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Asteroid impact craters are among the most interesting geological structures on any planet. Many other   J$ [. ]( V$ w4 l& @: h! k
planets and moons in our solar system, including our own moon, are pock-marked with loads of craters. 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。; u/ i. y! h& E* e( y- g3 {; |- }8 E- q
But because Earth has a protective atmosphere and is geologically active — with plate tectonics and volcanic tvb now,tvbnow,bttvb  c+ Q" ]& L( `& e) ~% r
eruptions, mostly relatively young oceanic crust, and harsh weathering from wind and water — impact
8 t( @* w& _# F* O" G+ [3 Ptvb now,tvbnow,bttvbstructures 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. : {8 [+ Y9 h/ @2 E' h1 e7 }
One well-known example is our own Barringer crater, also known as Meteor Crater, in Arizona. The images here
: R+ t2 N; r6 `: l* D' `$ l( U. M公仔箱論壇show some of the biggest, oldest and most interesting impact craters on the planet.0 `7 v  v2 u* X; V5 L" P& v  C
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Aorounga crater, pictured above and below, is one of the best preserved impact craters on Earth, thanks
$ |& E4 l; U* @  F4 Gin part to its location in the Sahara Desert in Chad. The 10 mile-wide crater is probably around 350 million 公仔箱論壇& D7 K* G- H1 ~- L. a
years old. The stripes are alternating rock ridges and sand layers, known as yardangs, caused by persistent
) e4 D  S) `$ W# cTVBNOW 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。unidirectional wind. The image above was taken by astronauts in the International Space Station in July. 公仔箱論壇4 O; K( n! n4 f- i* D3 p
In the radar image below, taken from the space shuttle in 1994, reveals that Aorounga may be one of two or three craters., X. U- L6 M/ j. _% b: h

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! J2 A- \6 X8 {; o' ztvb now,tvbnow,bttvbThe Shoemaker crater in Western Australia, formerly known as the Teague crater, was renamed in honor of the planetary
' I3 G: }4 |5 T" `! ntvb now,tvbnow,bttvbgeologist Eugene Shoemaker for whom the Comet Shoemaker-Levy 9 is also named. The age of the crater unclear, but it
* D; i! N! P4 rwww.tvboxnow.comcould be 1.7 billion years old, which makes it the oldest known impact in Australia. The brightly colored splotches are
& ~% r$ S/ l9 F3 v  Hwww.tvboxnow.comseasonal 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
4 |1 I& U! [) b2 j* `$ b  varound 210 million years ago at the end of the Triassic period and may have caused a mass extinction that killed around
$ a' L' ^  ~8 ?, Ntvb now,tvbnow,bttvb60 percent of all species. Though the crater has mostly eroded, Lake Manicouagan outlines what is left of the 43-mile wide 公仔箱論壇- r. p$ B/ a) j& m
impact structure. The asteroid that created the crater is thought to have been about three miles wide. Today the lake is a
  T( D3 Y& q- t, D6 y& fwww.tvboxnow.comreservoir and popular salmon fishing location.
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  d4 K& l/ M0 I7 Y) t' fwww.tvboxnow.comThis crazy looking structure in Western Australia is called the Spider crater, for obvious reasons. Geologists determined it was 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。) y& B( p3 c: e: F
an impact crater when they found shatter cones, telltale cone-shaped, grooved rocks found only around impacts. The crazy
+ f. @4 W7 U: w* blooking legs surrounding the impact are mostly due to erosion of different rock layers. The harder sandstone ridges withstood $ ~  ?$ q: ]$ _/ K) P4 n- B( Y/ y1 c
the weathering of wind and water better than the softer intervening layers. The crater is somewhere between 600 million
# z3 k- d. A& P6 m- E* I) ywww.tvboxnow.comand 900 million years old and the raised area at its center is around 1,600 feet wide.
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The image above is a false-color image taken by the Advanced Spaceborne Thermal Emission and Reflection Radiometer on ; X: `  x  c) l5 a
NASA’s Terra. The true-color image below was captured by Taiwan’s Formost-2 satellitewww.tvboxnow.com2 P2 w) Y( u  Z: [3 G8 Q" `

