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9 x$ u# e- [/ B- t+ h# {+ Stvb now,tvbnow,bttvbAsteroid impact craters are among the most interesting geological structures on any planet. Many other
% H9 a# Z* [1 t$ @) R3 J0 m公仔箱論壇planets and moons in our solar system, including our own moon, are pock-marked with loads of craters. ! s; g* N( t8 t- W4 o
But because Earth has a protective atmosphere and is geologically active — with plate tectonics and volcanic 公仔箱論壇# D7 ?7 M0 k9 t, B! R
eruptions, mostly relatively young oceanic crust, and harsh weathering from wind and water — impact
, ?; j4 v8 g1 m3 I7 c1 f公仔箱論壇structures don’t last long and can be tough to come by.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 K/ F1 F4 @% w0 [1 E3 _
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But on a few old pieces of continent, especially in arid deserts, the marks of asteroids have been preserved.
# V; J. z9 \2 _/ T; |8 T4 ytvb now,tvbnow,bttvbOne well-known example is our own Barringer crater, also known as Meteor Crater, in Arizona. The images here
7 Y7 i, l0 E3 }+ Eshow some of the biggest, oldest and most interesting impact craters on the planet.公仔箱論壇8 O  r: R  }$ U' `3 {
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Aorounga crater, pictured above and below, is one of the best preserved impact craters on Earth, thanks
0 M% A6 `$ t4 P" N; {4 R2 C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
3 r" s7 y! g* D, z: W9 t$ X% ~www.tvboxnow.comyears old. The stripes are alternating rock ridges and sand layers, known as yardangs, caused by persistent www.tvboxnow.com- i$ H4 D2 j( h& S* m! W' y; H) J
unidirectional wind. The image above was taken by astronauts in the International Space Station in July. 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。. q. \7 A( K$ b+ v" ]5 o" v
In the radar image below, taken from the space shuttle in 1994, reveals that Aorounga may be one of two or three craters.) F- [+ V; H' p6 X$ i
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The Shoemaker crater in Western Australia, formerly known as the Teague crater, was renamed in honor of the planetary
2 i9 R6 S8 B7 i' X/ V3 wtvb now,tvbnow,bttvbgeologist Eugene Shoemaker for whom the Comet Shoemaker-Levy 9 is also named. The age of the crater unclear, but it ) t9 F" {( M  N8 M8 ]5 C
could be 1.7 billion years old, which makes it the oldest known impact in Australia. The brightly colored splotches are # c' p/ h$ i3 X
seasonal salt-water lakes. This image was taken by the Landsat 7 satellite.
$ {# F+ F! v% Xtvb now,tvbnow,bttvb7 e% P" j% g2 `3 R5 u
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; b4 G' X+ N* M1 O& v3 ~' HTVBNOW 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 Manicouagan Crater in northern Canada is one of the largest impact craters known on Earth. The impact occurred
& p9 N5 x* |; ]$ I7 Gwww.tvboxnow.comaround 210 million years ago at the end of the Triassic period and may have caused a mass extinction that killed around 公仔箱論壇: s- e" _% r: o2 n$ n, S, y
60 percent of all species. Though the crater has mostly eroded, Lake Manicouagan outlines what is left of the 43-mile wide 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+ ?+ q) M5 _  ^. N$ o$ W0 S2 U$ F
impact structure. The asteroid that created the crater is thought to have been about three miles wide. Today the lake is a
  n$ X' L7 w. E# dwww.tvboxnow.comreservoir and popular salmon fishing location.
% j9 a+ X0 ]0 J/ s" WTVBNOW 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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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 L& x9 X8 _8 @3 O. D, O

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0 |9 l, q# f; t. e, S7 }1 m; q2 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。This crazy looking structure in Western Australia is called the Spider crater, for obvious reasons. Geologists determined it was
& H* I. _2 T5 ~0 l$ M/ G公仔箱論壇an impact crater when they found shatter cones, telltale cone-shaped, grooved rocks found only around impacts. The crazy 公仔箱論壇- j- h* i3 W. _2 d& O
looking legs surrounding the impact are mostly due to erosion of different rock layers. The harder sandstone ridges withstood
3 x9 f" V) E% F! m8 _& g$ Dthe weathering of wind and water better than the softer intervening layers. The crater is somewhere between 600 million
- o7 I  O0 A  zwww.tvboxnow.comand 900 million years old and the raised area at its center is around 1,600 feet wide.
