“Sikhote-Alin meteorite”的意思、由来-开放百科全书

An iron meteorite fell on the Sikhote-Alin Mountains, in southeastern Russia, in 1947. Though large iron meteorite falls had been witnessed previously and fragments recovered, never before in recorded history had a fall of this magnitude been observed.^[2] An estimated 23 tonnes^[1] of fragments survived the fiery passage through the atmosphere and reached the Earth, but still less than the largest meteorite find, the Hoba meteorite of 60 tonnes.

Impact

At around 10:30 on 12 February 1947, eyewitnesses in the Sikhote-Alin Mountains, Primorye, Soviet Union, observed a large bolide brighter than the sun that came out of the north and descended at an angle of about 41 degrees. The bright flash and the deafening sound of the fall were observed for {{convert|300|km|mi}} around the point of impact not far from Luchegorsk and approximately {{convert|440|km|mi|abbr=on}} northeast of Vladivostok. A smoke trail, estimated at {{convert|32|km|mi|abbr=on}} long, remained in the sky for several hours.

As the meteor, traveling at a speed of about {{convert|14|km/s|mi/s|abbr=on}}, entered the atmosphere, it began to break apart, and the fragments fell together. At an altitude of about {{convert|5.6|km|mi|abbr=on}}, the largest mass apparently broke up in a violent explosion called an air burst.

On November 20, 1957^[3] the Soviet Union issued a stamp for the 10th anniversary of the Sikhote-Alin meteorite shower. It reproduces a painting by P. I. Medvedev, a Soviet artist who witnessed the fall: he was sitting in his window starting a sketch when the fireball appeared, so he immediately began drawing what he saw.^[4]

Orbit

Because the meteor fell during daytime, it was observed by many eyewitnesses. Evaluation of this observational data allowed V. G. Fesenkov, then chairman of the meteorite committee of the USSR Academy of Science, to estimate the meteoroid's orbit before it encountered the Earth. This orbit was ellipse-shaped, with its point of greatest distance from the sun situated within the asteroid belt, similar to many other small bodies crossing the orbit of the Earth. Such an orbit was probably created by collisions within the asteroid belt.

Size

Sikhote-Alin is a massive fall with the overall size of the meteoroid estimated at approximately {{convert|90000|kg|lb|abbr=on}}.^[5] A more recent estimate by Tsvetkov (and others) puts the mass at around {{convert|100000|kg|lb|abbr=on}}.^[6]

Krinov had estimated the post-atmospheric mass of the meteoroid at some {{convert|23000|kg|lb|abbr=on}}.

Strewn field and craters

The strewn field for this meteorite covered an elliptical area of about {{convert|1.3|km2|sqmi|abbr=on}}. Some of the fragments made impact craters, the largest of which was about {{convert|26|m|ft|abbr=on}} across and {{convert|6|m|ft|abbr=on}} deep.^[7] Fragments of the meteorite were also driven into the surrounding trees.

Composition and classification

The Sikhote-Alin meteorite is classified as an iron meteorite belonging to the meteorite group IIAB and with a coarse octahedrite structure. It is composed of approximately 93% iron, 5.9% nickel, 0.42% cobalt, 0.46% phosphorus, and 0.28% sulfur, with trace amounts of germanium and iridium. Minerals present include taenite, plessite, troilite, chromite, kamacite, and schreibersite.^[8]

Specimens

The first type probably broke off the main object early in the descent. These pieces are characterized by regmaglypts (cavities resembling thumb prints) in the surface of each specimen. The second type are fragments which were either torn apart during the atmospheric explosions or blasted apart upon impact on the frozen ground. Most were probably the result of the explosion at {{convert|5.6|km|mi|abbr=on}} altitude.

A large specimen is on display in Moscow. Many other specimens are held by Russian Academy of Science and a great number of smaller specimens have made their way into the collector's market.

See also

References

1. ^¹²{{metbull|23593|Sikhote-Alin}}. [https://web.archive.org/web/20120130073826/http://www.lpi.usra.edu/meteor/metbull.php?code=23593 Archived] from the original on 2012-01-30.
2. ^{{cite book |first=O. Richard |last=Norton |title=Rocks From Space |publisher=Mountain Press |location=Missoula, Montana |year=1998 |page=103 |isbn=0878423028 }}
3. ^{{cite web | url=http://www.pibburns.com/catastro/metstamp.htm | title=Meteorite Stamps and Coins | first=Philip R. "Pib" | last=Burns | work= | publisher= | date= | archiveurl=https://web.archive.org/web/20000121235534/http://www.pibburns.com/catastro/metstamp.htm | archivedate=2000-01-21 | deadurl=no }}
4. ^{{cite web | url=http://www.planetarium.montreal.qc.ca/Information/Expo_Meteorites/Vedettes/sikhotealin_a.html | title=Sikhote Alin | publisher=Planetarium de Montreal | work= | date= | archiveurl=https://web.archive.org/web/20060521024636/http://www.planetarium.montreal.qc.ca/Information/Expo_Meteorites/Vedettes/sikhotealin_a.html | archivedate=2006-05-21 | deadurl=yes }}
5. ^{{cite book |first=O. Richard |last=Norton |first2=Lawrence A. |last2=Chitwood |title=Field Guide to Meteors and Meteorites |publisher=Springer-Verlag |location=London |year=2008 |page=47 |isbn=9781848001572 }}
6. ^¹{{cite journal |url=http://meteoritemag.uark.edu/604.htm |journal=Meteorite Magazine | date=February 1996 |publisher=Arkansas Center for Space and Planetary Sciences, University of Arkansas |title=Sikhote-Alin Revisited |first=Roy |last=Gallant |archiveurl=https://web.archive.org/web/20100612144717/http://meteoritemag.uark.edu/604.htm |archivedate=2010-06-12 |deadurl=yes }}
7. ^{{cite Earth Impact DB | name=Sikhote-Alin | accessdate=2009-08-19 }} {{dead link|date=March 2012}}
8. ^{{Cite book|title=HANDBOOK OF IRON METEORITES Their History, Distribution, Composition and Structure|last=Buchwald|first=Vagn F.|publisher=University of California Press|year=1975|isbn=|location=https://evols.library.manoa.hawaii.edu/handle/10524/36040|pages=Vol 3, Pages 1123–1130|quote=Group lIB. 5.90% Ni, 0.42% Co, 0.46% P, 0.28% S, 52 ppm Ga, 161 ppm Ge , 0.03 ppm Jr.|via=}}