Asteroid Impact Craters on Earth as Seen From Space

, ^1 b. [2 H* R5.39.217.77:8898Asteroid impact craters are among the most interesting geological structures on any planet. Many other
8 ?* E) e4 p7 G/ |5.39.217.77:8898planets and moons in our solar system, including our own moon, are pock-marked with loads of craters.
% f6 Z; O0 c" p) o- RBut because Earth has a protective atmosphere and is geologically active — with plate tectonics and volcanic 5.39.217.77:8898' P* J7 s% K0 G7 P3 ^9 C6 L# A- z
eruptions, mostly relatively young oceanic crust, and harsh weathering from wind and water — impact
* a0 Z+ G7 G, d3 d& ~: C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. tvb now,tvbnow,bttvb. O9 u5 Q1 v! v+ J
One well-known example is our own Barringer crater, also known as Meteor Crater, in Arizona. The images here
0 E. @/ X2 o0 O+ Xtvb now,tvbnow,bttvbshow 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 公仔箱論壇% L, m7 R9 }4 k
in part to its location in the Sahara Desert in Chad. The 10 mile-wide crater is probably around 350 million 0 P+ I5 f" {+ m' s) G5 v  s8 ]
years old. The stripes are alternating rock ridges and sand layers, known as yardangs, caused by persistent tvb now,tvbnow,bttvb! K  w. \+ h/ [
unidirectional wind. The image above was taken by astronauts in the International Space Station in July. 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。7 Z$ ~. s# y! J
In 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,bttvb8 e/ d+ D3 x: F+ G3 n7 @2 ~
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* ]" d* k6 D+ X" Q公仔箱論壇The Shoemaker crater in Western Australia, formerly known as the Teague crater, was renamed in honor of the planetary tvb now,tvbnow,bttvb/ l7 B0 ^* j0 x/ ]) @2 G$ k! A
geologist Eugene Shoemaker for whom the Comet Shoemaker-Levy 9 is also named. The age of the crater unclear, but it
" j) }: B: }. R( Y2 d' N) Rcould be 1.7 billion years old, which makes it the oldest known impact in Australia. The brightly colored splotches are
seasonal salt-water lakes. This image was taken by the Landsat 7 satellite.

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The Manicouagan Crater in northern Canada is one of the largest impact craters known on Earth. The impact occurred
* S# F% g# l8 C3 Q4 R5.39.217.77:8898around 210 million years ago at the end of the Triassic period and may have caused a mass extinction that killed around 5.39.217.77:88981 `5 o: O3 f; F% j
60 percent of all species. Though the crater has mostly eroded, Lake Manicouagan outlines what is left of the 43-mile wide 公仔箱論壇6 p# O! r" b* H. I( e2 L
impact structure. The asteroid that created the crater is thought to have been about three miles wide. Today the lake is a
( r5 q+ J! F; c公仔箱論壇reservoir and popular salmon fishing location.
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This crazy looking structure in Western Australia is called the Spider crater, for obvious reasons. Geologists determined it was
an impact crater when they found shatter cones, telltale cone-shaped, grooved rocks found only around impacts. The crazy
) B8 n5 J+ l" L  `) z2 xlooking legs surrounding the impact are mostly due to erosion of different rock layers. The harder sandstone ridges withstood 0 s3 U$ N3 |' Y' v* y
the weathering of wind and water better than the softer intervening layers. The crater is somewhere between 600 million
  U, `$ r% [7 A, wand 900 million years old and the raised area at its center is around 1,600 feet wide.tvb now,tvbnow,bttvb( U* K8 @2 D  _) b" W' M

The image above is a false-color image taken by the Advanced Spaceborne Thermal Emission and Reflection Radiometer on 6 ?8 ~  z" _+ u# [7 @+ m  ]
NASA’s Terra. The true-color image below was captured by Taiwan’s Formost-2 satellite, f+ K( n( Y5 n0 n! a1 c
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/ ?* M' q' T) e4 M* }3 k: ]. FThe Gosses Bluff crater in Australia’s Northern Territory sits between two mountain ranges. The raised circular feature in the
) F& C# z$ i+ X* S公仔箱論壇center of the structure is around 2.8 miles across, but the original crater rim was probably at the edge of the surrounding 公仔箱論壇9 o! b% A- P2 W  z
grayish area. The crater was formed caused by an asteroid impact around 140 million years ago.
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2 @# o, f% D% [( w* b7 }  m1 o* }Clearwater Lakes in Quebec, Canada were formed by a pair of asteroid impact craters. The impacts probably occurred tvb now,tvbnow,bttvb  l0 p( L& F% m7 X
simultaneously around 290 million years ago. The larger crater measures 22 miles across.5.39.217.77:88988 B4 O+ F1 g6 ^: _+ F4 d1 f
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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 , m( {; M- Q! d# m; O' ]0 B
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公仔箱論壇' k1 y6 j7 \; d& g" m/ ]
the space shuttle. Irregular surfaces show up brightly and smooth areas are dark. The white splotch at the bottom of the
/ r$ e2 ]9 M( bphoto is a rocky hill, the darkest areas are wind-blown sand dunes, the blue around the crater’s rim may be material that was
1 C" M2 b, H, Mejected during the impact, the red is limestone outcrop and the green areas are mostly vegetation. The impact occurred
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.
; {3 g" m# |3 [; a公仔箱論壇Scientists determined the structure was caused by an asteroid through clues such as the presence of maskelynite,
# J& l" c  o0 s, V# I: j; b6 Ba glass that is only formed by extremely high-velocity impacts. The impact occurred around 50,000 years ago. 公仔箱論壇& j# y. T" D. x+ O0 W  p  E- P
This image was captured by the Advanced Spaceborne Thermal Emission and Reflection Radiometer on NASA’s 5.39.217.77:8898  O' I% }! T* f, k7 ?5 m3 N  O
Terra satellite. It is a simulated true-color image

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The Vredefort Dome in South Africa is possibly the oldest and largest clearly visible asteroid impact on Earth. tvb now,tvbnow,bttvb& l4 z$ o3 h0 {9 Z# O+ ]1 E
The 155-mile crater is approximately 60 miles southwest of Johannesburg and was formed around 2 billion years ago.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。+ W$ }. V% ?- s( p0 \: p

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/ `6 h% d8 K- J5 |- J( u公仔箱論壇Artist’s rendering of a space object or phenomenon, so we couldn’t resist this beauty. This is one man’s idea of what
% R4 N8 T. E; Q( R0 q, ?公仔箱論壇a 300-mile wide asteroid would look impacting Earth. This event probably would have killed everything on the planet. . s! E( a4 |) p% a. E) D% e
Fortunately, NASA says nothing this big is headed our way anytime soon.