2 t, D0 D+ G3 x$ L4 p$ OTVBNOW 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. u0 f5 m7 R5 Y2 f& `. O$ l3 _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。Asteroid impact craters are among the most interesting geological structures on any planet. Many other tvb now,tvbnow,bttvb9 e$ G" a) P$ Y: p
planets and moons in our solar system, including our own moon, are pock-marked with loads of craters.
+ H: S+ ]8 h  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。But because Earth has a protective atmosphere and is geologically active — with plate tectonics and volcanic 公仔箱論壇6 L: ^+ m5 h- i' X3 ^; ?
eruptions, mostly relatively young oceanic crust, and harsh weathering from wind and water — impact
- B+ D8 y; H, T' T, |- u. rstructures 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. 5.39.217.77:8898# L! ?  a/ a3 t. l
One well-known example is our own Barringer crater, also known as Meteor Crater, in Arizona. The images here 公仔箱論壇( W; q0 @; |3 [; J# o7 ]
show some of the biggest, oldest and most interesting impact craters on the planet.
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2 C9 t* S* x2 S" y公仔箱論壇Aorounga crater, pictured above and below, is one of the best preserved impact craters on Earth, thanks ( b: K3 {1 C( N, x/ u, F2 \
in part to its location in the Sahara Desert in Chad. The 10 mile-wide crater is probably around 350 million ) e2 X7 O3 q& w! a& o. j4 N9 z
years old. The stripes are alternating rock ridges and sand layers, known as yardangs, caused by persistent 公仔箱論壇5 \4 B2 D/ R& j5 l( o, C1 }' {: Z
unidirectional wind. The image above was taken by astronauts in the International Space Station in July. 公仔箱論壇' p/ E* _" p* G/ h. C4 I* I. d
In the radar image below, taken from the space shuttle in 1994, reveals that Aorounga may be one of two or three craters.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 q, t& x6 ^8 }& c0 {) q8 X

+ _1 h, T4 i0 ]$ [tvb now,tvbnow,bttvb: r% O6 p- ?! ^7 C

% l, x7 \' c* N2 P! H7 I5.39.217.77:8898TVBNOW 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。6 d. S1 V9 R( @6 G5 |

) [- ^( \( a! y% D& p4 B6 |: |The Shoemaker crater in Western Australia, formerly known as the Teague crater, was renamed in honor of the planetary
+ I  R; S# N4 v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 # g3 H5 O0 U: H+ a9 R9 `
could be 1.7 billion years old, which makes it the oldest known impact in Australia. The brightly colored splotches are " @, Y7 [! R3 z- A' t2 c1 J
seasonal salt-water lakes. This image was taken by the Landsat 7 satellite.1 [$ ~$ h5 d( V% j' Z& R$ ^

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The Manicouagan Crater in northern Canada is one of the largest impact craters known on Earth. The impact occurred
+ Y4 ?; i9 [# \# U/ J  W  n5.39.217.77:8898around 210 million years ago at the end of the Triassic period and may have caused a mass extinction that killed around 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。# ~: D/ u; T* [( _7 j6 q5 K/ G/ j
60 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! \; [# T3 J5 r. h
impact structure. The asteroid that created the crater is thought to have been about three miles wide. Today the lake is a 5.39.217.77:8898( }; v9 c7 w* B6 f" a" \6 X
reservoir and popular salmon fishing location.公仔箱論壇; A4 o! @1 B% p- O) s- ]

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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1 u5 U, W! ^0 ]+ ~
an impact crater when they found shatter cones, telltale cone-shaped, grooved rocks found only around impacts. The crazy
/ K! k! X& m; m: g* R公仔箱論壇looking legs surrounding the impact are mostly due to erosion of different rock layers. The harder sandstone ridges withstood 5.39.217.77:8898: a+ y" e, A$ Z! }" b( G7 C
the weathering of wind and water better than the softer intervening layers. The crater is somewhere between 600 million
4 o* w1 R0 _! @- _6 o0 mand 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
  |1 [7 ~" D4 c9 @/ n) J/ D: mTVBNOW 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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/ D8 U0 K# w# m( Y; L9 L公仔箱論壇The Gosses Bluff crater in Australia’s Northern Territory sits between two mountain ranges. The raised circular feature in the tvb now,tvbnow,bttvb1 Z# ^$ f- _5 g
center of the structure is around 2.8 miles across, but the original crater rim was probably at the edge of the surrounding
5 {& Y5 ]/ q$ k1 vtvb now,tvbnow,bttvbgrayish area. The crater was formed caused by an asteroid impact around 140 million years ago.
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1 ]6 f) B; j9 G3 \5.39.217.77:8898Clearwater Lakes in Quebec, Canada were formed by a pair of asteroid impact craters. The impacts probably occurred ; U, z' W. L. O1 d. l: q
simultaneously around 290 million years ago. The larger crater measures 22 miles across.5.39.217.77:88980 H6 [& Y0 k5 x

8 }$ H+ V! p& c# h% [5 N# }" O0 bTVBNOW 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。5.39.217.77:8898" T& p' J4 S4 Z! @

! P' `, R2 e+ [! XThe Roter Kamm crater in Namibia is hard to see in visible light, but shows up more clearly with imaging radar. The crater’s & `, l5 E5 J& j' i
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
: ^# B. Q4 E; Ftvb now,tvbnow,bttvb the space shuttle. Irregular surfaces show up brightly and smooth areas are dark. The white splotch at the bottom of the
  f5 q# p+ T+ 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。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 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 B1 N; H1 m. V2 `
ejected during the impact, the red is limestone outcrop and the green areas are mostly vegetation. The impact occurred 公仔箱論壇; g- B- o7 k7 s2 I. e
around 5 million years ago.
$ @. b* d1 F. U6 }6 P6 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。: V  w( q6 v  ~) u9 v" \

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: e& Q+ k4 G! d8 ]# Q) O* ZTVBNOW 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 Lonar crater in Maharashta, India is around 6,000 feet wide and 500 feet deep and contains a saltwater lake.
5 k  A3 r; D* T3 z/ v& _( U9 rScientists determined the structure was caused by an asteroid through clues such as the presence of maskelynite, 4 c" m0 K+ n) @$ p' X0 G
a glass that is only formed by extremely high-velocity impacts. The impact occurred around 50,000 years ago. 1 K& C# {7 {+ U3 i! i
This image was captured by the Advanced Spaceborne Thermal Emission and Reflection Radiometer on NASA’s
& {0 ?: T% {" Ntvb now,tvbnow,bttvbTerra satellite. It is a simulated true-color image
+ s, g5 J! _# z) `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。
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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。! o7 ]( P3 y% U, Z/ f; p
The Vredefort Dome in South Africa is possibly the oldest and largest clearly visible asteroid impact on Earth. . w# @- H4 A: O) S
The 155-mile crater is approximately 60 miles southwest of Johannesburg and was formed around 2 billion years ago.1 Y- I- b3 }5 u! T4 g2 y8 z

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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 tvb now,tvbnow,bttvb; }9 ~" K+ M& f! U) f
a 300-mile wide asteroid would look impacting Earth. This event probably would have killed everything on the planet.
) n% s5 i2 O3 ZTVBNOW 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.