quinta-feira, 30 de maio de 2013
Meteorite impacts thousands of years ago may have helped to inspire ancient religion.
The 5,000-year-old iron bead might not look like much, but it hides a spectacular past: researchers have found that an ancient Egyptian trinket is made from a meteorite.
The result, published on 20 May in Meteoritics & Planetary Science1, explains how ancient Egyptians obtained iron millennia before the earliest evidence of iron smelting in the region, solving an enduring mystery. It also hints that they regarded meteorites highly as they began to develop their religion.
“The sky was very important to the ancient Egyptians,” says Joyce Tyldesley, an Egyptologist at the University of Manchester, UK, and a co-author of the paper. “Something that falls from the sky is going to be considered as a gift from the gods.”
The tube-shaped bead is one of nine found in 1911 in a cemetery at Gerzeh, around 70 kilometres south of Cairo. The cache dates from about 3,300 bc, making the beads the oldest known iron artefacts from Egypt.
A study in 1928 found that the iron in the beads had a high nickel content — a signature of iron meteorites — and led to the suggestion that it was of celestial origin2. But scholars argued in the 1980s that accidental early smelting could have led to nickel-enriched iron3, and a more recent analysis of oxidized material on the surface of the beads showed low nickel content4.
To settle the argument, Diane Johnson, a meteorite scientist at the Open University in Milton Keynes, UK, and her colleagues used scanning electron microscopy and computed tomography to analyse one of the beads, which they borrowed from the Manchester Museum.
The researchers were not able to cut the precious artefact open, but they found areas where the weathered surface had fallen away, providing what Johnson describes as "little windows" to the preserved metal beneath.
Microscopy showed that the nickel content of this original metal was high — as much as 30% — suggesting that it did indeed come from a meteorite. Backing up this result, the team observed that the metal had a distinctive crystalline structure called a Widmanstätten pattern. This structure is found only in iron meteorites that cooled extremely slowly inside their parent asteroids as the Solar System was forming.
Using tomography, the researchers built up a three-dimensional model of the bead's internal structure, revealing that the ancient Egyptians had made it by hammering a fragment of iron from the meteorite into a thin plate, then bending it into a tube.
Gifts from the gods
The first evidence for iron smelting in ancient Egypt appears in the archaeological record in the sixth century bc. Only a handful of iron artefacts have been discovered in the region from before then: all come from high-status graves such as that of the pharaoh Tutankhamun. "Iron was very strongly associated with royalty and power," says Johnson.
Objects made of such divine material were believed to guarantee their deceased owner priority passage into the afterlife.
Campbell Price, a curator of Egypt and Sudan at the Manchester Museum who was not a member of the study team, emphasizes that nothing is known for certain about the Egyptians’ religious beliefs before the advent of writing. But he points out that later on, during the time of the pharaohs, the gods were believed to have bones made of iron.
He speculates that meteorites may have inspired this belief, the celestial rocks being interpreted as the physical remains of gods falling to Earth.
Johnson says that she would love to check whether other early Egyptian iron artefacts are of meteoritic origin — if she can get permission to study them.
Publicado por Jorge M. Gonçalves às 9:15 da tarde
terça-feira, 28 de maio de 2013
A 16-member research team from the United States, Britain and Belgium has challenged the hotly disputed theory that a massive comet or meteorite struck a glacier-encased Hudson Bay about 13,000 years ago.
The theory suggested that the impact was so strong that it wiped out the mammoths and other Ice Age megafauna. Moreover, it destroyed the first major wave of human migration in the new world.
The research team published their major study in February and said that there us a lack of clear evidence to prove that a four-kilometer-wide comet exploded across the Laurentide Ice Sheet that covered ancient Canada.
"No impact craters of the appropriate size and age are known and no unambiguously shocked material or other features diagnostic of impact have been found to prove the theory", the authors stated in monograph published by the American Geophysical Union
They said that the proponents are trying to explain the climatological, paleontological and archeological events that are not unique and do not require and impact. For example, layers of so-called shocked rocks and minerals are suggested by the theory to have transformed by an earth-shaking mega-blast.
However, a team of 29 scientists from the U. S., Mexico, the Netherlands, Germany and the Czech Republic contradicted the February findings in a new, pro-impact study published online in the Proceedings of the National Academy of Sciences.
Publicado por Jorge M. Gonçalves às 5:30 da tarde
quarta-feira, 22 de maio de 2013
The Martian meteorite NWA 7397 was found in 2012 in Morocco's Sahara Desert. Scientists think it was part of a chunk of Mars that was chipped from the planet when an asteroid impacted it. At 1.37 lbs (0.62 kg), the sample going up for sale is the larger portion of themeteorite that landed on Earth; the rest of that rock was recently bought by a museum, according to Heritage Auctions, which is handling the sale.
