strongly affected by the gulf stream resp. North Atlantic Current, and the continental regions Eurasia. This makes the region particularly interesting for climatological studies.
Kola has a cold-temperate climate with long, moderately cold winters and cool, humid summers. In this part of the Arctic, the mean temperature fluctuates between -12°C in January and +13°C in July, with a growing season of just 60 to 80 days. The northern taiga vegetation is dominated by spruce, pine and birch. The samples came from three locations in the Khibiny Mountains close to recent altitudinal timberline at altitudes of between 250 and 450 m above sea level. The geographical northern timberline lies approximately 100 km further north.
In earlier studies, researchers led by Tatjana Böttger from the UFZ were able to show that pine forests on the Kola Peninsula expanded between 7000 and 3500 years ago to about 50 km north of their present-day limit.
However, for this study, they used trees from the altitudinal timberline, since they respond very sensitively to temperature fluctuations and provide particularly useful information, as demonstrated by US researchers in November 2009 in the journal PNAS when they used a long-lived species of pine in California and Nevada to show that these trees had grown particularly fast over the last 50 of the past 3500 years because of higher temperatures.
In the Tree-Ring-Laboratory at the University of Hohenheim in Stuttgart the German researchers measured the width of the individual tree rings. The calibration of these data with the help of meteorological records for the last 127 years and the interpretation of results occurred together with Russian Academy of Sciences in Moscow and the Helmholtz Centre for Environmental Research in Halle. "Besides of temperature, growth is also strongly influenced by non-climatic factors like light, nutrients, water supply and competition from other trees. So it is vital to isolate these trends to obtain a climate signal as pure as possible," explains Yury M. Kononov from the Russian Academy of Sciences in Moscow.
Following the summer temperature reconstruction on the Kola Peninsula, the researchers compared their results with similar tree-ring studies from Swedish Lapland and from the Yamal and Taimyr Peninsulas in Russian Siberia, which had been published in Holocene in 2002. The reconstructed summer temperatures of the last four centuries from Lapland and the Kola and Taimyr Peninsulas are similar in that all three data series display a temperature peak in the middle of the twentieth century, followed by a cooling of one or two degrees. Only the data series from the Yamal Peninsula differed, reaching its peak later, around 1990. What stands out in the data from the Kola Peninsula is that the highest temperatures were found in the period around 1935 and 1955, and that by 1990 the curve had fallen to the 1870 level, which corresponds to the start of the Industrial Age.
Since 1990, however, temperatures have increased again evidently. What is conspicuous about the new data is that the reconstructed minimum temperatures coincide exactly with times of low solar activity. The researchers therefore assume that in the past, solar activity was a significant factor contributing to summer temperature fluctuations in the Arctic. However, this correlation is only visible until 1970, after which time other -- possibly regional -- factors gain the upper hand. "One thing is certain: this part of the Arctic warmed up after the end of the Little Ice Age around 250 years ago, cooled down from the middle of the last century and has been warming up again since 1990," says Dr Tatjana Böttger, a paleoclimatologist at the UFZ.
In September 2009, another international team presented model calculations showing that the Arctic had gradually cooled down by around 0.2 °C per thousand years over the last two millennia to the start of the Industrial Age. They attributed this to a gradual decline in solar radiation in the summer. However, the last decade was the warmest of the Common Era and was 1.4 °C above the forecasts, report Darrell S. Kaufman and his colleagues in Science. The new data produced by Kononov, Friedrich and Böttger support the thesis that solar activity seems to be a significant factor influencing summer temperatures in the Arctic, but that its influence has weakened considerably over the past few decades.
Publicado por Nathaniel en 9:32 No hay comentarios:
Accepted Theory Explaining Frequent Eruptions at Italy’s Stromboli Volcano Questioned
Understanding the processes that cause volcanic eruptions can help scientists predict how often and how violently a volcano will erupt. Although scientists have a general idea of how these processes work -- the melting of magma below the volcano causes liquid magma and gases to force their way to Earth's surface -- eruptions happen so rarely, and often with little warning, that it can be difficult to study them in detail.
One volcano that volcanologists believe they understand fairly well is Italy's Stromboli, which has been erupting every five to 20 minutes for thousands of years, spewing fountains of ash and magma several meters into the sky. For several decades, scientists have pretty much used one theory to explain what is causing huge amounts of gas to erupt so frequently: swimming-pool-sized bubbles that travel through a few hundred meters of molten magma before popping at the surface.
But they may be wrong, according to new research by Jenny Suckale, a graduate student in MIT's Department of Earth, Atmospheric and Planetary Sciences (EAPS), who has developed a sophisticated computer model to simulate Stromboli's magma flow. In a two-paper series published July 20 in The Journal of Geophysical Research, Suckale suggests that giant gas bubbles can't be driving the Stromboli eruptions because such bubbles aren't compatible with the basic laws of fluid dynamics, or the science of how fluids move. Instead of large bubbles that pop at the top of Stromboli's conduits -- pipelike openings that connect the volcano's magma chamber to the Earth's surface -- Suckale thinks that the eruptions are caused by a spongelike plug located within the conduit, similar to a cork in a champagne bottle, that fractures every few minutes as a result of pressure created by significantly smaller bubbles.
Although all volcanoes are different -- some are driven by gas while others are driven by rising magma or interactions with water -- Suckale says that figuring out Stromboli would be "an important step forward for volcanology" because scientists don't really know the details of how most volcanoes function. Rethinking how Stromboli works could also shed light on the processes of volcanoes that appear to be driven by similar mechanisms as Stromboli, such as Mount Erebus in Antarctica, which has been continuously active since the 1970s.
Despite having a wealth of data about Stromboli, volcanologists have really only applied one model to explain Stromboli's continuous eruptions, Suckale says. According to the so-called "big bubble paradigm," as magma rises to Stromboli's surface, pressure drops, and this creates gas bubbles that merge together and can become several meters wide. Eventually, these bubbles explode at the top of the conduit.
But the problem with this theory, according to Suckale, is that it conflicts with the basic principles of fluid dynamics. Specifically, magma doesn't have enough surface tension (created when two fluids meet) or viscosity (a measure of a fluid's resistance) to maintain bubbles larger than a few dozen centimeters. She thinks that many researchers have assumed that bubbles inside Stromboli behave similarly to bubbles in a tank of water. "People take lab models as an analog for the volcano, but the scale is so different, and fluid dynamics is so dependent on scale," she explains.
To test the theory, Suckale and co-authors and EAPS professors Brad Hager and Lindy Elkins-Tanton, as well as Jean-Christophe Nave, a lecturer in MIT's Department of Mathematics, developed a computer model of the inner volcano's mixture of gas and magma and the bubbles that can rupture or merge. By changing certain parameters, such as scale, she discovered that it would be physically impossible for massive gas bubbles in Stromboli to survive for longer than a second because of the lack of stabilizing forces, such as surface tension and viscosity.
Suckale still believes there are gas bubbles inside Stromboli that are created by some unknown source located underneath the volcano. But she thinks these bubbles are significantly smaller -- perhaps only several centimeters thick -- and accumulate beneath a porous plug that covers part of the volcano. As the bubbles exert greater pressure on the plug, it eventually fractures, causing gas, rocks and liquid to scatter into the sky. This could explain why samples of Stromboli rock contain many tiny crystals -- because the top of Stromboli is a spongelike plug of crystals and gas bubbles that releases lots of gas every few minutes.
Kathy Cashman, a geologist at the University of Oregon, says Suckale's modeling work "greatly advances" volcanologists' understanding of the bubbles inside Stromboli and may also shed light on noneruptive processes in volcanoes that could also be transferring gas to the atmosphere. "Jenny's work sits at the boundary of these two types of gas transfer, and her modeling may help to address very fundamental issues related to volatile budgets of both the magma and the atmosphere," Cashman says. But she cautions that Suckale's work represents a "first step" toward modeling a very complex system, and that future modeling efforts should address the effect that crystals may have on bubble behavior.
