Asteroid Impact Craters on Earth as Seen From Space

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- e  P+ O0 [! e8 D7 UTVBNOW 含有熱門話題，最新最快電視，軟體，遊戲，電影，動漫及日常生活及興趣交流等資訊。Asteroid impact craters are among the most interesting geological structures on any planet. Many other
- |/ C) R% Q: f$ x! n3 b' _0 Etvb now,tvbnow,bttvbplanets and moons in our solar system, including our own moon, are pock-marked with loads of craters. 5.39.217.77:8898$ w4 h) I* ^. n3 d0 c' K+ r. D
But because Earth has a protective atmosphere and is geologically active — with plate tectonics and volcanic
4 n8 L7 l& {+ X% l公仔箱論壇eruptions, mostly relatively young oceanic crust, and harsh weathering from wind and water — impact 5.39.217.77:8898% v7 d/ @4 h- u: n& v2 _
structures don’t last long and can be tough to come by.
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But on a few old pieces of continent, especially in arid deserts, the marks of asteroids have been preserved. ( m/ s1 D3 `% ~  l2 l2 m7 n
One well-known example is our own Barringer crater, also known as Meteor Crater, in Arizona. The images here
+ n% L8 G' ^" ^, B& ~+ _% |5 Vtvb now,tvbnow,bttvbshow some of the biggest, oldest and most interesting impact craters on the planet.公仔箱論壇4 S- v1 c% p6 F
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Aorounga crater, pictured above and below, is one of the best preserved impact craters on Earth, thanks
1 b# ~% z" T7 I6 Z& B1 nTVBNOW 含有熱門話題，最新最快電視，軟體，遊戲，電影，動漫及日常生活及興趣交流等資訊。in part to its location in the Sahara Desert in Chad. The 10 mile-wide crater is probably around 350 million tvb now,tvbnow,bttvb# s  j- y) a' I$ n  l
years old. The stripes are alternating rock ridges and sand layers, known as yardangs, caused by persistent : B- t9 J- Q9 j
unidirectional wind. The image above was taken by astronauts in the International Space Station in July. tvb now,tvbnow,bttvb! v0 g4 C" U! F) v3 n
In the radar image below, taken from the space shuttle in 1994, reveals that Aorounga may be one of two or three craters.公仔箱論壇: x2 d( b6 a4 z. O6 Z( n

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The Shoemaker crater in Western Australia, formerly known as the Teague crater, was renamed in honor of the planetary
) E4 a0 Y7 V2 z3 {  D9 R5.39.217.77:8898geologist Eugene Shoemaker for whom the Comet Shoemaker-Levy 9 is also named. The age of the crater unclear, but it
! J/ e) c! R% e5.39.217.77:8898could be 1.7 billion years old, which makes it the oldest known impact in Australia. The brightly colored splotches are 9 i+ t# z/ F. A% I( ~( k4 X
seasonal salt-water lakes. This image was taken by the Landsat 7 satellite.
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The Manicouagan Crater in northern Canada is one of the largest impact craters known on Earth. The impact occurred
  _1 t* b; @& Naround 210 million years ago at the end of the Triassic period and may have caused a mass extinction that killed around
/ |! t: {: P' L, ?0 o) j- M* X公仔箱論壇60 percent of all species. Though the crater has mostly eroded, Lake Manicouagan outlines what is left of the 43-mile wide
/ B1 p7 X2 {; \impact structure. The asteroid that created the crater is thought to have been about three miles wide. Today the lake is a TVBNOW 含有熱門話題，最新最快電視，軟體，遊戲，電影，動漫及日常生活及興趣交流等資訊。6 V+ L3 z6 l7 r
reservoir and popular salmon fishing location.
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This crazy looking structure in Western Australia is called the Spider crater, for obvious reasons. Geologists determined it was tvb now,tvbnow,bttvb6 h  H. {  d! ~. o' _; e0 Y6 n
an impact crater when they found shatter cones, telltale cone-shaped, grooved rocks found only around impacts. The crazy
2 }( T8 |& M# `/ w3 L2 z8 _9 W5.39.217.77:8898looking legs surrounding the impact are mostly due to erosion of different rock layers. The harder sandstone ridges withstood
1 m% L1 ~' N) \the weathering of wind and water better than the softer intervening layers. The crater is somewhere between 600 million
7 |! d& [3 m" t. I9 h公仔箱論壇and 900 million years old and the raised area at its center is around 1,600 feet wide.. V$ {8 P" E& f8 \