( l* ?; |$ t* P, |$ y2 |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。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。9 H9 E  o3 j" c4 C/ E

3 V5 B! b2 z2 c! y6 O& Dwww.tvboxnow.comtvb now,tvbnow,bttvb/ z0 N" ]& X) q' x

. [& J, P5 A' E; JTVBNOW 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
( v; T, T3 @. Z4 u$ N公仔箱論壇center of the structure is around 2.8 miles across, but the original crater rim was probably at the edge of the surrounding
8 o2 e9 ^5 f& y5 g& 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。grayish area. The crater was formed caused by an asteroid impact around 140 million years ago.' S4 o8 U9 Q( N' O
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。. S) g! e2 z1 M- ^- D$ E  G6 _: z
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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。. ]1 O6 |4 u4 f: S. e; q6 ?/ [
Clearwater Lakes in Quebec, Canada were formed by a pair of asteroid impact craters. The impacts probably occurred
- z( E/ z* w* O( f9 R$ ktvb now,tvbnow,bttvbsimultaneously around 290 million years ago. The larger crater measures 22 miles across.
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+ o- g5 Z% r# N. xtvb now,tvbnow,bttvbThe Roter Kamm crater in Namibia is hard to see in visible light, but shows up more clearly with imaging radar. The crater’s www.tvboxnow.com1 Q$ {$ p" I  z$ p: W( I7 U0 T9 D
1.5 mile-wide rim stands out as a bright ring in the lower left of the image, which was taken by a radar instrument on boardwww.tvboxnow.com$ v; \" n% m7 g, z
the space shuttle. Irregular surfaces show up brightly and smooth areas are dark. The white splotch at the bottom of the
& Z. `/ {& B; mtvb now,tvbnow,bttvbphoto is a rocky hill, the darkest areas are wind-blown sand dunes, the blue around the crater’s rim may be material that was 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。0 L# r" s7 J6 k! ^# f& j
ejected during the impact, the red is limestone outcrop and the green areas are mostly vegetation. The impact occurred
' m  X6 z1 \  ~( c) d3 m& V公仔箱論壇around 5 million years ago.
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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。; F1 l% ~# X9 C

: h) j% u# Q! n$ o  r4 v% R  d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.
- M. {9 m% T, i$ Y9 Z9 nScientists determined the structure was caused by an asteroid through clues such as the presence of maskelynite, 公仔箱論壇4 `3 X9 v) |: {1 m) v) n2 z
a glass that is only formed by extremely high-velocity impacts. The impact occurred around 50,000 years ago.
& q$ ~. r: u/ Q! F: I, a4 j2 t3 w) WThis image was captured by the Advanced Spaceborne Thermal Emission and Reflection Radiometer on NASA’s , h0 Y/ [2 p9 s, o4 z
Terra satellite. It is a simulated true-color image
3 y: C7 x) W" o, ~! ?; }$ b公仔箱論壇公仔箱論壇  T: v& p; [* r7 M$ x% h
tvb now,tvbnow,bttvb8 S* Z/ R' y5 K8 Z, }

# l1 Z, h! i& Y; M6 ]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 Vredefort Dome in South Africa is possibly the oldest and largest clearly visible asteroid impact on Earth. 公仔箱論壇/ N& m  Y2 N6 H" L: a
The 155-mile crater is approximately 60 miles southwest of Johannesburg and was formed around 2 billion years ago.3 u$ d6 ^. a: R3 v, p+ s( t

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Artist’s rendering of a space object or phenomenon, so we couldn’t resist this beauty. This is one man’s idea of what 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 M2 ~$ Y, z% d. e# Y! d0 M" M
a 300-mile wide asteroid would look impacting Earth. This event probably would have killed everything on the planet. 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。$ g( L8 e8 k6 s; w/ c
Fortunately, NASA says nothing this big is headed our way anytime soon.