Suckale agrees, but for now, she is working to develop a new model to explain how she thinks the theorized Stromboli plug works, why it could cause such constant eruptions and what this might say about other volcanoes that erupt frequently.
Publicado por Nathaniel en 9:31 No hay comentarios:
Brown Dwarf Found Orbiting a Young Sun-Like Star
Astronomers have imaged a very young brown dwarf, or failed star, in a tight orbit around a young nearby sun-like star.
An international team led by University of Hawaii astronomers Beth Biller and Michael Liu with help from University of Arizona astronomer Laird Close and UA graduate students Eric Nielsen, Jared Males and Andy Skemer made the rare find using the Near-Infrared Coronagraphic Imager, or NICI, on the international 8-meter Gemini-South Telescope in Chile.
What makes this discovery special is the proximity between the 36 Jupiter-mass brown dwarf companion, dubbed PZ Tel B, and its primary star, named PZ Tel A. They are separated by only 18 Astronomical Units, or AUs, similar to the distance between Uranus and the sun.
Most young brown dwarf and planetary companions found by direct imaging are at orbital separations greater than 50 AUs -- larger than the orbit of Pluto, at 40 AUs.
In addition to its small separation, in just the past year the researchers observed PZ Tel B moving quickly outward from its parent star.
An older image, taken seven years ago and reanalyzed by Laird Close, a professor at UA's Steward Observatory and the department of astronomy, showed PZ Tel B was obscured by the glare from its parent star as recently as 2003, indicating its orbit is more elliptical than circular.
"Because PZ Tel A is a rare star being both close and very young, it had been imaged several times in the past," said Close. "So we were quite surprised to see a new companion around what was thought to be a single star."
Lead author and UA graduate Beth Biller said, "PZ Tel B travels on a particularly eccentric orbit -- in the last 10 years, we have literally watched it careen through its inner solar system. This can best be explained by a highly eccentric, or oval-shaped, orbit."
The host star, PZ Tel A, is a younger version of the sun, having a similar mass but a very young age of only 12 million years (about 400 times younger than the sun). In fact, the PZ Tel system is young enough to still possess significant amounts of cold circumstellar dust, which may have been sculpted by the gravitational interaction with the young brown dwarf companion.
This makes the PZ Tel system an important laboratory for studying the early stages of solar system formation. With an estimated mass of 36 times that of Jupiter, PZ Tel B's orbital motion has significant implications for what type of planets can form (and whether planets can form at all) in the PZ Tel system.
Because PZ Tel B is so close to its parent star, special techniques are necessary to distinguish the faint light of the companion from the light of the primary star. PZ Tel B is separated by 0.33 arcseconds from PZ Tel A, equivalent to a dime seen at a distance of 7 miles (11 km).
In order to take pictures so close to the star, the team used an adaptive optics system coupled to a coronagraph in order to block out excess starlight, and then applied specialized analysis techniques to the images to detect PZ Tel B and measure its orbital motion.
PZ Tel B was discovered using the Near-Infrared Coronagraphic Imager, or NICI, the most powerful high-contrast instrument designed for imaging brown dwarfs and extrasolar planets around other stars. NICI can detect companions 1 million times fainter than the host star at just 1 arcsecond separations.
An international team of researchers drawn from across the Gemini Telescope community is currently carrying out a 300-star survey with NICI, the largest high-contrast imaging survey conducted to date.
NICI campaign leader Michael Liu said: "We are just beginning to glean the many configurations of solar systems around stars like the sun. The unique capabilities of NICI provide us with a powerful tool for studying their constituents using direct imaging."
The discovery of PZ Tel B is described in a paper being published by Astrophysical Journal Letters.
This research was supported by grants from the National Science Foundation and NASA. NICI is a facility instrument at the Gemini Observatory.
Publicado por Nathaniel en 9:29 No hay comentarios:
viernes, 23 de julio de 2010
Buckyballs Found in Space
The discovery of these carbon structures in space could have a profound impact on our understanding of chemistry in the cosmos.
Scientists have found crystalline forms of carbon -- spheres comprised of 60- and 70-atom clusters -- in a planetary nebula.
Carbon in this form is known as a buckminsterfullerene and was discovered in 1985.
Buckyballs and related spherical cages of carbon molecules sired the field of nanotechnology.
Twenty-five years after the discovery of buckyballs, the 60-packs of carbon molecules are found again -- this time in space, baked into the death shroud of a sun-like star.
The finding promises to open new doors in astronomy, just as the 1985 discovery of the third form of solid carbon (after diamond and graphite) revolutionized chemistry, leading to new materials built one stable molecule at a time.
The buckyballs were found in a planetary nebula called Tc 1, located about 6,000 light-years away. These types of nebula are shells of gas and dust shed by dying stars. In the case of Tc 1, the star, now a white dwarf, is still encased, but not quite dead.
Astronomers believe that as recently as 100 years ago, the star had another outburst. Its layers of hydrogen, however, already had been shed, leaving it with a helium shell and carbon-rich core.
"For a lot of planetary nebulae, that may be an end stage. But then the helium shell started burning, and it shed carbon-rich and hydrogen-poor material," lead researcher Jan Cami with the University of Western Ontario in Canada told Discovery News.
That turned out to be an ideal environment for cooling carbon atoms to cluster into their most stable form, 60-atom molecules shaped like soccer balls, known as buckyballs.
Cami and colleagues found the molecules by looking at Tc 1's infrared emissions with NASA's Spitzer Space Telescope.
When light hits molecules and atoms, they will vibrate in specific, measurable ways -- a field of science known as spectroscopy. One of Cami's colleagues, who was studying Tc 1, found some unfamiliar fingerprints in the nebula's infrared light. Cami recognized them as carbon's 60-atom configuration and its favored 70-atom carbon partner.
"Cami's data is just so beautifully convincing. They have got some observations that there's almost nothing else interfering," Florida State University chemist Harold Kroto said in an interview.
In 1985, Kroto, with the University of Sussex in the United Kingdom at the time, and colleagues at Rice University in Texas were conducting laboratory experiments to try to understand how long chains of carbon molecules could be made. The carbon chains were found in interstellar space with radio telescopes in the 1970s.
They ended up discovering a third form of solid carbon, perfectly symmetrical geodesic spheres, which they named buckminsterfullerene after the American architect Buckminster Fuller. The most widely known fullerene is a buckyball -- 60 carbon atoms arranged by pentagons and hexagons into a hollow molecular cage one-billionth of a meter wide.
The discovery, which earned Kroto and colleagues Robert Curl and Richard Smalley the 1996 Nobel Prize in Chemistry, opened new frontiers in organic chemistry, physics, materials sciences and electronics.
The molecule proved a stable scaffold for creating new molecules that could hold and dispense electrical charges. Nanotechnology, the science of building materials one atom at a time, was born.
The finding of buckyballs in space may be similarly profound. Buckyballs, for example, may be responsible for mysterious sets of chemical fingerprints in the interstellar medium, known as the diffuse interstellar bands.
"Once you form fullerenes, it's hard to destroy them. They survive high energy, harsh radiation, even cosmic rays hitting them. They're very stable," Cami said. "This is actually just the beginning of a new research field."
The study is published in this week's issue of Science.
Publicado por Nathaniel en 8:09 No hay comentarios:
Crater Lake National Park
Established: May 22,1902
Size: 183,224 acres (74,148 hectares)
Few forget their first glimpse of Crater Lake on a clear summer's day—21 square miles (54 square kilometers) of water so intensely blue it looks like ink, ringed by cliffs towering up to 2,000 feet (610 meters) above. The mountain bluebird, Indian legend says, was gray before dipping into the waters.
The tranquil Gem of the Cascades is set in a dormant volcano called Mount Mazama, one in the chain of volcanoes that includes Mount St. Helens. Mount Mazama's eruption about 5700 B.C. catapulted volcanic ash miles into the sky and expelled so much pumice and ash that the summit soon collapsed, creating a huge, smoldering caldera.
