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Offline Orionid

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« Odpowiedź #30 dnia: Sierpień 22, 2018, 00:03 »
Najstarsze skały na Ziemi powstały pod wpływem upadków meteorytów
18.08.2018

Wyniki najnowszych badań przedstawionych w „Nature Geoscience” sugerują, że najstarsze wyewoluowane znane skały na naszej planecie najprawdopodobniej powstały na skutek bombardowania powierzchni przez planetoidy (asteroidy) lub meteoryty.

Najstarsze wyewoluowane skały granitowe na Ziemi, to liczące sobie 4,02 miliarda lat gnejsy z kompleksu gnejsów rzeki Acasta w północno-zachodniej Kanadzie, nazwane Idiwhaa, od terminu z języka ludu Tlicho (nazwa wywodzi się od określenia „starożytny” w języku tego ludu). Jednak skład tych skał różni się od typowej dawnej skorupy kontynentalnej. Różnice te oznaczają, że uformowały się w innym procesie.

Naukowcy z grupy, którą kierował dr Tim Johnson z Curtin University w Perth (Australia), użyli modelowania komputerowego, aby pokazać, że skały te wytworzyły się przez częściowe stopienie bogatych w żelazo, uwodnionych skał bazaltowych, w bardzo niskim ciśnieniu, odpowiadającym warunkom panującym w najwyższych kilku kilometrach skorupy ziemskiej.

Jak mówi dr Johnson, najłatwiej wytłumaczyć to przez upadki meteorytów, które dostarczyły energii potrzebnej do uzyskania wysokiej temperatury potrzebnej do stopienia skał. Symulacje komputerowe pokazały, że taki scenariusz jest fizycznie możliwy, a na dodatek musiało to być dość powszechne.

„Biorąc pod uwagę sporą ilość meteorytów około cztery miliardy lat temu, topnienie pod wpływem ich upadków mogło być dominującym mechanizmem tworzącym w tamtych czasach skały granitowe” - tłumaczy Johnson.

Naukowcy szacują, że stopieniu ulegały skały do 3 km w głąb górnej warstwy skorupy ziemskiej. Być może zbadane skały są jedynymi, które przetrwały do dzisiejszych czasów z tamtej epoki. Przypuszcza się, że w hadeiku i najwcześniejszych erach archaiku, czyli od około 4,5 miliarda do około 3,9 miliarda lat temu, miało miejsce intensywne bombardowanie Ziemi przez planetoidy (asteroidy), co powodowało topienie i przetwarzanie skał na powierzchni na skalę globalną.

Więcej na ten temat: https://www.nature.com/articles/s41561-018-0206-5.epdf?author_access_token=VidksO1cJab8OVR1mD1QZNRgN0jAjWel9jnR3ZoTv0OBIj2PN8NXu7ShpxQJdVbaejg7_EV13iMXwN_M4S8bv8ffRaiFW-bCrToH7YkG9JKLN2lalVdV5SDrE0j5vFNHcGSvKw-gxQsxlKlwNO28OA%3D%3D

(PAP)
http://naukawpolsce.pap.pl/aktualnosci/news%2C30649%2Cnajstarsze-skaly-na-ziemi-powstaly-pod-wplywem-upadkow-meteorytow.html

Meteorite bombardment likely to have created the Earth's oldest rocks
Date: August 14, 2018
Source: Goldschmidt Conference

(...)  Scientists have found that 4.02-billion-year-old silica-rich felsic rocks from the Acasta River, Canada -- the oldest rock formation known on Earth -- probably formed at high temperatures and at a surprisingly shallow depth of the planet's nascent crust. The high temperatures needed to melt the shallow crust were likely caused by a meteorite bombardment around half a billion years after the planet formed. This melted the iron-rich crust and formed the granites we see today. These results are presented for the first time at the Goldschmidt conference in Boston (14 August), following publication in the peer-reviewed journal Nature Geoscience. (...)

