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) k* P2 t7 ^6 R0 g% ]! b4 iTVBNOW 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 公仔箱論壇8 I& i, p, a1 Q% n- d0 G) k$ K
planets and moons in our solar system, including our own moon, are pock-marked with loads of craters.
2 g! R: C" s# @9 V$ }: s6 ~% _tvboxnow.comBut because Earth has a protective atmosphere and is geologically active — with plate tectonics and volcanic tvboxnow.com, A- l4 o( P' B) q
eruptions, mostly relatively young oceanic crust, and harsh weathering from wind and water — impact tvboxnow.com  d2 Z9 ?5 A4 [
structures don’t last long and can be tough to come by." s% y- F' ?2 |4 r
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But on a few old pieces of continent, especially in arid deserts, the marks of asteroids have been preserved.
. X' C' y* P$ |3 E3 H' Ttvboxnow.comOne well-known example is our own Barringer crater, also known as Meteor Crater, in Arizona. The images here
- s6 l4 ~" v1 G) R6 |- S; ^+ ?, _show some of the biggest, oldest and most interesting impact craters on the planet.
4 }& e* \/ P: }tvb now,tvbnow,bttvbTVBNOW 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。* d0 C& K1 U0 k8 d3 w# ?8 w
Aorounga crater, pictured above and below, is one of the best preserved impact craters on Earth, thanks
$ d, A5 w+ ~8 N! i  B+ i: z& g- u公仔箱論壇in part to its location in the Sahara Desert in Chad. The 10 mile-wide crater is probably around 350 million
* Q. w9 D# g: X. Mtvboxnow.comyears old. The stripes are alternating rock ridges and sand layers, known as yardangs, caused by persistent tvb now,tvbnow,bttvb& J2 \. r- d9 \" d& f0 o7 n
unidirectional wind. The image above was taken by astronauts in the International Space Station in July. % `: {9 w9 V/ M0 b
In the radar image below, taken from the space shuttle in 1994, reveals that Aorounga may be one of two or three craters.
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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。; E! ^7 L6 X" _+ S5 D5 P6 z
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The Shoemaker crater in Western Australia, formerly known as the Teague crater, was renamed in honor of the planetary tvboxnow.com/ r2 d9 r' e0 o+ k8 u1 G
geologist Eugene Shoemaker for whom the Comet Shoemaker-Levy 9 is also named. The age of the crater unclear, but it
, |1 H* s5 `; r* L4 tTVBNOW 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。could be 1.7 billion years old, which makes it the oldest known impact in Australia. The brightly colored splotches are
7 X" P9 x" X$ I- X% T7 ~tvboxnow.comseasonal salt-water lakes. This image was taken by the Landsat 7 satellite.tvb now,tvbnow,bttvb1 F3 A; u0 Y- L! S! ~

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. ~$ F: Q5 g& nThe Manicouagan Crater in northern Canada is one of the largest impact craters known on Earth. The impact occurred
% W3 t' R: J& A9 ]+ Q4 aTVBNOW 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。around 210 million years ago at the end of the Triassic period and may have caused a mass extinction that killed around tvb now,tvbnow,bttvb5 z- L$ P, K1 k2 P2 Q
60 percent of all species. Though the crater has mostly eroded, Lake Manicouagan outlines what is left of the 43-mile wide tvb now,tvbnow,bttvb  E6 W! E+ u2 v! H4 C/ `# S9 B% r
impact structure. The asteroid that created the crater is thought to have been about three miles wide. Today the lake is a 公仔箱論壇! p7 }$ F5 k- c' G. N6 E
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
, i, Q. o7 v5 t7 r* j1 k5 K9 ran impact crater when they found shatter cones, telltale cone-shaped, grooved rocks found only around impacts. The crazy tvboxnow.com6 ?4 _6 c* M  L5 ?! J' @5 n
looking legs surrounding the impact are mostly due to erosion of different rock layers. The harder sandstone ridges withstood 7 C9 U# w: l6 m6 @2 }& J
the weathering of wind and water better than the softer intervening layers. The crater is somewhere between 600 million
: H: C) l8 J! I% Ztvboxnow.comand 900 million years old and the raised area at its center is around 1,600 feet wide.
