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。- M, T1 L* q$ V) x
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Asteroid impact craters are among the most interesting geological structures on any planet. Many other
5 P. U% ]4 }4 u# X; f公仔箱論壇planets and moons in our solar system, including our own moon, are pock-marked with loads of craters. tvboxnow.com+ d3 [* S5 \0 p# ~% \0 z
But because Earth has a protective atmosphere and is geologically active — with plate tectonics and volcanic tvb now,tvbnow,bttvb2 d# q& C) ]0 s% B' L/ z* @) X
eruptions, mostly relatively young oceanic crust, and harsh weathering from wind and water — impact
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But on a few old pieces of continent, especially in arid deserts, the marks of asteroids have been preserved. 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。4 E/ P9 T; d% ~. ]* R" ?, v
One well-known example is our own Barringer crater, also known as Meteor Crater, in Arizona. The images here
, @, W  y: }. u4 }5 _show some of the biggest, oldest and most interesting impact craters on the planet.
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Aorounga crater, pictured above and below, is one of the best preserved impact craters on Earth, thanks 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 E9 m! a& S8 ^& @3 s- C1 H
in part to its location in the Sahara Desert in Chad. The 10 mile-wide crater is probably around 350 million
6 S7 \- m; d( ~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。years old. The stripes are alternating rock ridges and sand layers, known as yardangs, caused by persistent
* l' l8 }0 H2 d1 s公仔箱論壇unidirectional wind. The image above was taken by astronauts in the International Space Station in July.
+ [' B: W$ U$ J: K: a* Xtvb now,tvbnow,bttvbIn the radar image below, taken from the space shuttle in 1994, reveals that Aorounga may be one of two or three craters.tvb now,tvbnow,bttvb+ W6 Q+ j7 P" m

7 B1 v3 `; L9 itvboxnow.comTVBNOW 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 I/ `' f/ H% p' P
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The Shoemaker crater in Western Australia, formerly known as the Teague crater, was renamed in honor of the planetary : U# Y1 V/ L* g3 b6 L8 L
geologist Eugene Shoemaker for whom the Comet Shoemaker-Levy 9 is also named. The age of the crater unclear, but it tvboxnow.com  ~9 k! h  w3 y; Y
could be 1.7 billion years old, which makes it the oldest known impact in Australia. The brightly colored splotches are
( D$ ?( Z! n+ G9 B5 A公仔箱論壇seasonal salt-water lakes. This image was taken by the Landsat 7 satellite.tvb now,tvbnow,bttvb7 a6 @2 S1 L! x$ N- l7 g

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The Manicouagan Crater in northern Canada is one of the largest impact craters known on Earth. The impact occurred
0 G7 \  K  n8 D9 |. a" |/ \tvb now,tvbnow,bttvbaround 210 million years ago at the end of the Triassic period and may have caused a mass extinction that killed around
% F; p9 H4 h- I  R& B2 ltvb now,tvbnow,bttvb60 percent of all species. Though the crater has mostly eroded, Lake Manicouagan outlines what is left of the 43-mile wide
0 W' [+ a/ ~! D% v$ dtvb now,tvbnow,bttvbimpact structure. The asteroid that created the crater is thought to have been about three miles wide. Today the lake is a
$ d/ L6 ?) K" P. d6 `tvb now,tvbnow,bttvbreservoir and popular salmon fishing location.+ j0 B5 V) z0 o: v# ?
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This crazy looking structure in Western Australia is called the Spider crater, for obvious reasons. Geologists determined it was
3 V" I& Q# P* s% X  w$ H& Etvboxnow.coman impact crater when they found shatter cones, telltale cone-shaped, grooved rocks found only around impacts. The crazy $ @) F' @! M4 r8 T
looking legs surrounding the impact are mostly due to erosion of different rock layers. The harder sandstone ridges withstood
7 N1 @/ u( l- `% c6 M6 dthe weathering of wind and water better than the softer intervening layers. The crater is somewhere between 600 million 公仔箱論壇! v- \1 q7 u& T) C) N% i! V
and 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. Z3 H8 M" g! G: 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。NASA’s Terra. The true-color image below was captured by Taiwan’s Formost-2 satellite
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' i4 l; w: R" l1 J- ttvboxnow.comThe Gosses Bluff crater in Australia’s Northern Territory sits between two mountain ranges. The raised circular feature in the & n+ ~% u* o* z2 D: \" M
center of the structure is around 2.8 miles across, but the original crater rim was probably at the edge of the surrounding
" D6 m4 |1 J2 `' pgrayish area. The crater was formed caused by an asteroid impact around 140 million years ago.tvboxnow.com, P' M5 p7 |+ v, V
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% ^0 _& E4 b2 V% z3 mClearwater Lakes in Quebec, Canada were formed by a pair of asteroid impact craters. The impacts probably occurred 公仔箱論壇: w! T2 g9 \+ p5 n
simultaneously around 290 million years ago. The larger crater measures 22 miles across.+ `9 i/ B" V2 `. m2 @" X
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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 9 W$ C: p8 q4 l( o
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' f, _6 v! P! |
the space shuttle. Irregular surfaces show up brightly and smooth areas are dark. The white splotch at the bottom of the
) {5 [4 R- [7 P' s, Ztvboxnow.comphoto is a rocky hill, the darkest areas are wind-blown sand dunes, the blue around the crater’s rim may be material that was
# d7 `& e& b8 l# L+ b0 O7 ]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。ejected during the impact, the red is limestone outcrop and the green areas are mostly vegetation. The impact occurred 7 _3 f; {$ i: c8 O% S6 l8 i- r
around 5 million years ago.
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The Lonar crater in Maharashta, India is around 6,000 feet wide and 500 feet deep and contains a saltwater lake.
& Q' o8 M. \7 v, E7 O公仔箱論壇Scientists determined the structure was caused by an asteroid through clues such as the presence of maskelynite, & Y% q' Y* S/ |5 U2 v  m
a glass that is only formed by extremely high-velocity impacts. The impact occurred around 50,000 years ago. 公仔箱論壇9 ?. n9 z3 e% M8 R: H
This image was captured by the Advanced Spaceborne Thermal Emission and Reflection Radiometer on NASA’s . u# B0 W6 W+ n. P) K" `/ v
Terra satellite. It is a simulated true-color imagetvboxnow.com3 u; U+ O9 W* K6 H
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The Vredefort Dome in South Africa is possibly the oldest and largest clearly visible asteroid impact on Earth. + ?4 A( H# l% O
The 155-mile crater is approximately 60 miles southwest of Johannesburg and was formed around 2 billion years ago.* W; Z0 ^! _% U& K' Z
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2 B* ^) P6 O, y8 o6 s- O2 O* uArtist’s rendering of a space object or phenomenon, so we couldn’t resist this beauty. This is one man’s idea of what
- T9 G2 y4 h3 v7 C) r% wtvb now,tvbnow,bttvba 300-mile wide asteroid would look impacting Earth. This event probably would have killed everything on the planet. 公仔箱論壇- u# Q1 K; [  J, S( m" q8 x6 ]) o
Fortunately, NASA says nothing this big is headed our way anytime soon.