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Asteroid impact craters are among the most interesting geological structures on any planet. Many other
: t3 k" s; _: J+ J/ R! f7 wtvb now,tvbnow,bttvbplanets and moons in our solar system, including our own moon, are pock-marked with loads of craters. tvb now,tvbnow,bttvb; H2 ^  e  {5 N
But because Earth has a protective atmosphere and is geologically active — with plate tectonics and volcanic
8 w! {5 B5 U% K) e* [eruptions, mostly relatively young oceanic crust, and harsh weathering from wind and water — impact
- a, e- A! q3 {8 bstructures don’t last long and can be tough to come by.
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3 V! P- U9 k4 v& w: v公仔箱論壇But on a few old pieces of continent, especially in arid deserts, the marks of asteroids have been preserved.
6 [# h' m, D3 r0 _# _6 M" B: ]tvb now,tvbnow,bttvbOne well-known example is our own Barringer crater, also known as Meteor Crater, in Arizona. The images here % p0 J' w# u8 y1 B
show some of the biggest, oldest and most interesting impact craters on the planet.- `5 c; ~* ]( e+ u' F# o9 a, ]( k: D+ j
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Aorounga crater, pictured above and below, is one of the best preserved impact craters on Earth, thanks tvb now,tvbnow,bttvb" c! i2 b8 L! ]6 F2 T
in part to its location in the Sahara Desert in Chad. The 10 mile-wide crater is probably around 350 million 公仔箱論壇- h4 M4 \; I/ o) |5 w* F8 M3 v0 O, y
years old. The stripes are alternating rock ridges and sand layers, known as yardangs, caused by persistent ! O+ s) c- C+ N9 V, T) r
unidirectional wind. The image above was taken by astronauts in the International Space Station in July.
7 s4 F* r# _2 Q- Q- k; l) zIn 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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The Shoemaker crater in Western Australia, formerly known as the Teague crater, was renamed in honor of the planetary * ]7 `+ Z/ }( p3 f8 x" C) p7 u+ l
geologist Eugene Shoemaker for whom the Comet Shoemaker-Levy 9 is also named. The age of the crater unclear, but it 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。  h3 K' v2 Z1 Z% C
could be 1.7 billion years old, which makes it the oldest known impact in Australia. The brightly colored splotches are
6 }+ H4 J0 s  c# J" v( d7 Yseasonal salt-water lakes. This image was taken by the Landsat 7 satellite.
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( O. D" x- j. Q$ @+ {% U1 OThe 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。" w4 x5 D! y2 {3 Z# v+ ^
around 210 million years ago at the end of the Triassic period and may have caused a mass extinction that killed around
5 n2 y* h. j6 [( a( _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。60 percent of all species. Though the crater has mostly eroded, Lake Manicouagan outlines what is left of the 43-mile wide
8 k: m* B, k3 K# |impact structure. The asteroid that created the crater is thought to have been about three miles wide. Today the lake is a
8 U: D: L" E/ D; f( e公仔箱論壇reservoir and popular salmon fishing location.8 Y4 m! M. O7 w- p

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0 U5 k+ ?* f, d" i8 t( [2 Ttvb 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。3 Q: s) P5 L1 N% P$ e2 {# Y+ B7 o

6 |4 I' U& q  E( n/ Z, EThis crazy looking structure in Western Australia is called the Spider crater, for obvious reasons. Geologists determined it was
) B# R+ b/ x: @8 z/ C! ]$ M公仔箱論壇an impact crater when they found shatter cones, telltale cone-shaped, grooved rocks found only around impacts. The crazy ' K. n% t* N! {0 Q. P+ v8 D
looking legs surrounding the impact are mostly due to erosion of different rock layers. The harder sandstone ridges withstood
0 H4 L: x. j8 K6 CTVBNOW 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 weathering of wind and water better than the softer intervening layers. The crater is somewhere between 600 million ! i" ?" c1 L4 F5 X
and 900 million years old and the raised area at its center is around 1,600 feet wide.0 }  ], B; @' X4 N  t; _- K
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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,bttvb& a  b. x$ H5 i; \7 [% z! i: N
NASA’s Terra. The true-color image below was captured by Taiwan’s Formost-2 satellitetvb now,tvbnow,bttvb% u/ R' i7 G$ Y& D) @0 Q
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The Gosses Bluff crater in Australia’s Northern Territory sits between two mountain ranges. The raised circular feature in the ' V8 t& k4 A: n, s& w/ `3 s- Y
center of the structure is around 2.8 miles across, but the original crater rim was probably at the edge of the surrounding
; T! D) }3 X- ?+ Y$ Mwww2.tvboxnow.comgrayish area. The crater was formed caused by an asteroid impact around 140 million years ago.tvb now,tvbnow,bttvb9 |# i; }6 y$ [3 q+ i4 X& T( x
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Clearwater Lakes in Quebec, Canada were formed by a pair of asteroid impact craters. The impacts probably occurred
( @( q- r2 q  Y9 P1 \tvb now,tvbnow,bttvbsimultaneously around 290 million years ago. The larger crater measures 22 miles across.公仔箱論壇6 ]' m/ B% u1 i
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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,bttvb4 C" Q$ [7 ^$ D$ u
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
/ M  \% T* n9 p1 j5 E: X 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. O+ }9 }; p* h! M
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
0 n5 L% ~0 O9 N# I9 xwww2.tvboxnow.comejected during the impact, the red is limestone outcrop and the green areas are mostly vegetation. The impact occurred
8 @0 i0 W2 q/ i# _4 s! `9 {around 5 million years ago.
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9 c  g7 s6 n$ P# k6 w8 K% p$ r2 v" JThe Lonar crater in Maharashta, India is around 6,000 feet wide and 500 feet deep and contains a saltwater lake. www2.tvboxnow.com" |/ i$ [, r0 X. W% B
Scientists determined the structure was caused by an asteroid through clues such as the presence of maskelynite,
, R  M( z' c" D9 M, P1 b- [公仔箱論壇a glass that is only formed by extremely high-velocity impacts. The impact occurred around 50,000 years ago.
% z: B! D3 j* I7 Ltvb now,tvbnow,bttvbThis image was captured by the Advanced Spaceborne Thermal Emission and Reflection Radiometer on NASA’s tvb now,tvbnow,bttvb! ^- V' P# f' u8 b
Terra satellite. It is a simulated true-color image" |3 j* N7 z7 ^) y3 d$ ^! t% k

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9 m; S6 A! r5 Q( A# SThe Vredefort Dome in South Africa is possibly the oldest and largest clearly visible asteroid impact on Earth.
$ j( b% L4 O4 ~$ q1 `8 R; |www2.tvboxnow.comThe 155-mile crater is approximately 60 miles southwest of Johannesburg and was formed around 2 billion years ago.公仔箱論壇$ \+ G6 j. H! W. ?+ @

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7 G0 \* K9 g" U6 }www2.tvboxnow.comArtist’s rendering of a space object or phenomenon, so we couldn’t resist this beauty. This is one man’s idea of what 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。  V( O$ Y* \1 ]1 i& I
a 300-mile wide asteroid would look impacting Earth. This event probably would have killed everything on the planet.
, U9 |# ?( ]; }% s1 L. q公仔箱論壇Fortunately, NASA says nothing this big is headed our way anytime soon.