We estimate that rocks within the uppermost 3km of mafic crust would have been melted in producing the rocks we see today. We think that these ancient felsic rocks would have been very common, but the passage of 4 billion years, and the development of plate tectonics, means that almost nothing remains. (...)
https://www.sciencedaily.com/releases/2018/08/180813113334.htm

Offline Orionid

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« Odpowiedź #31 dnia: Sierpień 24, 2018, 02:50 »
Chondryt węglowy Y-793261 znaleziony na Antarktydzie w 1979 może swym składem być podobny do 162173 Ryugu .
Przebadany meteoryt charakteryzuje się cechami wskazującymi na  kondensację krzemionki w dysku protoplanetarnym.

Summary: Scientists discovered silica mineral quartz in a primitive meteorite, becoming the first in the world to present direct evidence of silica condensation within the solar protoplanetary disk. They also found ultrarefractory scandium- and zirconium-bearing minerals in the meteorite, which implies that the minerals condensed from nebular gas over a wide temperature range.
https://www.sciencedaily.com/releases/2018/08/180822091025.htm

Crystalline silica in meteorite brings scientists closer to understanding solar evolution
August 23, 2018, Waseda University


Image of the solar protoplanetary nebula. The image on the left is the structure of crystalline silica, and on the right is an electron micrograph of the amoeboid olivine aggregate the research team found in the primitive meteorite, Yamato-793261. (©NASA/JPL-Caltech)

A multi-institutional team of researchers has discovered silica mineral quartz in a primitive meteorite, comprising direct evidence of silica condensation within the solar protoplanetary disk, and offering new clues to understanding solar formation and evolution. Though previous infrared spectroscopic observations have suggested the existence of silica in young and newly formed T Tauri stars as well as in asymptotic giant branch (AGB) stars in their last phase of life, no evidence of gas-solid condensation of silica had been found in other primitive meteorites from the early stages of the solar system.

The scientists studied the primitive meteorite Yamato-793261 (Y-793261), a carbonaceous chondrite collected from an ice field near the Yamato Mountains during the 20th Japan Antarctic Research Expedition in 1979.

"The degree of crystallinity of organic matter in Y-793261 shows that it did not undergo thermal metamorphism," explains Timothy Jay Fagan, professor of geochemistry at Waseda University. "This confirms that Y-793261 preserves minerals and textures of its nebular origin, providing us with records of the early solar system."

A major component of chondrites includes refractory inclusions, which form at high temperatures and are the oldest solar system solids dated. Refractory inclusions can be subdivided into calcium-aluminum-rich inclusions (CAIs) and amoeboid olivine aggregates (AOAs). The research team found an AOA in Y-793261 containing typical AOA minerals and ultra-refractory (very high temperature) scandium- and zirconium-bearing minerals, along with the quartz (which forms at comparatively lower temperature). "Such variety in minerals implies that the AOA condensed from nebular gas to solid over a wide temperature range from approximately 1500–900°C," Professor Fagan says.S "This aggregate is the first of its kind to be found in our solar system."


Primitive meteorite Y-793261. Credit: Waseda University

They also found that the quartz in the AOA has an oxygen isotopic composition close to the sun's. This isotopic composition is typical of refractory inclusions in general, which indicates that refractory inclusions formed close to the protosun (approximately 0.1 AU, or 1/10 of the distance from the Earth to the sun). The fact that the quartz in the Y-793261 shares this isotopic composition indicates that the quartz formed in the same setting in the solar nebula. However, silica condensation from solar nebula gas is hypothetically impossible if minerals and gas remain in equilibrium during condensation. This finding serves as evidence that the AOA formed from a rapidly cooling gas. As silica-poor minerals condensed from the gas, the gas changed composition, becoming more silica-rich, until the quartz became stable and crystallized.

Professor Fagan says that the origin of Y-793261 is most likely an astronomical object near 162173 Ryugu (commonly known as Ryugu), an asteroid named after a dragon's palace from an old Japanese folktale. Currently being investigated by the Japanese spacecraft Hayabusa 2, Ryugu may share the same properties as Y-793261 and potentially provide more records on the early solar system. "By combining ongoing research on meteorites with new results from Ryugu, we hope to better understand the thermal events and transfers of mass that occurred during the beginning stages of our solar system."