Meteorites that came from Mars are incredibly rare — less than 300 pounds of them in total are known to exist on Earth. They tend to fetch higher prices than other types of meteorites, which usually originate from outer space, and sometimes the moon. The largest lunar meteorite ever auctioned, the4-lb (1.8 kg) Dar al Gani 1058 specimen, sold for $330,000 in an October 2012 Heritage Auction sale.
The NWA 7397 meteorite is going on sale as part of a large collection of meteorites, fossils, and insects preserved in amber.
"The specimens in this sale represent some of the finest fossils, meteorites, and natural history items I have had the privilege to handle," Craig Kissick, associate director of nature and science for Heritage Auctions, said in a statement. "This auction will appeal to everyone fascinated by natural history and truly has something for everyone — even those new to this collecting genre."
Some other meteorites on sale in the collection are also expected to fetch high prices. Another meteorite found in the Sahara Desert of Morocco, classified as a chondrite meteorite, should sell for at least $15,000, experts say. At 19.57 lbs (8.9 kg), that specimen is much larger than the Martian meteorite, and features the largest example of gem-like olivine crystals ever collected, embedded in a silver nickel-ore matrix. A third space rock, a 16.86-lb (7.6 kg) muonionalusta iron meteorite, has been carved and polished into a "modern work of art," according to Heritage Auctions, and should bring in at least $18,000.
Other prizes going up at auction include a tuft of wooly mammoth wool 16 inches long (41 cm) that dates from the Pleistocene epoch (expected to sell for $400), and a prehistoric specimen of amber (fossilized tree sap) that caught two tiny midges in the act of copulation (estimated at $300).
Publicado por Jorge M. Gonçalves às 6:39 da tarde
sexta-feira, 10 de maio de 2013
A small meteorite landed on a house in Waterbury, Connecticut on Wednesday.
Experts from the Yale Peabody Museum of Natural History say the meteorite crashed through the gutter and landed on the lawn below. It was about the size and shape of an avocado and weighs 1.6 pounds.
The homeowner contacted Dr. Stefan Nicolescu, mineralogy collections manager at the Peabody Museum, who had also confirmed the identity of the Wolcott meteorite from last month.
"It's not very often that this happens, that in one meteorite shower two or more buildings are hit at the same time," Dr. Nicolescu told WTNH (http://bit.ly/13mfpMX). "These are rather rare occurrences so that's what actually makes this event so much more interesting than a regular meteorite find or a regular meteorite fall." All but one of the reported meteorite falls in Connecticut have occurred in towns beginning with the letter "W," Weston and Wethersfield.
Last month, a baseball-sized meteorite crashed into a Wolcott house damaging a roof and the attic. Area police reported that several residents reported hearing loud booms that night.
The town of Wethersfield makes Connecticut history by having two meteorites hit two separate homes between 1971 - 1982. Remarkably in both cases, the homes were occupied when the meteorites came crashing through the ceilings and no one was injured.
One of the most notable metrorites fell on Dec. 14, 1807. Although it is called the "Weston meteorite," most of it fell in what is now Easton, which was founded in 1845 from 28.8 square miles carved out of Weston. Today it's believed that none or almost none of the pieces fell in present-day Weston, although pieces were found in a swath that extended from Monroe to Fairfield.
The object was sufficiently bright to illuminate fields and barns, and there were reports of something strange streaking across the sky from as far away as Rutland, Vt. The meteor broke up as it slammed into the earth's atmosphere at about 65,000 mph. Soon it seemed that Weston was a target of an artillery barrage, as dozens of rocks, one weighing 200 pounds, augered into the snow-covered fields.
According to a book by Cathryn J. Prince, of Weston, "A Professor, a President, and a Meteor: The Birth of American Science," the meteorite provided the spark that over time turned the new nation, then populated largely by people who believed in the supernatural, into a scientific powerhouse.
WTNH, News Channel 8, contributed to this story.
Publicado por Jorge M. Gonçalves às 10:38 da tarde
quarta-feira, 8 de maio de 2013
Earth is bombarded all the time by space rocks, but people rarely notice them--only 1,042 have ever been seen falling. People didn’t start recording these impacts until a couple hundred years ago, and then suddenly, they noticed all the time.
Data designer Carlo Zapponi has a lovely new animation, Bolides, showing all these recorded impacts, along with every known meteorite fall--most of which weren’t seen when they happened. The information comes from The Meteorite Bulletin, which is maintained by the Nomenclature Committee of the Meteoritical Society. The word "bolide" comes from the Greek word for missile, and is used to describe bright fireballs.
The database doesn't yet include the giant Chelyabinsk meteorite, which fell over Russia earlier this year. But it's still fun to explore meteorite falls by size and watch Earth get bombarded through time. Go here to see the animation for yourself.: http://bolid.es/
Publicado por Jorge M. Gonçalves às 10:25 da tarde