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% s0 L; I9 M6 H3 w公仔箱論壇The image above is a false-color image taken by the Advanced Spaceborne Thermal Emission and Reflection Radiometer on 公仔箱論壇" q3 |9 ~. H9 w9 f) k
NASA’s Terra. The true-color image below was captured by Taiwan’s Formost-2 satellite6 s$ D$ D- k2 N" q) I
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! @: d5 z3 M/ j& Q3 x1 d8 Dtvb now,tvbnow,bttvb% P7 V$ P1 ~5 V& Q! U9 W( {
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The Gosses Bluff crater in Australia’s Northern Territory sits between two mountain ranges. The raised circular feature in the , e* F" ]/ G; f& {/ x, H1 _
center of the structure is around 2.8 miles across, but the original crater rim was probably at the edge of the surrounding
# }* b- h% ^3 }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。grayish area. The crater was formed caused by an asteroid impact around 140 million years ago.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。! l- Z& g6 ^( s" p5 _$ c  A
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  D. V: N2 [' F2 h, Etvb now,tvbnow,bttvbClearwater Lakes in Quebec, Canada were formed by a pair of asteroid impact craters. The impacts probably occurred www.tvboxnow.com8 E& f1 d9 B8 o( m
simultaneously around 290 million years ago. The larger crater measures 22 miles across.6 g; ]" f, P: n, |! z1 C
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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 tvb now,tvbnow,bttvb" o0 M  Q7 K( a" T- _1 y
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 c1 T/ U0 F5 G" `' e公仔箱論壇 the space shuttle. Irregular surfaces show up brightly and smooth areas are dark. The white splotch at the bottom of the
: `) ~6 X. k$ ?1 O: _0 _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 ' D, c( b7 }2 A: o- z; ]
ejected during the impact, the red is limestone outcrop and the green areas are mostly vegetation. The impact occurred
  y7 Z4 o& M0 @" zwww.tvboxnow.comaround 5 million years ago.
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' e& @+ D) X+ f* _/ K/ V0 ~7 k+ mtvb now,tvbnow,bttvbThe Lonar crater in Maharashta, India is around 6,000 feet wide and 500 feet deep and contains a saltwater lake. www.tvboxnow.com  `1 V9 F( y( j8 B1 q" s# k5 k
Scientists determined the structure was caused by an asteroid through clues such as the presence of maskelynite,
9 k4 I: f1 F3 |& S* m# W; jtvb now,tvbnow,bttvba glass that is only formed by extremely high-velocity impacts. The impact occurred around 50,000 years ago.
2 L+ H, d3 P& @8 D  W5 F- B) k  {www.tvboxnow.comThis image was captured by the Advanced Spaceborne Thermal Emission and Reflection Radiometer on NASA’s tvb now,tvbnow,bttvb( h2 o- q! \& o, E! I+ a
Terra satellite. It is a simulated true-color imagetvb now,tvbnow,bttvb: V8 [) K) J% P9 s+ P
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; B) R3 `7 M, W8 C) A: O) ktvb now,tvbnow,bttvbThe Vredefort Dome in South Africa is possibly the oldest and largest clearly visible asteroid impact on Earth. tvb now,tvbnow,bttvb5 H  I0 l: K, ?
The 155-mile crater is approximately 60 miles southwest of Johannesburg and was formed around 2 billion years ago.
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3 g2 }6 q) K5 e1 N# KTVBNOW 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。, l; O- z! I0 E7 N4 x( B) o, G$ J
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 I0 o5 F$ A: y: L) i8 H

# s2 ~9 O, W/ x) jArtist’s rendering of a space object or phenomenon, so we couldn’t resist this beauty. This is one man’s idea of what
% x8 R! X( I  \; D1 VTVBNOW 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。a 300-mile wide asteroid would look impacting Earth. This event probably would have killed everything on the planet. www.tvboxnow.com" A/ ~2 X7 [/ j$ \- r. \+ `9 h
Fortunately, NASA says nothing this big is headed our way anytime soon.