This study was published online in Proceeding of the National Academy of Sciences of the United States of America (PNAS) on July 2, 2018 (EST).

https://www.waseda.jp/top/en-news/60739

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« Odpowiedź #32 dnia: Wrzesień 05, 2018, 08:06 »
Największy brazylijski meteoryt przetrwał pożar muzeum w Rio de Janeiro, w którym go przechowywano:

fter a catastrophic fire blazed through the National Museum of Brazil on Sunday (Sept. 2), destroying many of the institution's 20 million artifacts, the museum's meteorites were some of the few relics left standing.

Among the space rocks that survived the blaze is the Bendegó meteorite, which is the largest meteorite ever found on Brazilian soil. The iron-nickel meteorite is one of about a dozen meteorites housed at the museum.

Discovered by a cattle farmer near the town of Monte Santo in the Brazilian state of Bahia in 1784, the Bendegó meteorite weighs about 11,600 lbs. (5,260 kilograms). That's more than twice as much as an average car, all packed into a space rock the size of a motorcycle. At the time of the object's discovery, it was the second-largest meteorite ever found


https://www.space.com/41710-bendego-meteorite-survives-brazil-museum-fire.html


Offline Orionid

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« Odpowiedź #33 dnia: Styczeń 25, 2019, 07:47 »
A meteorite hit the moon during Monday’s total lunar eclipse
22 January 2019



(...) Jose Maria Madiedo at the University of Huelva in Spain has confirmed that the impact is genuine. For years, he and his colleagues have been hoping to observe a meteorite impact on the moon during a lunar eclipse, but the brightness of these events can make that very difficult – lunar meteorite impacts have been filmed before, but not during an eclipse. (...)

<a href="http://www.youtube.com/watch?v=FNvfBCu-jjI" target="_blank">http://www.youtube.com/watch?v=FNvfBCu-jjI</a>
https://www.youtube.com/watch?v=FNvfBCu-jjI

https://www.newscientist.com/article/2191526-a-meteorite-hit-the-moon-during-mondays-total-lunar-eclipse/


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« Odpowiedź #34 dnia: Styczeń 28, 2019, 19:00 »
Meteoryt starszy niż Ziemia
BY KRZYSZTOF KANAWKA ON 28 STYCZNIA 2019


Odnaleziony meteoryt / Credits - Curtin University

Meteoryt, który spadł w listopadzie 2015 roku w Australii, okazał się być starszy niż Ziemia.

Dwudziestego siódmego listopada 2015 roku w południowej Australii spadł meteoryt. Zjawisko było obserwowane, w tym przez australijską sieć bolidów, co pozwoliło na wyznaczenie miejsca spadku. Meteoryt udało się zlokalizować pod koniec grudnia. Ten meteoryt, o masie około 1,7 kg, zaledwie kilka dni później mógłby być znacznie trudniejszy do wykrycia, gdyż spodziewane deszcze mogłyby przykryć region spadku grubszą warstwą mułu. W poszukiwaniach brali udział australijscy naukowcy z Curtin University.

Po pierwszych badaniach meteoryt okazał się być chondrytem, czyli kamiennym meteorytem. Dalsza analiza tego meteorytu wykazała, że wiek tego meteorytu to przynajmniej 4,5 miliarda lat. Innymi słowy, jest bardzo prawdopodobne, że ten meteoryt powstał jeszcze zanim Ziemia się uformowała. (...)

https://kosmonauta.net/2019/01/meteoryt-starszy-niz-ziemia/#prettyPhoto
https://www.abc.net.au/news/2016-01-06/ancient-meteorite-found-at-lake-eyre-by-curtin-university-team/7071952

Offline Robek

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« Odpowiedź #35 dnia: Styczeń 28, 2019, 21:10 »
Dwudziestego siódmego listopada 2015 roku w południowej Australii spadł meteoryt. Zjawisko było obserwowane, w tym przez australijską sieć bolidów, co pozwoliło na wyznaczenie miejsca spadku. Meteoryt udało się zlokalizować pod koniec grudnia. Ten meteoryt, o masie około 1,7 kg, zaledwie kilka dni później mógłby być znacznie trudniejszy do wykrycia, gdyż spodziewane deszcze mogłyby przykryć region spadku grubszą warstwą mułu. W poszukiwaniach brali udział australijscy naukowcy z Curtin University.


