$ i; r/ r# b/ X5 w2 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。6 t: A. |$ {  ^; |9 G7 r
Asteroid impact craters are among the most interesting geological structures on any planet. Many other 公仔箱論壇- w# o8 S3 d4 u$ I2 m7 U3 @
planets and moons in our solar system, including our own moon, are pock-marked with loads of craters. 5.39.217.77:8898* ^9 z! f/ t) I- O
But because Earth has a protective atmosphere and is geologically active — with plate tectonics and volcanic
/ c3 v) g9 {" k; t% t$ t% [% @eruptions, mostly relatively young oceanic crust, and harsh weathering from wind and water — impact 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。( n! p: @+ i0 |0 j: y& v
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. tvb now,tvbnow,bttvb0 j) S( s* A  R% s6 b- y+ V
One well-known example is our own Barringer crater, also known as Meteor Crater, in Arizona. The images here
3 r+ y8 K8 P6 R4 c5.39.217.77:8898show some of the biggest, oldest and most interesting impact craters on the planet.
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1 e8 m. X* K, ctvb now,tvbnow,bttvbAorounga crater, pictured above and below, is one of the best preserved impact craters on Earth, thanks
6 T- H+ s# W7 ^in part to its location in the Sahara Desert in Chad. The 10 mile-wide crater is probably around 350 million 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。$ ^8 T  [. H% F# }& v9 ?* F2 a
years old. The stripes are alternating rock ridges and sand layers, known as yardangs, caused by persistent ; l. v8 `- T% [0 O0 L
unidirectional wind. The image above was taken by astronauts in the International Space Station in July.
/ b1 L& F3 }( I- N4 x  }In the radar image below, taken from the space shuttle in 1994, reveals that Aorounga may be one of two or three craters.; `2 ^' B- I5 I2 H

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The Shoemaker crater in Western Australia, formerly known as the Teague crater, was renamed in honor of the planetary
. ]4 k! ?  r' d; `2 {) D, R公仔箱論壇geologist Eugene Shoemaker for whom the Comet Shoemaker-Levy 9 is also named. The age of the crater unclear, but it . p6 N8 q* K" a# I+ f0 d5 a
could be 1.7 billion years old, which makes it the oldest known impact in Australia. The brightly colored splotches are tvb now,tvbnow,bttvb& u- k' `1 i% }, s' C0 ~
seasonal salt-water lakes. This image was taken by the Landsat 7 satellite.% G# I4 O0 W' i1 x5 j* n
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The Manicouagan Crater in northern Canada is one of the largest impact craters known on Earth. The impact occurred 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。' g7 ], G4 b  q, @4 A% [
around 210 million years ago at the end of the Triassic period and may have caused a mass extinction that killed around / a1 s5 _9 h" @# U5 B1 b  _
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。% U2 I* p! d- K/ \8 s
impact structure. The asteroid that created the crater is thought to have been about three miles wide. Today the lake is a * v3 O( s; I5 s" Y! J* D* D7 S% Z
reservoir and popular salmon fishing location.- ]. c& T3 l7 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 [8 l/ E/ L! b  F- L
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This crazy looking structure in Western Australia is called the Spider crater, for obvious reasons. Geologists determined it was 公仔箱論壇- {5 g7 M& i' s+ H7 _5 \
an impact crater when they found shatter cones, telltale cone-shaped, grooved rocks found only around impacts. The crazy tvb now,tvbnow,bttvb6 K6 l  O; {: f5 n8 ?! n( W; j  F# W2 _
looking legs surrounding the impact are mostly due to erosion of different rock layers. The harder sandstone ridges withstood 6 e$ `+ a1 w7 K6 h5 h' W$ Z; w
the weathering of wind and water better than the softer intervening layers. The crater is somewhere between 600 million tvb now,tvbnow,bttvb* E9 ]. i0 y' ^6 J7 a  f# s' H  R2 A4 A
and 900 million years old and the raised area at its center is around 1,600 feet wide.tvb now,tvbnow,bttvb! c6 x: h) h/ s
