Asteroid Impact Craters on Earth as Seen From Space

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Asteroid impact craters are among the most interesting geological structures on any planet. Many other 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) G- Z% m- y4 f% a( J& ]
planets and moons in our solar system, including our own moon, are pock-marked with loads of 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。. M+ t# l; K: z8 a" E" M
But because Earth has a protective atmosphere and is geologically active — with plate tectonics and volcanic
eruptions, mostly relatively young oceanic crust, and harsh weathering from wind and water — impact 5 q5 L# s! z7 {+ {- J- q, Y# G& T
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.
One well-known example is our own Barringer crater, also known as Meteor Crater, in Arizona. The images here
: b( z  @$ u: H8 r* F+ A3 Hshow 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 9 F; z8 H  k# w3 c- y8 z
in part to its location in the Sahara Desert in Chad. The 10 mile-wide crater is probably around 350 million
- u0 K3 y) m7 `# z) w& c) iyears old. The stripes are alternating rock ridges and sand layers, known as yardangs, caused by persistent
( l. O% |* v! {; T0 T- {. W1 Nunidirectional wind. The image above was taken by astronauts in the International Space Station in July.
- k/ z8 `) m, K8 aIn 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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1 Y# j- E; Z1 j5 `" L公仔箱論壇The Shoemaker crater in Western Australia, formerly known as the Teague crater, was renamed in honor of the planetary : N5 I2 s: h3 L. c% o7 L" L% r2 g+ K  s* ]
geologist Eugene Shoemaker for whom the Comet Shoemaker-Levy 9 is also named. The age of the crater unclear, but it
1 ?: m: \, @, ~( A  jcould be 1.7 billion years old, which makes it the oldest known impact in Australia. The brightly colored splotches are 5.39.217.76- o7 Q0 ^2 K1 l; Z% {* Q
seasonal salt-water lakes. This image was taken by the Landsat 7 satellite.% i8 {: R7 f& f' ~/ x2 z  g

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The Manicouagan Crater in northern Canada is one of the largest impact craters known on Earth. The impact occurred 公仔箱論壇) u" f- }, N' Y8 e4 V
around 210 million years ago at the end of the Triassic period and may have caused a mass extinction that killed around , r* Q7 F6 {$ w# d/ ]+ ~  [4 l7 Y8 c$ C
60 percent of all species. Though the crater has mostly eroded, Lake Manicouagan outlines what is left of the 43-mile wide 5.39.217.76( r- g: E4 l) k1 w! P- t
impact structure. The asteroid that created the crater is thought to have been about three miles wide. Today the lake is a
! P6 m7 f- A) T公仔箱論壇reservoir and popular salmon fishing location.公仔箱論壇$ ]0 g* v$ g* E8 q! k
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/ j' \- c. ^: V/ I6 p" }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 tvb now,tvbnow,bttvb; h. F0 p9 F9 x  F" n, s0 c
looking legs surrounding the impact are mostly due to erosion of different rock layers. The harder sandstone ridges withstood : M% V* X9 G3 l2 c! C, P7 d0 o
the weathering of wind and water better than the softer intervening layers. The crater is somewhere between 600 million
, L# k3 s$ B. e3 t/ Z) Cand 900 million years old and the raised area at its center is around 1,600 feet wide.

The image above is a false-color image taken by the Advanced Spaceborne Thermal Emission and Reflection Radiometer on tvb now,tvbnow,bttvb1 S* s: Z! k" S3 I2 ]. c' ]
NASA’s Terra. The true-color image below was captured by Taiwan’s Formost-2 satellite
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The Gosses Bluff crater in Australia’s Northern Territory sits between two mountain ranges. The raised circular feature in the
0 c/ k3 O* h: [# mtvb now,tvbnow,bttvbcenter of the structure is around 2.8 miles across, but the original crater rim was probably at the edge of the surrounding & s, y) |0 f! f  P# k& [
grayish area. The crater was formed caused by an asteroid impact around 140 million years ago.
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0 b# K$ h' r; P1 T, X5.39.217.76Clearwater Lakes in Quebec, Canada were formed by a pair of asteroid impact craters. The impacts probably occurred
( g. M1 Q' W7 c5 y公仔箱論壇simultaneously around 290 million years ago. The larger crater measures 22 miles across.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。; {' }- T( R0 _
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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 , g  D- s7 W) G1 e7 V' C& O) L
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
6 @6 v" T9 w; [) f5.39.217.76 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* q! C7 X, y8 H
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。7 C; T/ h0 Y6 b1 J3 B
ejected 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.
Scientists determined the structure was caused by an asteroid through clues such as the presence of maskelynite,
; F2 ?) F. e- B5 P$ v公仔箱論壇a glass that is only formed by extremely high-velocity impacts. The impact occurred around 50,000 years ago.
This image was captured by the Advanced Spaceborne Thermal Emission and Reflection Radiometer on NASA’s
Terra satellite. It is a simulated true-color image
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& c* g$ v% n8 N: p! p7 p& MThe Vredefort Dome in South Africa is possibly the oldest and largest clearly visible asteroid impact on Earth. 公仔箱論壇1 ~& s% o+ i; G2 T! x0 u% u2 u* U4 C! ^
The 155-mile crater is approximately 60 miles southwest of Johannesburg and was formed around 2 billion years ago.
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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
% z. k; B- T0 R* i1 X$ qa 300-mile wide asteroid would look impacting Earth. This event probably would have killed everything on the planet. 公仔箱論壇+ k4 S9 a/ @1 J
Fortunately, NASA says nothing this big is headed our way anytime soon.