Tak duży meteoryt, musiał zrobić dość spory krater w ziemi, są jakieś zdjęcia tego krateru?   

Offline Orionid

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« Odpowiedź #36 dnia: Styczeń 28, 2019, 21:59 »
Dwudziestego siódmego listopada 2015 roku w południowej Australii spadł meteoryt. Zjawisko było obserwowane, w tym przez australijską sieć bolidów, co pozwoliło na wyznaczenie miejsca spadku. Meteoryt udało się zlokalizować pod koniec grudnia. Ten meteoryt, o masie około 1,7 kg, zaledwie kilka dni później mógłby być znacznie trudniejszy do wykrycia, gdyż spodziewane deszcze mogłyby przykryć region spadku grubszą warstwą mułu. W poszukiwaniach brali udział australijscy naukowcy z Curtin University.

Tak duży meteoryt, musiał zrobić dość spory krater w ziemi, są jakieś zdjęcia tego krateru?

Zbyt mały , by po wyhamowaniu atmosferycznym było to możliwe.
Cytuj
Observations from the air turned out to be critical as the impact site had deteriorated from rain.

Tutaj o szkodach spowodowanych przez meteoryty większe od tutaj prezentowanego:

Cytuj
Throughout history there have been reports of stones falling from the sky, but the scientific community did not recognize the extraterrestrial origin of meteorites until the 1700s.  Within recent history meteorites have even hit humans-

1938 - a small meteorite crashed through the roof of a garage in Illinois
1954 - A 5kg meteorite fell through the roof of a house in Alabama.
1992 - A small meteorite demolished a car near New York City.
2003 - A 20 kg meteorite crashed through a 2 story house in uptown New Orleans
2003 - A shower of meteorites destroyed several houses and injured 20 people in India
http://www.tulane.edu/~sanelson/Natural_Disasters/impacts.htm

O największych kraterach uderzeniowych na Ziemi:
https://www.livescience.com/45126-biggest-impact-crater-earth-countdown.html

Offline kanarkusmaximus

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« Odpowiedź #37 dnia: Styczeń 29, 2019, 16:05 »
Tak a propos- chyba nie ma żadnej strony czy bazy danych dotyczącej spadków świeżych meteorytów? (Oczywiście tylko tych, które się udało złapać :) ).

Offline Orionid

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« Odpowiedź #38 dnia: Styczeń 30, 2019, 01:15 »
Na tej stronie lista spadków w obecnym stuleciu:

21st Century Meteorite Witnessed Falls

2018

Jan 16, 2018 - Hamburg (H4 chondrite) : Michigan USA
Feb 16, 2018 - Ablaketka (H5 chondrite) : Kazakhstan
Mar 07, 2018 - "Grays Harbor" (unofficial) (unknown type) : Pacific Ocean (Washington coast, USA)
Apr 19, 2018 - Aba Panu (L3-6 chondrite) : Nigeria
Jun 01, 2018 - Mangui (L6 chondrite) : China (Hammer)
Jun 02, 2018 - "Central Kalahari" (unofficial) (unknown type) : Botswana
Jun 21, 2018 - Ozerki (L6 chondrite) : Russia
Jul 10, 2018 - Renchen (L5-6 chondrite) : Germany
Jul 27, 2018 - "Glendale" (unofficial) (ordinary chondrite?) : Arizona USA
July 27, 2018 - "Benenitra" (L6 chondrite) : Madagascar
Aug 12-17?, 2018 - "Bhakkar" (unofficial) (ordinary chondrite?) : Pakistan
Aug 21, 2018 - Gueltat Zemmour (L4 chondrite) : Morocco
Sep 26, 2018 - "Komaki" (unofficial) (ordinary chondrite) : Japan (Hammer)

http://galactic-stone.com/pages/falls

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« Ostatnia zmiana: Styczeń 30, 2019, 01:49 wysłana przez Orionid »