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The image above is a false-color image taken by the Advanced Spaceborne Thermal Emission and Reflection Radiometer on 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。  }+ |2 M1 H/ f- K
NASA’s Terra. The true-color image below was captured by Taiwan’s Formost-2 satellite# U7 P# X4 Q' _# q3 g$ ~

  S* t4 C% p+ [6 R$ ?3 i, |+ }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。
* t9 A, R; V# v6 g4 c9 M5.39.217.77:8898TVBNOW 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。, P* d+ e6 K1 H% e3 n% w3 C7 I& Y
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( O6 N3 `; d) w% itvb now,tvbnow,bttvbThe Gosses Bluff crater in Australia’s Northern Territory sits between two mountain ranges. The raised circular feature in the
# H( ]: r! j- p; ]! L' 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。center of the structure is around 2.8 miles across, but the original crater rim was probably at the edge of the surrounding
1 b: P0 W; t2 }7 w- ?1 S+ ^2 K5.39.217.77:8898grayish area. The crater was formed caused by an asteroid impact around 140 million years ago.
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Clearwater Lakes in Quebec, Canada were formed by a pair of asteroid impact craters. The impacts probably occurred 5 N/ n0 \3 r9 k' g! b" @
simultaneously around 290 million years ago. The larger crater measures 22 miles across.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 W( A/ O/ B2 N6 [
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* [8 X8 I) E, c' h; i5.39.217.77:8898The Roter Kamm crater in Namibia is hard to see in visible light, but shows up more clearly with imaging radar. The crater’s $ |" C8 Y  d9 i, ]7 s. p& g9 ?% T
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 boardtvb now,tvbnow,bttvb5 A* y# A4 V  w; \
the space shuttle. Irregular surfaces show up brightly and smooth areas are dark. The white splotch at the bottom of the
4 o3 U, l0 Q7 c% k$ v9 \4 Wtvb 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
, k$ o7 K6 u+ r! fTVBNOW 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。ejected during the impact, the red is limestone outcrop and the green areas are mostly vegetation. The impact occurred 公仔箱論壇# U/ r1 ]+ G' y7 O9 M
around 5 million years ago.
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  f" M- v$ B3 G& g% XThe Lonar crater in Maharashta, India is around 6,000 feet wide and 500 feet deep and contains a saltwater lake.
/ e" U" ]" _% j. Y* @tvb now,tvbnow,bttvbScientists determined the structure was caused by an asteroid through clues such as the presence of maskelynite,
; p8 J) r' w. Ptvb now,tvbnow,bttvba glass that is only formed by extremely high-velocity impacts. The impact occurred around 50,000 years ago.
2 N- Z* O- D0 R0 y0 k& u# T3 hThis image was captured by the Advanced Spaceborne Thermal Emission and Reflection Radiometer on NASA’s tvb now,tvbnow,bttvb0 o4 v7 u: c' L$ u' {! q
Terra satellite. It is a simulated true-color image
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2 X; H8 l9 p! R9 \tvb now,tvbnow,bttvbThe Vredefort Dome in South Africa is possibly the oldest and largest clearly visible asteroid impact on Earth. tvb now,tvbnow,bttvb, y/ Q2 f" q1 a& U' S4 I4 y9 {
The 155-mile crater is approximately 60 miles southwest of Johannesburg and was formed around 2 billion 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。5 I6 {/ L% g6 N4 M: ?1 x! W) ^
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。! X' f* H# f1 `& w, k
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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 公仔箱論壇0 B# z# M2 l9 v' }; V4 ?! U8 O
a 300-mile wide asteroid would look impacting Earth. This event probably would have killed everything on the planet.
! ]4 |8 d, K+ S* yTVBNOW 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。Fortunately, NASA says nothing this big is headed our way anytime soon.