$ g( H# T) V: i! B; `' ^3 z* _公仔箱論壇The image above is a false-color image taken by the Advanced Spaceborne Thermal Emission and Reflection Radiometer on * W9 }4 \6 `1 v- M- y8 d4 ^
NASA’s Terra. The true-color image below was captured by Taiwan’s Formost-2 satellitetvb now,tvbnow,bttvb8 j' [' X! t5 F: z2 F$ W, o  X' R
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TVBNOW 含有熱門話題，最新最快電視，軟體，遊戲，電影，動漫及日常生活及興趣交流等資訊。3 @. U8 r# C8 o
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& n# v0 u7 `, w9 C- f( @TVBNOW 含有熱門話題，最新最快電視，軟體，遊戲，電影，動漫及日常生活及興趣交流等資訊。The Gosses Bluff crater in Australia’s Northern Territory sits between two mountain ranges. The raised circular feature in the
: o* _( y6 k% k( [center of the structure is around 2.8 miles across, but the original crater rim was probably at the edge of the surrounding
" n) f! @4 K( f: b; ?" Ograyish area. The crater was formed caused by an asteroid impact around 140 million years ago.tvb now,tvbnow,bttvb: |6 H7 K5 _, ]# Y

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0 {; X# h. e7 qClearwater Lakes in Quebec, Canada were formed by a pair of asteroid impact craters. The impacts probably occurred 公仔箱論壇- I" T1 I8 h/ w# x/ }
simultaneously around 290 million years ago. The larger crater measures 22 miles across.
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The Roter Kamm crater in Namibia is hard to see in visible light, but shows up more clearly with imaging radar. The crater’s
5 C3 p$ h2 a# |4 h5 R, Ltvb now,tvbnow,bttvb1.5 mile-wide rim stands out as a bright ring in the lower left of the image, which was taken by a radar instrument on board) p$ S- K4 a: M$ ?3 b+ m
the space shuttle. Irregular surfaces show up brightly and smooth areas are dark. The white splotch at the bottom of the tvb now,tvbnow,bttvb4 ^7 Z" B$ l1 O& F
photo is a rocky hill, the darkest areas are wind-blown sand dunes, the blue around the crater’s rim may be material that was tvb now,tvbnow,bttvb3 |+ b8 h% [5 x5 A/ v! p
ejected during the impact, the red is limestone outcrop and the green areas are mostly vegetation. The impact occurred
: C2 L  D3 v1 a: xaround 5 million years ago.
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7 k; w& m0 K! F: P2 P/ V9 P, t公仔箱論壇The Lonar crater in Maharashta, India is around 6,000 feet wide and 500 feet deep and contains a saltwater lake.
. _6 ~% o; }4 H/ A2 N0 wScientists determined the structure was caused by an asteroid through clues such as the presence of maskelynite, tvb now,tvbnow,bttvb. L2 Q0 @7 C! c
a glass that is only formed by extremely high-velocity impacts. The impact occurred around 50,000 years ago.
8 G6 X/ G- q) xTVBNOW 含有熱門話題，最新最快電視，軟體，遊戲，電影，動漫及日常生活及興趣交流等資訊。This image was captured by the Advanced Spaceborne Thermal Emission and Reflection Radiometer on NASA’s / f/ H4 o+ |* o% A$ W$ @( d
Terra satellite. It is a simulated true-color image
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% Q2 F2 E0 N4 w$ ztvb now,tvbnow,bttvbThe Vredefort Dome in South Africa is possibly the oldest and largest clearly visible asteroid impact on Earth.
$ }6 q1 p6 s* ^. V: V0 Wtvb now,tvbnow,bttvbThe 155-mile crater is approximately 60 miles southwest of Johannesburg and was formed around 2 billion years ago.tvb now,tvbnow,bttvb1 D$ [# V/ C# [# x' `/ \

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: A6 Q- p* f( o5 j( g" Ftvb now,tvbnow,bttvbArtist’s rendering of a space object or phenomenon, so we couldn’t resist this beauty. This is one man’s idea of what
. @5 J8 ]2 }2 f; e1 G0 ra 300-mile wide asteroid would look impacting Earth. This event probably would have killed everything on the planet. 0 x$ ?9 Q6 m+ s- f0 `; r3 {# I
Fortunately, NASA says nothing this big is headed our way anytime soon.