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« Odpowiedź #40 dnia: Luty 11, 2019, 22:06 »
Niespodziewane uderzenie w Kube:
http://en.granma.cu/cuba/2019-02-11/new-revelations-about-vinales-meteorite
Z powazaniem
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JID: adam.przybyla@gmail.com

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« Odpowiedź #41 dnia: Marzec 30, 2019, 21:25 »
Odkryto cmentarzysko ofiar kataklizmu sprzed 66 mln lat.

66 million-year-old deathbed linked to dinosaur-killing meteor
By Robert Sanders, Media relations| MARCH 29, 2019


A meteor impact 66 million years ago generated a tsunami-like wave in an inland sea that killed and buried fish, mammals, insects and a dinosaur, the first victims of Earth’s last mass extinction event. The death scene from within an hour of the impact has been excavated at an unprecedented fossil site in North Dakota. (Graphics and photos courtesy of Robert DePalma)

The beginning of the end started with violent shaking that raised giant waves in the waters of an inland sea in what is now North Dakota.

Then, tiny glass beads began to fall like birdshot from the heavens. The rain of glass was so heavy it may have set fire to much of the vegetation on land. In the water, fish struggled to breathe as the beads clogged their gills.

The heaving sea turned into a 30-foot wall of water when it reached the mouth of a river, tossing hundreds, if not thousands, of fresh-water fish — sturgeon and paddlefish — onto a sand bar and temporarily reversing the flow of the river. Stranded by the receding water, the fish were pelted by glass beads up to 5 millimeters in diameter, some burying themselves inches deep in the mud. The torrent of rocks, like fine sand, and small glass beads continued for another 10 to 20 minutes before a second large wave inundated the shore and covered the fish with gravel, sand and fine sediment, sealing them from the world for 66 million years.

This unique, fossilized graveyard — fish stacked one atop another and mixed in with burned tree trunks, conifer branches, dead mammals, mosasaur bones, insects, the partial carcass of a Triceratops, marine microorganisms called dinoflagellates and snail-like marine cephalopods called ammonites — was unearthed by paleontologist Robert DePalma over the past six years in the Hell Creek Formation, not far from Bowman, North Dakota. The evidence confirms a suspicion that nagged at DePalma in his first digging season during the summer of 2013 — that this was a killing field laid down soon after the asteroid impact that eventually led to the extinction of all ground-dwelling dinosaurs. The impact at the end of the Cretaceous Period, the so-called K-T boundary, exterminated 75 percent of life on Earth.


“This is the first mass death assemblage of large organisms anyone has found associated with the K-T boundary,” said DePalma, curator of paleontology at the Palm Beach Museum of Natural History in Florida and a doctoral student at the University of Kansas. “At no other K-T boundary section on Earth can you find such a collection consisting of a large number of species representing different ages of organisms and different stages of life, all of which died at the same time, on the same day.”


Fossilized fish piled one atop another, suggesting that they were flung ashore and died stranded together on a sand bar after the seiche withdrew.

In a paper to be published next week in the journal Proceedings of the National Academy of Sciences, he and his American and European colleagues, including two University of California, Berkeley, geologists, describe the site, dubbed Tanis, and the evidence connecting it with the asteroid or comet strike off Mexico’s Yucatan Peninsula 66 million years ago. That impact created a huge crater, called Chicxulub, in the ocean floor and sent vaporized rock and cubic miles of asteroid dust into the atmosphere. The cloud eventually enveloped Earth, setting the stage for Earth’s last mass extinction.

“It’s like a museum of the end of the Cretaceous in a layer a meter-and-a-half thick,” said Mark Richards, a UC Berkeley professor emeritus of earth and planetary science who is now provost and professor of earth and space sciences at the University of Washington.