Eventually, rain and snowmelt accumulated in the caldera, forming a lake more than 1,900 feet (580 meters) deep, the deepest lake in the United States. Wildflowers, along with hemlock, fir, and pine, recolonized surroundings. Black bears and bobcats, deer and marmots, eagles and hawks returned.
Scientists have yet to understand completely Crater Lake's ecology. In 1988 and 1989, using a manned submarine, they discovered evidence that proves hydrothermal venting exists on the lake's bottom and may play a role in the lake's character.
Crater Lake forms a superb setting for day hikes. Thanks to some of the cleanest air in the nation, you can see more than a hundred miles (160 kilometers) from points along many of the park's 90 miles (145 kilometers) of trails. Forests of mountain hemlock and Shasta red fir predominate near the caldera rim. At the rim twisted whitebark pines testify to the harshness of the long winter. Ponderosa pine, the park's largest tree, and lodgepole pine are common farther down from the rim.
How to Get There
Enter the park from the west (Medford, about 85 miles/137 kilometers away) or the south (Klamath Falls, about 65 miles/105 kilometers away) on Oreg. 62, or from the north on Oreg. 138. Airports: Medford and Klamath Falls.
When to Go
The lake best displays its dazzling color in summer. Oreg. 62 and the access road leading to Rim Village remain open in winter, and cross-country skiing is becoming increasingly popular. The drive around the lake usually closes in October because of snow; in some years, the drive may not reopen completely until mid-July. Peak wildflower viewing is late July/early August.
How to Visit
Spend at least a half day touring the 33-mile (53-kilometer) Rim Drive, enjoying its many overlooks and several hiking trails. On a second day, consider a hike down to the shore for the two hour narrated boat tour of the lake. Some tours stop at Wizard Island; if time and weather permit, climb to the top of it and catch a later boat back.
Publicado por Nathaniel en 8:07 No hay comentarios:
"Fresh" Crater Found in Egypt; Changes Impact Risk?
A small impact crater discovered in the Egyptian desert could change estimates for impact hazards to our planet, according to a new study.
One of the best preserved craters yet found on Earth, the Kamil crater was initially discovered in February during a survey of satellite images on Google Earth. Researchers think the crater formed within the past couple thousand years.
The Italian-Egyptian team that found the crater in pictures recently visited and studied the 147-foot-wide (45-meter-wide), 52-foot-deep (16-meter-deep) hole. The team also collected thousands of pieces of the space rock that littered the surrounding desert.
Based on their calculations, the team thinks that a 4.2-foot-wide (1.3-meter-wide) solid iron meteor weighing 11,023 to 22,046 pounds (5,000 to 10,000 kilograms) smashed into the desert—nearly intact—at speeds exceeding 2.1 miles (3.5 kilometers) a second.
There are no hard numbers for how many meteors this size might currently be on a collision course with Earth, but scientists think the potential threats could be in the tens of thousands.
Current impact models state that iron meteors around this size and mass should break into smaller chunks before impact.
Instead, the existence of the newfound crater implies that up to 35 percent of these iron giants may actually survive whole—and thus have greater destructive power.
Egypt Crater Still Shows Splatter
Estimating impact hazards to Earth isn't an exact science, since only 176 impact craters have been discovered so far, according to the Earth Impact Database, a resource maintained by the Geological Survey of Canada.
Most models are based on the number of impact craters on the moon, which has almost no atmosphere and so doesn't experience the same erosion processes as those on Earth.
"Current models predict that around a thousand to ten thousand such craters should have formed [on Earth] in one million years," said study co-author Luigi Folco, a scientist with the University of Siena in Italy.
"The reason why they are rare, however, is that, on Earth, weathering rates are high—small craters are usually easily eroded or buried."
Folco and colleagues were particularly surprised to find that the newfound, bowl-shaped crater has a prominent splatter pattern of bedrock shot up by the original impact blast.
Known as ejecta rays, these features are more often seen on other planets and moons with thin atmospheres.
The exact age of the Egyptian crater is still uncertain, the team reported this week in the online edition of the journal Science. Geologic evidence points to a relatively recent event, Folco said—although it's unlikely that any humans were around to witness the impact.
"During our field work we could see that some of the bedrock material ejected from the crater overlies prehistoric structures in the area," Folco said.
"We know from literature that the human occupation of this region ended about 5,000 years ago, with the onset of hyperarid conditions. Therefore we think that the impact occurred afterwards."
Meteor Threat Greater Than Realized
If future meteors like the Egyptian rock are more likely to remain intact, their energy on impact would be more focused, causing greater damage, said John Spray, a crater expert with the University of New Brunswick who isn't connected to the study.
Still, the probability of such a meteor hitting something critical for society, such as a major city, would be reduced, because the falling rocks would not be as spread out.
"Overall, the threat from impacts is probably greater than people realize, but historically there is very little information on this, and we just have not been collecting data for all that long," Spray said.
"Our knowledge is very limited, so events such as these are quite important for helping us understand the frequency and nature of impacts that affect our planet."
Publicado por Nathaniel en 7:59 No hay comentarios:
Hyperfast Star Was Booted from Milky Way
A hundred million years ago, a triple-star system was traveling through the bustling center of our Milky Way galaxy when it made a life-changing misstep. The trio wandered too close to the galaxy's giant black hole, which captured one of the stars and hurled the other two out of the Milky Way. Adding to the stellar game of musical chairs, the two outbound stars merged to form a super-hot, blue star.
This story may seem like science fiction, but astronomers using NASA's Hubble Space Telescope say it is the most likely scenario for a so-called hypervelocity star, known as HE 0437-5439, one of the fastest ever detected. It is blazing across space at a speed of 1.6 million miles (2.5 million kilometers) an hour, three times faster than our Sun's orbital velocity in the Milky Way. Hubble observations confirm that the stellar speedster hails from the Milky Way's core, settling some confusion over where it originally called home.
Most of the roughly 16 known hypervelocity stars, all discovered since 2005, are thought to be exiles from the heart of our galaxy. But this Hubble result is the first direct observation linking a high-flying star to a galactic center origin.
"Using Hubble, we can for the first time trace back to where the star comes from by measuring the star's direction of motion on the sky. Its motion points directly from the Milky Way center," says astronomer Warren Brown of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., a member of the Hubble team that observed the star. "These exiled stars are rare in the Milky Way's population of 100 billion stars. For every 100 million stars in the galaxy lurks one hypervelocity star."
The movements of these unbound stars could reveal the shape of the dark matter distribution surrounding our galaxy. "Studying these stars could provide more clues about the nature of some of the universe's unseen mass, and it could help astronomers better understand how galaxies form," says team leader Oleg Gnedin of the University of Michigan in Ann Arbor. "Dark matter's gravitational pull is measured by the shape of the hyperfast stars' trajectories out of the Milky Way."
The stellar outcast is already cruising in the Milky Way's distant outskirts, high above the galaxy's disk, about 200,000 light-years from the center. By comparison, the diameter of the Milky Way's disk is approximately 100,000 light-years. Using Hubble to measure the runaway star's direction of motion and determine the Milky Way's core as its starting point, Brown and Gnedin's team calculated how fast the star had to have been ejected to reach its current location.
"The star is traveling at an absurd velocity, twice as much as the star needs to escape the galaxy's gravitational field," explains Brown, a hypervelocity star hunter who found the first unbound star in 2005. "There is no star that travels that quickly under normal circumstances -- something exotic has to happen."
There's another twist to this story. Based on the speed and position of HE 0437-5439, the star would have to be 100 million years old to have journeyed from the Milky Way's core. Yet its mass -- nine times that of our Sun -- and blue color mean that it should have burned out after only 20 million years -- far shorter than the transit time it took to get to its current location.
