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+ s* v+ {, V4 b! M1 TAsteroid impact craters are among the most interesting geological structures on any planet. Many other
& p+ Q, B. m% w! E: PTVBNOW 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。planets and moons in our solar system, including our own moon, are pock-marked with loads of craters.
4 [2 `$ x1 `/ ktvb now,tvbnow,bttvbBut because Earth has a protective atmosphere and is geologically active — with plate tectonics and volcanic 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 \3 P5 c) E% e3 E6 K9 t( N
eruptions, mostly relatively young oceanic crust, and harsh weathering from wind and water — impact
7 Q% G( P- U. z公仔箱論壇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. os.tvboxnow.com. I3 Y6 L" [/ o8 F! l! c
One well-known example is our own Barringer crater, also known as Meteor Crater, in Arizona. The images here tvb now,tvbnow,bttvb& [; ^7 `7 {1 p2 A/ M; l" _: ]7 C
show some of the biggest, oldest and most interesting impact craters on the planet.
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2 E7 @( ~  [4 s  [4 QTVBNOW 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。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 _9 H: u! w8 N- S0 f* M* n4 G
in part to its location in the Sahara Desert in Chad. The 10 mile-wide crater is probably around 350 million % M! u7 H, F, F) q
years old. The stripes are alternating rock ridges and sand layers, known as yardangs, caused by persistent : e* |, W* ?7 Q8 A  W
unidirectional wind. The image above was taken by astronauts in the International Space Station in July. 公仔箱論壇5 v+ K$ x! \( f5 M) C) p
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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$ e$ b- G  [4 h! K, HThe Shoemaker crater in Western Australia, formerly known as the Teague crater, was renamed in honor of the planetary 8 `9 N. t" K( L" S
geologist Eugene Shoemaker for whom the Comet Shoemaker-Levy 9 is also named. The age of the crater unclear, but it
7 w5 h7 S  X. e+ o) 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。could be 1.7 billion years old, which makes it the oldest known impact in Australia. The brightly colored splotches are os.tvboxnow.com, g8 J- A! J" T( [
seasonal salt-water lakes. This image was taken by the Landsat 7 satellite.
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3 `: j$ ~+ m' @' t公仔箱論壇% E" W7 h. o5 F& f( v7 _! v
The Manicouagan Crater in northern Canada is one of the largest impact craters known on Earth. The impact occurred 公仔箱論壇& A* T# J6 H! z3 d8 d, I
around 210 million years ago at the end of the Triassic period and may have caused a mass extinction that killed around
( U5 V9 ?. q2 y. U+ A- N60 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% M4 c& H: S4 Y6 f; m' G; B9 I
impact structure. The asteroid that created the crater is thought to have been about three miles wide. Today the lake is a / v% O3 Q+ p( Z/ F* I
reservoir and popular salmon fishing location.
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! v5 t2 T' |( R, r7 b- U* Wos.tvboxnow.comThis crazy looking structure in Western Australia is called the Spider crater, for obvious reasons. Geologists determined it was
# C% t9 H4 ]3 i/ x; F6 u& \an impact crater when they found shatter cones, telltale cone-shaped, grooved rocks found only around impacts. The crazy * P$ g( e& L5 \4 t
looking legs surrounding the impact are mostly due to erosion of different rock layers. The harder sandstone ridges withstood 4 r8 J4 I( H' x& A; \4 L
the weathering of wind and water better than the softer intervening layers. The crater is somewhere between 600 million os.tvboxnow.com: _2 \4 w0 D5 H* }
and 900 million years old and the raised area at its center is around 1,600 feet wide.os.tvboxnow.com5 J9 Z0 A8 l2 [2 s' N" i8 l
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The image above is a false-color image taken by the Advanced Spaceborne Thermal Emission and Reflection Radiometer on tvb now,tvbnow,bttvb7 V8 ~4 s! q6 t+ v
NASA’s Terra. The true-color image below was captured by Taiwan’s Formost-2 satellite
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# m6 k8 `( g' n3 f! 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。
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The Gosses Bluff crater in Australia’s Northern Territory sits between two mountain ranges. The raised circular feature in the os.tvboxnow.com4 D# t# s  _6 `% u. J
center of the structure is around 2.8 miles across, but the original crater rim was probably at the edge of the surrounding   z5 n* @% m- C; Z8 i# `6 v9 y, J
grayish area. The crater was formed caused by an asteroid impact around 140 million years ago.$ j1 O' m. L, H6 r

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/ h* h! M( r: e* E5 ?1 ]8 l/ Q( J; otvb now,tvbnow,bttvbClearwater Lakes in Quebec, Canada were formed by a pair of asteroid impact craters. The impacts probably occurred
/ N7 p8 ?# I1 Q, ?( }8 e公仔箱論壇simultaneously around 290 million years ago. The larger crater measures 22 miles across.4 z( |; D( a& E$ b* N

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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 : ~% C& ?1 \/ ~. c8 V/ {
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" p' p+ x7 N, e+ P# s/ a7 U+ I
the space shuttle. Irregular surfaces show up brightly and smooth areas are dark. The white splotch at the bottom of the os.tvboxnow.com5 c6 h0 H8 s, |3 @+ H, b: ?' K
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
2 G1 x4 |; Y( ~7 v$ Aejected during the impact, the red is limestone outcrop and the green areas are mostly vegetation. The impact occurred os.tvboxnow.com$ V% T- O! @" A0 G( B  b- v7 ?
around 5 million years ago.
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! k) j0 h- @$ \+ @os.tvboxnow.comThe Lonar crater in Maharashta, India is around 6,000 feet wide and 500 feet deep and contains a saltwater lake.
, [/ N1 W2 p  O' h% g" Htvb now,tvbnow,bttvbScientists determined the structure was caused by an asteroid through clues such as the presence of maskelynite, tvb now,tvbnow,bttvb/ l, F9 ?8 z$ P* b% g. R: Q
a glass that is only formed by extremely high-velocity impacts. The impact occurred around 50,000 years ago.
; b& @  I* j) v5 @) @+ T6 dThis image was captured by the Advanced Spaceborne Thermal Emission and Reflection Radiometer on NASA’s os.tvboxnow.com( U9 b* N) i/ B/ M
Terra satellite. It is a simulated true-color imageTVBNOW 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 C0 E; S+ m) r8 `& _+ v
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The Vredefort Dome in South Africa is possibly the oldest and largest clearly visible asteroid impact on Earth.
. c) S/ |! E, n8 ZThe 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。& B; x' D# S- `2 u2 P3 Y  n5 {" \
Artist’s rendering of a space object or phenomenon, so we couldn’t resist this beauty. This is one man’s idea of what
5 s. `2 C) g  [; G* N1 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。a 300-mile wide asteroid would look impacting Earth. This event probably would have killed everything on the planet. os.tvboxnow.com3 l8 `4 j/ I% `) b& o$ n
Fortunately, NASA says nothing this big is headed our way anytime soon.