Richards and Walter Alvarez, a UC Berkeley Professor of the Graduate School who 40 years ago first hypothesized that a comet or asteroid impact caused the mass extinction, were called in by DePalma and Dutch scientist Jan Smit to consult on the rain of glass beads and the tsunami-like waves that buried and preserved the fish. The beads, called tektites, formed in the atmosphere from rock melted by the impact.

Tsunami vs. seiche

Richards and Alvarez determined that the fish could not have been stranded and then buried by a typical tsunami, a single wave that would have reached this previously unknown arm of the Western Interior Seaway no less than 10 to 12 hours after the impact 3,000 kilometers away, if it didn’t peter out before then. Their reasoning: The tektites would have rained down within 45 minutes to an hour of the impact, unable to create mudholes if the seabed had not already been exposed.


Walter Alvarez and Robert DePalma at the Tanis outcrop in North Dakota.

Instead, they argue, seismic waves likely arrived within 10 minutes of the impact from what would have been the equivalent of a magnitude 10 or 11 earthquake, creating a seiche (pronounced saysh), a standing wave, in the inland sea that is similar to water sloshing in a bathtub during an earthquake. Though large earthquakes often generate seiches in enclosed bodies of water, they’re seldom noticed, Richards said. The 2011 Tohoku quake in Japan, a magnitude 9.0, created six-foot-high seiches 30 minutes later in a Norwegian fjord 8,000 kilometers away.

“The seismic waves start arising within nine to 10 minutes of the impact, so they had a chance to get the water sloshing before all the spherules (small spheres) had fallen out of the sky,” Richards said. “These spherules coming in cratered the surface, making funnels — you can see the deformed layers in what used to be soft mud — and then rubble covered the spherules. No one has seen these funnels before.”

The tektites would have come in on a ballistic trajectory from space, reaching terminal velocities of between 100 and 200 miles per hour, according to Alvarez, who estimated their travel time decades ago.

“You can imagine standing there being pelted by these glass spherules. They could have killed you,” Richards said. Many believe that the rain of debris was so intense that the energy ignited wildfires over the entire American continent, if not around the world.


Tektites, 1 millimeter spheres of glass, recovered from the Tanis fossil bed.

“Tsunamis from the Chicxulub impact are certainly well-documented, but no one knew how far something like that would go into an inland sea,” DePalma said. “When Mark came aboard, he discovered a remarkable artifact — that the incoming seismic waves from the impact site would have arrived at just about the same time as the atmospheric travel time of the ejecta. That was our big breakthrough.”

At least two huge seiches inundated the land, perhaps 20 minutes apart, leaving six feet of deposits covering the fossils. Overlaying this is a layer of clay rich in iridium, a metal rare on Earth, but common in asteroids and comets. This layer is known as the K-T, or K-Pg boundary, marking the end of the Cretaceous Period and the beginning of the Tertiary Period, or Paleogene.

Iridium

In 1979, Alvarez and his father, Nobelist Luis Alvarez of UC Berkeley, were the first to recognize the significance of iridium that is found in 66 million-year-old rock layers around the world. They proposed that a comet or asteroid impact was responsible for both the iridium at the K-T boundary and the mass extinction.


Jan Smit, Mark Richards and Walter Alvarez at the North Dakota site of dinosaur-killing meteor’s first victims.

The impact would have melted the bedrock under the seafloor and pulverized the asteroid, sending dust and melted rock into the stratosphere, where winds would have carried them around the planet and blotted out the sun for months, if not years. Debris wold have rained down from the sky: not only tektites, but also rock debris from the continental crust, including shocked quartz, whose crystal structure was deformed by the impact.

The iridium-rich dust from the pulverized meteor would have been the last to fall out of the atmosphere after the impact, capping off the Cretaceous.

“When we proposed the impact hypothesis to explain the great extinction, it was based just on finding an anomalous concentration of iridium — the fingerprint of an asteroid or comet,” said Alvarez. “Since then, the evidence has gradually built up. But it never crossed my mind that we would find a deathbed like this.”