The most likely explanation for the star's blue color and extreme speed is that it was part of a triple-star system that was involved in a gravitational billiard-ball game with the galaxy's monster black hole. This concept for imparting an escape velocity on stars was first proposed in 1988. The theory predicted that the Milky Way's black hole should eject a star about once every 100,000 years.
Brown suggests that the triple-star system contained a pair of closely orbiting stars and a third outer member also gravitationally tied to the group. The black hole pulled the outer star away from the tight binary system. The doomed star's momentum was transferred to the stellar twosome, boosting the duo to escape velocity from the galaxy. As the pair rocketed away, they went on with normal stellar evolution. The more massive companion evolved more quickly, puffing up to become a red giant. It enveloped its partner, and the two stars spiraled together, merging into one superstar -- a blue straggler.
"While the blue straggler story may seem odd, you do see them in the Milky Way, and most stars are in multiple systems," Brown says.
This vagabond star has puzzled astronomers since its discovery in 2005 by the Hamburg/European Southern Observatory sky survey. Astronomers had proposed two possibilities to solve the age problem. The star either dipped into the Fountain of Youth by becoming a blue straggler, or it was flung out of the Large Magellanic Cloud, a neighboring galaxy.
In 2008 a team of astronomers thought they had solved the mystery. They found a match between the exiled star's chemical makeup and the characteristics of stars in the Large Magellanic Cloud. The rogue star's position also is close to the neighboring galaxy, only 65,000 light-years away. The new Hubble result settles the debate over the star's birthplace.
Astronomers used the sharp vision of Hubble's Advanced Camera for Surveys to make two separate observations of the wayward star 3 1/2 years apart. Team member Jay Anderson of the Space Telescope Science Institute in Baltimore, Md., developed a technique to measure the star's position relative to each of 11 distant background galaxies, which form a reference frame.
Anderson then compared the star's position in images taken in 2006 with those taken in 2009 to calculate how far the star moved against the background galaxies. The star appeared to move, but only by 0.04 of a pixel (picture element) against the sky background. "Hubble excels with this type of measurement," Anderson says. "This observation would be challenging to do from the ground."
The team is trying to determine the homes of four other unbound stars, all located on the fringes of the Milky Way.
"We are targeting massive 'B' stars, like HE 0437-5439," says Brown, who has discovered 14 of the 16 known hypervelocity stars. "These stars shouldn't live long enough to reach the distant outskirts of the Milky Way, so we shouldn't expect to find them there. The density of stars in the outer region is much less than in the core, so we have a better chance to find these unusual objects."
The results were published online in The Astrophysical Journal Letters on July 20, 2010. Brown is the paper's lead author.
Now You See It, Now You Don't: An Infrared Invisibility Cloak Made of Glass
From Tolkien's ring of power in The Lord of the Rings to Star Trek's Romulans, who could make their warships disappear from view, from Harry Potter's magical cloak to the garment that makes players vanish in the video game classic "Dungeons and Dragons", the power to turn someone or something invisible fascinates humankind. But who ever thought that a scientist at Michigan Technological University would be serious about building a working invisibility cloak?
That's exactly what Elena Semouchkina, an associate professor of electrical and computer engineering at Michigan Tech, is doing. She has found ways to use magnetic resonance to capture rays of visible light and route them around objects, rendering those objects invisible to the human eye.
Semouchkina and colleagues at the Pennsylvania State University, where she is also an adjunct professor, recently reported on their research in the journal Applied Physics Letters, published by the American Institute of Physics. Her co-authors were Douglas Werner and Carlo Pantano of Penn State and George Semouchkin, who works at Michigan Tech and Penn State.
They describe developing a nonmetallic cloak that uses identical glass resonators made of chalcogenide glass, a type of dielectric material (one that does not conduct electricity). In computer simulations, the cloak made objects hit by infrared waves -- approximately one micron or one-millionth of a meter long -- disappear from view.
Earlier attempts by other researchers used metal rings and wires. "Ours is the first to do the cloaking of cylindrical objects with glass," Semouchkina said.
Her invisibility cloak uses metamaterials, which are artificial materials having properties that do not exist in nature, made of tiny glass resonators arranged in a concentric pattern in the shape of a cylinder. The "spokes" of the concentric configuration produce the magnetic resonance required to bend light waves around an object, making it invisible.
Metamaterials, which huse small resonators instead of atoms or molecules of natural materials, straddle the boundary between materials science and electrical engineering. They were named one of the top three physics discoveries of the decade by the American Physical Society. A new researcher specializing in metamaterials is joining Michigan Tech's faculty this fall.
Semouchkina and her team now are testing an invisibility cloak rescaled to work at mocrowave frequencies and made of ceramic resonators. They're using Michigan Tech's anechoic chamber, a cave-like compartment in an Electrical Energy Resources Center lab, lined with highly absorbent charcoal-gray foam cones. There, antennas transmit and receive microwaves, which are much longer than infrared light, up to several centimeters long. They have cloaked metal cylinders two to three inches in diameter and three to four inches high.
"Starting from these experiments, we want to move to higher frequencies and smaller wavelengths," the researcher said. "The most exciting applications will be at the frequencies of visible light."
So one day, could the police cloak a swat team or the Army, a tank? "It is possible in principle, but not at this time," Semouchkina said.
Her work is supported in part by a grant from the National Science Foundation.
Quantum Mechanics Not in Jeopardy: Physicists Confirm a Decades-Old Key Principle Experimentally
When waves -- regardless of whether light or sound -- collide, they overlap creating interferences. Austrian and Canadian quantum physicists have now been able to rule out the existence of higher-order interferences experimentally and thereby confirmed an axiom in quantum physics: Born's rule.
They have published their findings in the scientific journal Science.
In quantum mechanics many propositions are made in probabilities. In 1926 German physicist Max Born postulated that the probability to find a quantum object at a certain place at a certain time equals the square of its wave function. A direct consequence of this rule is the interference pattern as shown in the double slit diffraction experiment. Born's rule is one of the key laws in quantum mechanics and it proposes that interference occurs in pairs of possibilities. Interferences of higher order are ruled out. There was no experimental verification of this proposition until now, when the research group led by Prof. Gregor Weihs from the University of Innsbruck and the University of Waterloo has confirmed the accuracy of Born's law in a triple-slit experiment. "The existence of third-order interference terms would have tremendous theoretical repercussions -- it would shake quantum mechanics to the core," says Weihs. The impetus for this experiment was the suggestion made by physicists to generalize either quantum mechanics or gravitation -- the two pillars of modern physics -- to achieve unification, thereby arriving at a one all-encompassing theory. "Our experiment thwarts these efforts once again," explains Gregor Weihs.
Gregor Weihs -- Professor of Photonics at the University of Innsbruck -- and his team are investigating new light sources to be used for transmitting quantum information. He developed a single-photon source, which served as the basis for testing Born's rule. Photons were sent through a steel membrane mask which has three micrometer sized slits cut into it. Measurements were performed with the slits closed individually resulting in eight independent slit combinations. The data taken was then used to calculate whether Born's rule applies. "In principle, this experiment is very simple," says Gregor Weihs "and we were quite surprised to find that nobody hadn't performed this experiment before." However, the physicists were struggling with measurement errors, which they were eventually able to overcome during their two year long Sisyphean task. "Our measurements show that we can rule out the existence of third-order interference up to a certain bound," says a happy experimental physicist Weihs. His next step will be to considerably lower the bound with an improved experiment.
Master of light particles
The experiment was performed at the Institute for Quantum Computing at the University of Waterloo in Canada, where Prof. Gregor Weihs worked before his appointment at the University of Innsbruck. Since 2008 he has been setting up his own research group at the Institute for Experimental Physics in Innsbruck, which now comprises twelve group members. The group, whose members come from all over the world, investigates the development of novel single-photon sources and entangled photon pairs from semiconductor nanostructures. The researcher's ultimate goal is to integrate quantum optical experiments with functions on semiconductor chips.