+ R0 B8 `2 B5 ~' y' A, M" aTVBNOW 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。! b2 G1 J$ c+ s4 p8 H
The image above is a false-color image taken by the Advanced Spaceborne Thermal Emission and Reflection Radiometer on
% K6 N8 \- Y+ V  DTVBNOW 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。NASA’s Terra. The true-color image below was captured by Taiwan’s Formost-2 satellitetvboxnow.com1 |$ ^( c( w/ ~$ F8 o$ q

1 K( k! C) @  I/ l. ~  w( v- \+ n4 GTVBNOW 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。
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$ {8 A6 N, Y6 e( \( ~$ O$ n公仔箱論壇The Gosses Bluff crater in Australia’s Northern Territory sits between two mountain ranges. The raised circular feature in the 公仔箱論壇; K0 D* N0 r* @1 w' G( u
center of the structure is around 2.8 miles across, but the original crater rim was probably at the edge of the surrounding 3 a4 A* {. X/ A( y
grayish area. The crater was formed caused by an asteroid impact around 140 million years ago.
) M9 d$ O8 G8 y4 k( eTVBNOW 含有熱門話題，最新最快電視，軟體，遊戲，電影，動漫及日常生活及興趣交流等資訊。% w: {* Q9 N) Q! P6 k1 |5 H8 k
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TVBNOW 含有熱門話題，最新最快電視，軟體，遊戲，電影，動漫及日常生活及興趣交流等資訊。/ I  o' O; |7 s
Clearwater Lakes in Quebec, Canada were formed by a pair of asteroid impact craters. The impacts probably occurred 公仔箱論壇; ^- \) U7 A2 [5 D5 _
simultaneously around 290 million years ago. The larger crater measures 22 miles across.
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" @; z# s; r  M' RTVBNOW 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。
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- V0 O& [1 U7 ]" aTVBNOW 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 Roter Kamm crater in Namibia is hard to see in visible light, but shows up more clearly with imaging radar. The crater’s
9 P% c6 {3 R) |9 h. lTVBNOW 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。1.5 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
3 ]( |/ G5 t4 a( p the space shuttle. Irregular surfaces show up brightly and smooth areas are dark. The white splotch at the bottom of the tvb now,tvbnow,bttvb: L3 E& w& @$ w, ]1 v: p: N" V9 x
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 * U5 d$ y% L  R9 O2 n7 P) I
ejected during the impact, the red is limestone outcrop and the green areas are mostly vegetation. The impact occurred ! x' J6 l6 }- \2 q
around 5 million years ago.tvb now,tvbnow,bttvb$ o# J7 V% y  u6 I4 I1 x% ]
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: R0 ]' A- Y/ T/ e7 qThe Lonar crater in Maharashta, India is around 6,000 feet wide and 500 feet deep and contains a saltwater lake. ( u  {: x* i; X% ]) ?: u
Scientists determined the structure was caused by an asteroid through clues such as the presence of maskelynite,
( \# A  ^6 @6 C5 dtvboxnow.coma glass that is only formed by extremely high-velocity impacts. The impact occurred around 50,000 years ago.
7 \7 H/ B: o1 t9 q3 Y( Y8 Q% S  bThis image was captured by the Advanced Spaceborne Thermal Emission and Reflection Radiometer on NASA’s tvb now,tvbnow,bttvb6 Y. e0 P6 h" n6 H9 X5 p
Terra satellite. It is a simulated true-color image
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- w7 u* |1 w4 Q5 |公仔箱論壇The Vredefort Dome in South Africa is possibly the oldest and largest clearly visible asteroid impact on Earth. tvboxnow.com! q) A; b0 l* E4 A: N, S
The 155-mile crater is approximately 60 miles southwest of Johannesburg and was formed around 2 billion years ago.
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6 k- h4 _$ e; C9 _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。
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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
& U3 W+ I/ L. X公仔箱論壇a 300-mile wide asteroid would look impacting Earth. This event probably would have killed everything on the planet.
1 d/ N. ~0 r6 r  o公仔箱論壇Fortunately, NASA says nothing this big is headed our way anytime soon.