Key confirmation of the meteor hypothesis was the discovery of a buried impact crater, Chicxulub, in the Caribbean and off the coast of the Yucatan in Mexico, that was dated to exactly the age of the extinction. Shocked quartz and glass spherules were also found in K-Pg layers worldwide. The new discovery at Tanis is the first time the debris produced in the impact was found along with animals killed in the immediate aftermath of the impact.

<a href="http://www.youtube.com/watch?v=EpNMHwnxpC8" target="_blank">http://www.youtube.com/watch?v=EpNMHwnxpC8</a>
https://www.youtube.com/watch?v=EpNMHwnxpC8&feature=youtu.be

Robert DePalma excavating at the Tanis fossil site in North Dakota.

“And now we have this magnificent and completely unexpected site that Robert DePalma is excavating in North Dakota, which is so rich in detailed information about what happened as a result of the impact,” Alvarez said. “For me, it is very exciting and gratifying!”

Tektites

Jan Smit, a retired professor of sedimentary geology from Vrije Universiteit in Amsterdam in The Netherlands who is considered the world expert on tektites from the impact, joined DePalma to analyze and date the tektites from the Tanis site. Many were found in near perfect condition embedded in amber, which at the time was pliable pine pitch.


Fish carcasses and two logs tossed together by the seiche created by seismic waves from the meteor impact.

“I went to the site in 2015 and, in front of my eyes, he (DePalma) uncovered a charred log or tree trunk about four meters long which was covered in amber, which acted as sort of an aerogel and caught the tektites when they were coming down,” Smit said. “It was a major discovery, because the resin, the amber, covered the tektites completely, and they are the most unaltered tektites I have seen so far, not 1 percent of alteration. We dated them, and they came out to be exactly from the K-T boundary.”

The tektites in the fishes’ gills are also a first.

“Paddlefish swim through the water with their mouths open, gaping, and in this net, they catch tiny particles, food particles, in their gill rakers, and then they swallow, like a whale shark or a baleen whale,” Smit said. “They also caught tektites. That by itself is an amazing fact. That means that the first direct victims of the impact are these accumulations of fishes.”

Smit also noted that the buried body of a Triceratops and a duck-billed hadrosaur proves beyond a doubt that dinosaurs were still alive at the time of the impact.

“We have an amazing array of discoveries which will prove in the future to be even more valuable,” Smit said. “We have fantastic deposits that need to be studied from all different viewpoints. And I think we can unravel the sequence of incoming ejecta from the Chicxulub impact in great detail, which we would never have been able to do with all the other deposits around the Gulf of Mexico.”


A perfectly preserved fish tail from Tanis deposit.

“So far, we have gone 40 years before something like this turned up that may very well be unique,” Smit said. “So, we have to be very careful with that place, how we dig it up and learn from it. This is a great gift at the end of my career. Walter sees it as the same.”

Co-authors with DePalma, Smit, Richards and Alvarez are David Burnham of the University of Kansas, Klaudia Kuiper of Vrije Universiteit, Phillip Manning of Manchester University in the United Kingdom, Anton Oleinik of Florida Atlantic University, Peter Larson of the Black Hills Institute of Geological Research in South Dakota, Florentin Maurrasse of Florida International University, Johan Vellekoop of Katholieke Universiteit Leuven in Belgium and Loren Gurche of the Palm Beach Museum of Natural History.
https://news.berkeley.edu/2019/03/29/66-million-year-old-deathbed-linked-to-dinosaur-killing-meteor/

Zwęglone kości dinozaurów świadectwem zagłady sprzed 66 mln lat
06.04.2019

Zwęglone kości dinozaurów i innych zwierząt są świadectwem wymierania wywołanego uderzeniem w Ziemię planetoidy 66 mln lat temu. Zwierzęta, których szczątki odnaleziono, mogły zginąć kilka chwil po uderzeniu – informują naukowcy na łamach pisma „PNAS”.