Publicado por Nathaniel en 7:54 No hay comentarios:
jueves, 22 de julio de 2010
Bowls of Fingers, Baby Victims, More Found in Maya Tomb
Reeking of decay and packed with bowls of human fingers, a partly burned baby, and gem-studded teeth—among other artifacts—a newfound Maya king's tomb sounds like an overripe episode of Tales From the Crypt.
But the tightly sealed, 1,600-year-old burial chamber, found under a jungle-covered Guatemalan pyramid, is as rich with archaeological gold as it is with oddities, say researchers who announced the discovery Friday.
"This thing was like Fort Knox," said Brown University archaeologist Stephen Houston, who led the excavation in the ancient, overgrown Maya town of El Zotz.
Alternating layers of flat stones and mud preserved human bones, wood carvings, textiles, and other organic material to a surprising degree—offering a rare opportunity to advance Maya archaeology, experts say.
"Since [the artifacts] appear in a royal tomb, they may provide direct insights in the political economy of the divine kings that likely involved tribute and gifts," Vanderbilt University anthropologist Markus Eberl, who was not involved in the project, said via email.
Excavation leader Houston added, "we're looking at a glimpse of lost art forms."
Fingers, Teeth, and a Taste of Things to Come
The researchers found grisly deposits even before they reached the Maya tomb.
Almost every layer of mud above the tomb contained blood-red pottery filled with human fingers and teeth wrapped in decayed organic material—perhaps leaves.
The fingers and teeth were "perhaps a kind of food or symbolic meal offering," Houston speculated. "Sacred breads in [Mexico's] Yucatán are wrapped in such materials today."
In another bowl above the circa A.D. 350 to 400 tomb, the team found a partly burned baby. The bowls closest to the burial chamber were arranged like the Maya cosmos—the four cardinal compass points plus the center of world.
Dancing King and Child Sacrifices
"The chill of the morgue" and "a faint odor of decay" tempered the euphoria of the find when the team finally entered the tomb itself on May 29, Houston said.
Breaking though a side wall of the small tomb, excavators uncovered the remains of six children—a rarity among Maya burials. Nearby was an obsidian blade covered in a red residue that "may be blood," Houston said.
The arrangement suggests the children, some of them infants, may have been ritually sacrificed as the king was laid to rest. (Read about Maya rituals of sacrifice and worship.)
Why the children would have been killed is a mystery, said team member Andrew Scherer, a Brown University anthropologist.
But the youth of the victims hints that their value as sacrifices may have lain in their being, to Maya eyes, on the verge of personhood, Scherer said.
Dig leader Houston added, "[The fact] that at least four appear not to have been able yet fully to speak or walk may put them at that threshold of human existence."
The role of the king in his own burial may be slightly clearer.
The team found bell-like ornaments made of shells and "clappers" made of dog teeth, which were likely placed around the king's waist and legs, Houston said.
The same accessories are seen on performers in a ritual dance depicted in Maya art, suggesting that the king may have been "cast" as a dancer in the ceremony leading to his interment—despite the arthritic joints that give away his apparently advanced age.
Turtle King Tomb a "Gold Mine"
His teeth embedded with jewels, the buried king, Houston suspects, was the founder of a dynasty at El Zotz, in what's now the Petén region (satellite map) of Guatemala.
According to the partially deciphered hieroglyphics on the tomb walls, his name translates to perhaps Red Turtle or Great Turtle. More information about him may be gleaned from further study of hieroglyphics from the tomb, Houston said.
A small state with no more than a few thousand people, El Zotz lay to the west of Tikal, once among the biggest and most powerful Maya centers
The neighboring settlements, though, probably weren't best of friends. El Zotz was likely "supported by the enemies of Tikal in a way to keep a check on Tikal's territorial ambitions," Houston said.
More details on the nature of that relationship—and on El Zotz and Maya life in general—may await decoding in the turtle king's tomb. The excavation team's next steps include residue analysis as well as continued analysis, and reconstruction, of the tomb's textiles and other artifacts.
"This," Houston said, "could be a veritable gold mine of information."
Publicado por Nathaniel en 9:21 No hay comentarios:
Drilling Down to the Nanometer Depths of Leaves for Biofuels
By imaging the cell walls of a zinnia leaf down to the nanometer scale, energy researchers have a better idea about how to turn plants into biofuels.
In a paper appearing online in the journal Plant Physiology, a team from Lawrence Livermore led by Michael Thelen, in collaboration with researchers from Lawrence Berkeley National Lab and the National Renewable Energy Laboratory, has used four different imaging techniques to systematically drill down deep into the cells of Zinnia elegans.
Zinnia is a common garden annual plant with solitary daisy like flower heads on long stems and sandpapery, lace shaped leaves. The leaves of seedlings provide a rich source of single cells that are dark green with chloroplasts and can be cultured in liquid for several days at a time. During the culturing process, the cells change in shape to resemble the tube-like cells that carry water from roots to leaves. Known as xylem, these cells hold the bulk of cellulose and lignin in plants, which are both major targets of recent biofuel research.
Using different microscopy methods, the team was able to visualize single cells in detail, cellular substructures, fine-scale organization of the cell wall, and even chemical composition of single zinnia cells, indicating that they contain an abundance of lignocellulose.
"The basic idea is that cellulose is a polymer of sugars, which if released by enzymes, can be converted into alcohols and other chemicals used in alternative fuel production," Thelen said. "But for this to happen efficiently, we need to find ways to see how this is proceeding at several spatial scales."
To get at the sugars is no easy task. The team had to find ways to overcome the hydrophobic protection of crystalline cellulose provided by lignin in the cell wall. The two polymers, collectively called lignocellulose, are very insoluble, resistant to common chemicals and mechanical breakage, and are a superior substance for providing strength and structure to plants.
The detailed three-dimensional molecular cell wall structure of plants remains poorly understood.
"The capability to image plant cell surfaces at the nanometer scale, together with the corresponding chemical composition, could significantly enhance our understanding of cell wall molecular architecture," said Alex Malkin, a member of the LLNL team who is an expert in atomic force microscopy. "A high resolution structural model is crucial for the successful implementation of new approaches for conversion of biomass to liquid fuels."
To make fuels from plant biomass requires a thorough understanding of the organization of cell walls before determining the best methods for cell wall deconstruction into its components. Catherine Lacayo, a postdoctoral scientist working with Thelen and Malkin, has taken the first steps toward a comprehensive approach.
She came up with techniques that reveal the inner structure of cell walls in these single xylem cells, which represent about 70 percent of the cellulose in plants that can be used in fuel processing. "This approach will be useful for evaluating the responses of plant material to various chemical and enzymatic treatments, and could accelerate the current efforts in lignocellulosic biofuel production."
The research is supported by the Department of Energy Genome Sciences Program through the Office of Biological and Environmental Research, and the DOE's BioEnergy Research Centers in Emeryville and Oak Ridge. It will appear in the September issue of Plant Physiology.
Publicado por Nathaniel en 9:19 No hay comentarios:
Cassini Sees Moon Building Giant Snowballs in Saturn Ring
While orbiting Saturn for the last six years, NASA's Cassini spacecraft has kept a close eye on the collisions and disturbances in the gas giant's rings. They provide the only nearby natural laboratory for scientists to see the processes that must have occurred in our early solar system, as planets and moons coalesced out of disks of debris.
New images from Cassini show icy particles in Saturn's F ring clumping into giant snowballs as the moon Prometheus makes multiple swings by the ring. The gravitational pull of the moon sloshes ring material around, creating wake channels that trigger the formation of objects as large as 20 kilometers (12 miles) in diameter.
"Scientists have never seen objects actually form before," said Carl Murray, a Cassini imaging team member based at Queen Mary, University of London. "We now have direct evidence of that process and the rowdy dance between the moons and bits of space debris."
Murray discussed the findings July 20 at the Committee on Space Research meeting in Bremen, Germany, and they are published online by the journal Astrophysical Journal Letters on July 14, 2010. A new animation based on imaging data shows how one of the moons interacts with the F ring and creates dense, sticky areas of ring material.
Saturn's thin, kinky F ring was discovered by NASA's Pioneer 11 spacecraft in 1979. Prometheus and Pandora, the small "shepherding" moons on either side of the F ring, were discovered a year later by NASA's Voyager 1. In the years since, the F ring has rarely looked the same twice, and scientists have been watching the impish behavior of the two shepherding moons for clues.
Prometheus, the larger and closer to Saturn of the two moons, appears to be the primary source of the disturbances. At its longest, the potato-shaped moon is 148 kilometers (92 miles) across. It cruises around Saturn at a speed slightly greater than the speed of the much smaller F ring particles, but in an orbit that is just offset. As a result of its faster motion, Prometheus laps the F ring particles and stirs up particles in the same segment once in about every 68 days.
"Some of these objects will get ripped apart the next time Prometheus whips around," Murray said. "But some escape. Every time they survive an encounter, they can grow and become more and more stable."
Cassini scientists using the ultraviolet imaging spectrograph previously detected thickened blobs near the F ring by noting when starlight was partially blocked. These objects may be related to the clumps seen by Murray and colleagues.
The newly-found F ring objects appear dense enough to have what scientists call "self-gravity." That means they can attract more particles to themselves and snowball in size as ring particles bounce around in Prometheus's wake, Murray said. The objects could be about as dense as Prometheus, though only about one-fourteenth as dense as Earth.
What gives the F ring snowballs a particularly good chance of survival is their special location in the Saturn system. The F ring resides at a balancing point between the tidal force of Saturn trying to break objects apart and self-gravity pulling objects together. One current theory suggests that the F ring may be only a million years old, but gets replenished every few million years by moonlets drifting outward from the main rings. However, the giant snowballs that form and break up probably have lifetimes of only a few months.
The new findings could also help explain the origin of a mysterious object about 5 to 10 kilometers (3 to 6 miles) in diameter that Cassini scientists spotted in 2004 and have provisionally dubbed S/2004 S 6. This object occasionally bumps into the F ring and produces jets of debris.
"The new analysis fills in some blanks in our solar system's history, giving us clues about how it transformed from floating bits of dust to dense bodies," said Linda Spilker, Cassini project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "The F ring peels back some of the mystery and continues to surprise us."
The late Kevin Beurle was made the honorary first author on this paper because of his contributions in developing software and designing observation sequences for this research. He died in 2009.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.
Publicado por Nathaniel en 9:18 No hay comentarios:
Finding Frugal Aliens: 'Benford Beacons' Concept Could Refocus Search for Signs of Intelligent Extraterrestrial Life
For 50 years, humans have scanned the skies with radio telescopes for distant electronic signals indicating the existence of intelligent alien life. The search -- centered at the SETI Institute in Mountain View, Calif. -- has tapped into our collective fascination with the concept that we may not be alone in the universe.
But the effort has so far proved fruitless, and the scientific community driving the SETI project has begun questioning its methodology, which entails listening to specific nearby stars for unusual blips or bleeps. Is there a better approach?
UC Irvine astrophysicist Gregory Benford and his twin, James -- a fellow physicist specializing in high-powered microwave technology -- believe there is, and their ideas are garnering attention.
In two studies appearing in the June issue of the journal Astrobiology, the Benford brothers, along with James' son Dominic, a NASA scientist, examine the perspective of a civilization sending signals into space -- or, as Gregory Benford puts it, "the point of view of the guys paying the bill."
"Our grandfather used to say, 'Talk is cheap, but whiskey costs money,'" the physics professor says. "Whatever the life form, evolution selects for economy of resources. Broadcasting is expensive, and transmitting signals across light-years would require considerable resources."
Assuming that an alien civilization would strive to optimize costs, limit waste and make its signaling technology more efficient, the Benfords propose that these signals would not be continuously blasted out in all directions but rather would be pulsed, narrowly directed and broadband in the 1-to-10-gigahertz range.
"This approach is more like Twitter and less like War and Peace, " says James Benford, founder and president of Microwave Sciences Inc. in Lafayette, Calif.
Their concept of short, targeted blips -- dubbed "Benford beacons" by the science press -- has gotten extensive coverage in such publications as Astronomy Now. Well-known cosmologist Paul Davies, in his 2010 book The Eerie Silence: Renewing Our Search for Alien Intelligence, supports the theory.
This means that SETI -- which focuses its receivers on narrow-band input -- may be looking for the wrong kind of signals. The Benfords and a growing number of scientists involved in the hunt for extraterrestrial life advocate adjusting SETI receivers to maximize their ability to detect direct, broadband beacon blasts.
But where to look? The Benfords' frugal-alien model points to our own Milky Way galaxy, especially the center, where 90 percent of its stars are clustered.
"The stars there are a billion years older than our sun, which suggests a greater possibility of contact with an advanced civilization than does pointing SETI receivers outward to the newer and less crowded edge of our galaxy," Gregory Benford says.
"Will searching for distant messages work? Is there intelligent life out there? The SETI effort is worth continuing, but our common-sense beacons approach seems more likely to answer those questions."
Publicado por Nathaniel en 9:17 No hay comentarios:
Cometary Impact on Neptune: Herschel Data Point to Collision About Two Centuries Ago
A comet may have hit the planet Neptune about two centuries ago. This is indicated by the distribution of carbon monoxide in the atmosphere of the gas giant that researchers -- among them scientists from the French obser-vatory LESIA in Paris, from the Max Planck Institute for Solar System Re-search (MPS) in Katlenburg-Lindau (Germany) and from the Max Planck Insti-tute for Extraterrestrial Physics in Garching (Germany) -- have now studied. The scientists analyzed data taken by the research satellite Herschel, that has been orbiting the Sun in a distance of approximately 1.5 million kilometers since May 2009.
The research is published in Astronomy & Astrophysics (July 16, 2010).
When the comet Shoemaker-Levy 9 hit Jupiter sixteen years ago, scientists all over the world were prepared: instruments on board the space probes Voyager 2, Galileo and Ulysses documented every detail of this rare incident. Today, this data helps scientists detect cometary impacts that happened many, many years ago. The "dusty snowballs" leave traces in the atmosphere of the gas giants: water, carbon dioxide, carbon monoxide, hydrocyanic acid, and carbon sulfide. These molecules can be detected in the radiation the planet radiates into space.
In February 2010 scientists from Max Planck Institute for Solar System Research discovered strong evidence for a cometary impact on Saturn about 230 years ago (see Astronomy and Astrophysics, Volume 510, February 2010). Now new measurements performed by the instrument PACS (Photodetector Array Camera and Spectrometer) on board the Herschel space observatory indicate that Neptune experienced a similar event. For the first time, PACS allows researchers to analyze the long-wave infrared radiation of Neptune.
The atmosphere of the outer-most planet of our solar system mainly consists of hydrogen and helium with traces of water, carbon dioxide and carbon monoxide. Now, the scientists detected an unusual distribution of carbon monoxide: In the upper layer of the atmosphere, the so-called stratosphere, they found a higher concentration than in the layer beneath, the troposphere. "The higher concentration of carbon monoxide in the stratosphere can only be explained by an external origin," says MPS-scientist Paul Hartogh, principle investigator of the Herschel science program "Water and related chemistry in the solar system." "Normally, the concentrations of carbon monoxide in troposphere and stratosphere should be the same or decrease with increasing height," he adds.
The only explanation for these results is a cometary impact. Such a collision forces the comet to fall apart while the carbon monoxide trapped in the comet's ice is released and over the years distributed throughout the stratosphere. "From the distribution of carbon monoxide we can therefore derive the approximate time, when the impact took place," explains Thibault Cavalié from MPS. The earlier assumption that a comet hit Neptune two hundred years ago could thus be confirmed. A different theory according to which a constant flux of tiny dust particles from space introduces carbon monoxide into Neptune's atmosphere, however, does not agree with the measurements.