Na stanowisku paleontologicznym w Dakocie Północnej (USA) odkryto szczątki roślin i zwierząt, w tym dinozaurów, ssaków, ryb i owadów, zwęglone w wyniku uderzenia w Ziemię planetoidy, która 66 mln lat temu wywołała wielkie wymieranie.

Uderzyła ona w półwysep Jukatan, a pozostałością jest krater Chicxulub. W wyniku kosmicznej kolizji i jej następstw doszło do wyginięcia 75 proc. organizmów ziemskich.

Zdaniem naukowców jest to najbogatsze stanowisko paleontologiczne z przełomu kredy i trzeciorzędu.

Skamieniałości ryb znajdują się jedna nad drugą, co może oznaczać, że ryby wyrzuciła na brzeg wysoka, nagła fala, która podniosła się wskutek trzęsienia ziemi. Po tym nastąpił intensywny deszcz gorącego, drobnego szkliwa wulkanicznego. Mógł on spowodować pożary roślin na ogromnych obszarach. Następna wysoka fala przyniosła piach i żużel, które grubą warstwą przykryły wyrzucone na brzeg ryby.

Obok znajdują się zwęglone pnie drzew, szczątki ssaków, mozazaura, owady, fragmenty ciała triceratopsa oraz drobne zwierzęta morskie.

Stanowisko odkrył w 2013 r. paleontolog Robert DePalma, od tego czasu prowadzone są na nim prace badawcze. W najnowszym artykule naukowcy z międzynarodowego zespołu dowodzą, że istniało bezpośrednie powiązanie między stanowiskiem w Dakocie Północnej a uderzeniem w półwysep Jukatan.

Naukowcy z międzynarodowego zespołu badali m.in. wulkaniczne drobne szkliwo, zwane tektytami, które spadało do wody. Część tego szkliwa zachowała się m.in. w bursztynie, kiedy wpadła do kropli żywicznych na drzewach. Inne ziarna szkliwa wpadły do wody. Naukowcy zaobserwowali, że jednymi z pierwszych ofiar tego gorącego deszczu były ryby, takie jak jesiotry, które nałykały się tektytów w wodzie.

Więcej: https://news.berkeley.edu/2019/03/29/66-million-year-old-deathbed-linked-to-dinosaur-killing-meteor/ (PAP)
http://naukawpolsce.pap.pl/aktualnosci/news%2C33475%2Czweglone-kosci-dinozaurow-swiadectwem-zaglady-sprzed-66-mln-lat.html
« Ostatnia zmiana: Maj 01, 2019, 08:43 wysłana przez Orionid »

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Odp: Meteory, meteoryty, bolidy
« Odpowiedź #42 dnia: Marzec 30, 2019, 21:35 »
Niesamowite odkrycie! To jak zapis filmu z przebiegu katastrofy!  To nie martwy krater na Jukatanie ale jakby żywy i dynamiczny zapis Dies Irae w skałach!

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Odp: Meteory, meteoryty, bolidy
« Odpowiedź #43 dnia: Marzec 30, 2019, 22:12 »
Akurat  mija 20 lat od ukazania się  po polsku książki, która niczym dobry kryminał przybliża hipotezę tej zagłady.

https://www.biblionetka.pl/book.aspx?id=15059
http://lubimyczytac.pl/ksiazka/60053/dinozaury-i-krater-smierci
https://en.wikipedia.org/wiki/T._Rex_and_the_Crater_of_Doom
« Ostatnia zmiana: Marzec 30, 2019, 22:15 wysłana przez Orionid »

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Odp: Meteory, meteoryty, bolidy
« Odpowiedź #44 dnia: Kwiecień 06, 2019, 10:18 »
Witam, dziś o godź 02.05  potężny bolid się pojawił. Na północnym niebie, tak z Wielkiej Niedzwiedzicy na cefeusza leciał. Zielone światło było tak intensywne , że oświetliło okolice. Rozpadł się na dwa mniejsze kawałki i  na koniec  był niezły rozbłysk. A mój cień poruszający się i to światło rozbiło mnie na atomy :)
Miał ktoś przyjemność jeszcze to zjawisko zaobserwować?