In Neptune's stratosphere the scientists also found a higher concentration of methane than expected. On Neptune, methane plays the same role as water vapor on Earth: the temperature of the so-called tropopause -- a barrier of colder air separating troposphere and stratosphere -- determines how much water vapor can rise into the stratosphere. If this barrier is a little bit warmer, more gas can pass through. But while on Earth the temperature of the tropopause never falls beneath minus 80 degrees Celsius, on Neptune the tropopause's mean temperature is minus 219 degrees.
Therefore, a gap in the barrier of the tropopause seems to be responsible for the elevated concentration of methane on Neptune. With minus 213 degrees Celsius, at Neptune's southern Pole this air layer is six degrees warmer than everywhere else allowing gas to pass more easily from troposphere to stratosphere. The methane, which scientists believe originates from the planet itself, can therefore spread throughout the stratosphere.
The instrument PACS was developed at the Max Planck Institute for Extraterrestrial Physics. It analyzes the long-wave infrared radiation, also known as heat radiation, that the cold bodies in space such as Neptune emit. In addition, the research satellite Herschel carries the largest telescope ever to have been operated in space.
Publicado por Nathaniel en 9:15 No hay comentarios:
Black Hole Jerked Around Twice
Scientists have found evidence that a giant black hole has been jerked around twice, causing its spin axis to point in a different direction from before. This discovery, made with new data from NASA's Chandra X-ray Observatory, might explain several mysterious-looking objects found throughout the Universe.
The axis of the spinning black hole is thought to have moved, but not the black hole itself, so this result differs from recently published work on recoiling black holes.
"We think this is the best evidence ever seen for a black hole having been jerked around like this," said Edmund Hodges-Kluck of the University of Maryland. "We're not exactly sure what caused this behavior, but it was probably triggered by a collision between two galaxies."
A team of astronomers used Chandra for a long observation of a galaxy known as 4C+00.58, which is located about 780 million light years from Earth. Like most galaxies, 4C+00.58 contains a supermassive black hole at its center, but this one is actively pulling in copious quantities of gas. Gas swirling toward the black hole forms a disk around the black hole. Twisted magnetic fields in the disk generate strong electromagnetic forces that propel some of the gas away from the disk at high speed, producing radio jets.
A radio image of this galaxy shows a bright pair of jets pointing from left to right and a fainter, more distant line of radio emission running in a different direction. More specifically, 4C+00.58 belongs to a class of "X-shaped" galaxies, so called because of the outline of their radio emission.
The new Chandra data have allowed astronomers to determine what may be happening in this system, and perhaps in others like it. The X-ray image reveals four different cavities around the black hole. These cavities come in pairs: one in the top-right and bottom-left, and another in the top-left and bottom-right.
When combined with the orientation of the radio jets, the complicated geometry revealed in the Chandra image may tell the story of what happened to this supermassive black hole and the galaxy it inhabits.
"We think that this black hole has quite a history," said Christopher Reynolds of the University of Maryland in College Park. "Not once, but twice, something has caused this black hole to change its spin axis."
According to the scenario presented by Hodges-Kluck and his colleagues, the spin axis of the black hole ran along a diagonal line from top-right to bottom-left. After a collision with a smaller galaxy, a jet powered by the black hole ignited, blowing away gas to form cavities in the hot gas to the top-right and bottom-left. Since the gas falling onto the black hole was not aligned with the spin of the black hole, the spin axis of the black hole rapidly changed direction, and the jets then pointed in a roughly top-left to bottom-right direction, creating cavities in the hot gas and radio emission in this direction.
Then, either a merging of the two central black holes from the colliding galaxies, or more gas falling onto the black hole caused the spin axis to jerk around to its present direction in roughly a left to right direction. These types of changes in the angle of the spin of a supermassive black hole have previously been suggested to explain X-shaped radio galaxies, but no convincing case has been made in any individual case.
"If we're right, our work shows that jets and cavities are like cosmic fossils that help trace the merger history of an active supermassive black hole and the galaxy it lives in," said Hodges-Kluck. "If even a fraction of X-shaped radio galaxies are produced by such "spin-flips," then their frequency may be important for estimating the detection rates with gravitational radiation missions."
These results appeared in a recent issue of The Astrophysical Journal Letters.
Publicado por Nathaniel en 9:14 No hay comentarios:
Evidence of Water in Lunar Rocks: Water on Moon May Be Widespread, Similar to Earth's
That dry, dusty moon overhead? Seems it isn't quite as dry as it's long been thought to be. Although you won't find oceans, lakes, or even a shallow puddle on its surface, a team of geologists at the California Institute of Technology (Caltech), working with colleagues at the University of Tennessee, has found structurally bound hydroxyl groups (i.e., water) in a mineral in a lunar rock returned to Earth by the Apollo program.
Their findings are detailed in the journal Nature.
"The moon, which has generally been thought to be devoid of hydrous materials, has water," says John Eiler, the Robert P. Sharp Professor of Geology and professor of geochemistry at Caltech, and a coauthor on the paper.
"The fact that we were able to quantitatively measure significant amounts of water in a lunar mineral is truly surprising," adds lead author Jeremy Boyce, a visitor in geochemistry at Caltech, and a research scientist at the University of California, Los Angeles.
The team found the water in a calcium phosphate mineral, apatite, within a basalt collected from the moon's surface by the Apollo 14 astronauts.
To be precise, they didn't find "water" -- the molecule H2O. Rather, they found hydrogen in the form of a hydroxyl anion, OH-, bound in the apatite mineral lattice.
"Hydroxide is a close chemical relative of water," explains coauthor George Rossman, Caltech's Eleanor and John R. McMillan Professor of Mineralogy. "If you heat up the apatite, the hydroxyl ions will 'decompose' and come out as water."
The lunar basalt sample in which the hydrogen was found had been collected by the Apollo 14 moon mission in 1971; the idea to focus the search for water on this particular sample was promoted by Larry Taylor, a professor at the University of Tennessee in Knoxville, who sent the samples to the Caltech scientists last year.
"The moon has been considered to be bone dry ever since the return of the first Apollo rocks," Taylor notes. However, there are lunar volcanic deposits interpreted as having been erupted by expanding vapor. Although carbon dioxide and sulfur gases have generally been thought to dominate the expanding vapor, recent evidence from the study of the these deposits has suggested that water could also play a role in powering lunar volcanic eruptions. The discovery of hydroxyl in apatite from lunar volcanic rocks is consistent with this suggestion.
The idea of looking for water in lunar apatite isn't new, Boyce notes. "Charles B. Sclar and Jon F. Bauer, geoscientists at Lehigh University, first noted that something was missing from the results of chemical analyses of apatite in 1975," he says. "Now, 35 years later, we have quantitative measurements -- and it turns out, they were right. The missing piece was OH."
The Caltech team analyzed the lunar apatite for hydrogen, sulfur, and chlorine using an ion microprobe, which is capable of analyzing mineral grains with sizes much smaller than the width of a human hair. This instrument fires a focused beam of high-energy ions at the sample surface, sputtering away target atoms that are collected and then analyzed in a mass spectrometer. Ion microprobe measurements demonstrated that in terms of its hydrogen, sulfur, and chlorine contents, the lunar apatite in this sample is indistinguishable from apatites from terrestrial volcanic rocks.
"We realized that the moon and the earth were able to make the same kind of apatite, relatively rich in hydrogen, sulfur and chlorine," Boyce says.
Does that mean the moon is as awash in water as our planet? Almost certainly not, say the scientists. In fact, the amount of water the moon must contain to be capable of generating hydroxyl-rich apatite remains an open question. After all, it's hard to scale up the amount of water found in the apatite -- 1600 parts per million or 0.16 percent by weight -- to determine just how much water there is on the lunar landscape. The apatite that was studied is not abundant, and is formed by processes that tend to concentrate hydrogen to much higher levels than are present in its host rocks or the moon as a whole.
"There's more water on the moon than people suspected," says Eiler, "but there's still likely orders of magnitude less than there is on the earth."
Nonetheless, the finding is significant for what it implies about our moon's composition and its history. "These findings tell us that the geological processes on the moon are capable of creating at least one hydrous mineral," Eiler says. "Recent spectroscopic observations of the moon showed that hydrogen is present on its surface, maybe even as water ice. But that could be a thin veneer, possibly hydrogen brought to the moon's surface by comets or solar wind. Our findings show that hydrogen is also part of the rock record of the moon, and has been since early in its history."
Beyond that, Eiler continues, "it's all a great big question mark. We don't know whether these were igneous processes," -- in which rocks are formed by solidification of molten lava -- "or metamorphic" -- in which minerals re-crystallize or change in change in chemistry without melting. "They're both on the table as possible players."
In addition to Boyce, Eiler, Rossman, and Taylor, other authors on the Nature paper, "Lunar apatite with terrestrial volatile abundances," include Research Assistant Professor Yang Liu from the University of Tennessee in Knoxville; Edward Stolper, Caltech's William E. Leonhard Professor of Geology, and Yunbin Guan, manager of Caltech's ion microprobe laboratory.
Their work was funded by grants from NASA's Cosmochemistry Program, the National Science Foundation, and the Gordon and Betty Moore Foundation.
Publicado por Nathaniel en 9:13 No hay comentarios:
martes, 20 de julio de 2010
"Extinct," Pop-Eyed Primate Photographed for First Time
Long thought to be extinct, one of the world's rarest primates has been caught on camera for the first time, scientists announced Monday.
Discovered in 1937 but "missing" for 60 years, Sri Lanka's Horton Plains slender loris was presumed to have died out. In 2002 a fleeting nighttime sighting of something looking like the elusive tree-dweller, however, gave conservationists hope.
Follow-up surveys led by the Zoological Society of London finally confirmed the lorises are alive—if not exactly well—in 2009, when two individuals were photographed and examined.
Initial estimates after the rediscovery put the total world population at fewer than a hundred, said the society's conservation biologist Craig Turner. And in this case, the world is limited to high cloud forests in the Horton Plains area (map) of central Sri Lanka—the animal's only known habitat.
"Potentially this is the rarest primate we're aware of today," Turner said.
About 8 inches (20 centimeters) long and weighing just 11 ounces (310 grams), the slow-moving loris has been doomed as forests have been felled for firewood and to make way for tea plantations and other farms, Turner said.
"There's no means for these lorises to move between the [remaining] forest patches," Turner said. "In terms of breeding and finding mates, it is very difficult for them." (See a satellite picture of Horton Plains' forests.)
"The real focus now has to be on the remaining forest areas and looking at how we can enhance and protect them, and also reconnect them to one another," he added.
"New" Loris Also New Species?
The Horton Plains slender loris is generally classified as a subspecies of Sri Lanka's red slender loris. But, thanks in part to the first ever pictures, researchers now believe the "extinct" loris could be a whole new species.
"It's clearly very different physically," Turner said. Compared to lowland lorises, the Horton Plains loris is "stockier, shorter limbed—and it's got a much longer fur coat."
Ongoing tests on DNA samples taken from the few individuals recorded to date, he added, should help to settle the issue.
Publicado por Nathaniel en 7:49 No hay comentarios:
Surprising Creatures Found Deep off Australia Main Content * A picture of a six-gill shark attacking bait off Australia's Coral Sea, part of a se
Sixgill Shark Attack
Photograph courtesy Queensland Brain Institute
Taking the scientists' bait, a sixgill shark's attack 4,600 feet (1,400 meters) below the surface of the Coral Sea off Australia (see map) is captured in a new video image.
Reaching roughly 13 feet (4 meters) long, the sixgill shark is among deep-sea species never before filmed at such depths, according to the the Queensland Brain Institute, which released the first images from new high-tech remote-control cameras this week.
Often referred to as prehistoric or a "living fossil" because of its resemblance to sharks that lived hundreds of millions of years ago, sixgills are being studied as part of the Deep Australia Project, an ongoing effort to discover the the evolutionary origins of human sight—making the sixgill's night vision of particular interest to researchers.
"This technology will help the discovery of deep-sea creatures' adaptations to the challenges of living at crushing depths and in freezing and dark water," project manager Kylie Greig said in a statement.
"Here they must find food and mates in the dark and avoid being eaten themselves. We are interested in the sensory systems used for this lifestyle."
—With reporting by Dave Hansford in Wellington, New Zealand
Photograph courtesy Queensland Brain Institute
A deep-sea amphipod—a type of crustacean—stares down a remote-control camera in the Coral Sea in a 2006 Deep Australia Project picture.
Living more than 1 mile (1.6 kilometers) below the surface, such creatures must build shells to withstand pressures 140 times greater than those on land, experts say.
Photograph courtesy Queensland Brain Institute
A hairy anglerfish was snapped by remote cameras in 2006 as part of the Deep Australia Project.
The long hairs of the anglerfish—which carry sensory information to the fish's brain—could help neuroscientists better understand human physiology, said project researcher Andy Dunstan.
Photograph courtesy Queensland Brain Institute
These unidentified, bug-eyed oceanic crustaceans, photographed in 2006, are reminders reminder that humans are not the "pinnacle of evolution," said Deep Australia Project leader Justin Marshall.
"In sensory terms, [that's] far from true," Marshall said.
"By taking an approach to sensory systems based [on] ecology, but [which] also includes physiology, anatomy, behavior, and neural integration, we hope to decode signals and their intention in the animal kingdom."
Publicado por Nathaniel en 7:42 No hay comentarios:
Bright Stars of the Brain Regulate Breathing
Astrocytes -- brain cells named after their characteristic star-shape and previously thought to act only as the 'glue' between neurons, have a central role in the regulation of breathing, according to scientists.
The finding provides a new dimension for research into fundamental principles of brain organization and function and may be relevant for understanding causes of devastating conditions associated with respiratory failure such as Sudden Infant Death Syndrome.
The research, funded by the Wellcome Trust and published in Science Express, was carried out by scientists at UCL and the University of Bristol. They demonstrate that brain astrocytes are able to sense the levels of carbon dioxide in the blood. They then activate brain neuronal respiratory networks to increase our breathing in accord with prevailing metabolism and activity.
Astrocytes are a subtype of a group of brain cells known as glia (which means 'glue' in Greek). Glial cells are the most abundant cells in the human brain -- outnumbering neurons by a factor of ten to one. Until very recently, glial cells have been thought to be the less exciting sisters of neurones, merely providing them with structural and nutritional support.
Now, astrocytes have been found to have a unique ability to "taste" the composition of arterial blood entering the brain by sensing increases in arterial levels of carbon dioxide. When activated they release a chemical messenger called ATP which stimulates brain respiratory centres to increase our breathing in order for extra carbon dioxide to be removed from the blood and exhaled.
This observation places astrocytes at the centre of a fundamental regulatory reflex which subconsciously continually adjusts our breathing according to ever changing metabolic and behavioural needs.
Dr Alexander Gourine, a Wellcome Trust Senior Research Fellow in the UCL Department of Neuroscience, Physiology and Pharmacology, who led the study, said: "This research identifies brain astrocytes as previously unrecognized crucial elements of the brain circuits controlling fundamental bodily functions vital for life, such as breathing, and indicates that they are indeed the real stars of the brain.
"This basic science information has to be used rapidly in order to determine whether glial dysfunction contributes to serious disorders of central control of breathing underlying Sudden Infant Death Syndrome and/or congenital central hypoventilation syndrome (Ondine's curse). If this hypothesis is correct astrocytes may be considered as potential targets for therapy in preventing respiratory failure."
The research was carried out in rats using revolutionary gene transfer techniques that allow scientists to observe and control the activity of astrocytes in living brains using light.
Publicado por Nathaniel en 7:40 No hay comentarios:
Suscribirse a: Entradas (Atom)