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Asteroid impact craters are among the most interesting geological structures on any planet. Many other / n$ i; n4 v6 g1 n3 ~$ B
planets and moons in our solar system, including our own moon, are pock-marked with loads of craters. . f+ _& e d/ Q4 c% F! R
But because Earth has a protective atmosphere and is geologically active — with plate tectonics and volcanic , i* c; S1 p! |# W/ k
eruptions, mostly relatively young oceanic crust, and harsh weathering from wind and water — impact
" h# ~ |5 r1 U+ M) T4 ^5.39.217.77structures don’t last long and can be tough to come by.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。; f4 P$ N6 _) s* g
% X U! v$ w7 {5.39.217.77But on a few old pieces of continent, especially in arid deserts, the marks of asteroids have been preserved. tvb now,tvbnow,bttvb' b* S, f1 F. o D3 n
One well-known example is our own Barringer crater, also known as Meteor Crater, in Arizona. The images here
! |# n+ _" y5 L: Ktvb now,tvbnow,bttvbshow some of the biggest, oldest and most interesting impact craters on the planet.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。* l5 d, H4 v# c4 I
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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。 X, T+ K4 o0 f
in part to its location in the Sahara Desert in Chad. The 10 mile-wide crater is probably around 350 million # Q# l9 i$ `5 b/ W" {
years old. The stripes are alternating rock ridges and sand layers, known as yardangs, caused by persistent
2 l3 X+ d2 y7 X: K- h公仔箱論壇unidirectional wind. The image above was taken by astronauts in the International Space Station in July. 5.39.217.77% N# J! D9 \; s& R# T
In the radar image below, taken from the space shuttle in 1994, reveals that Aorounga may be one of two or three craters., `# _. e; I2 D5 ?! h: ~5 @3 V
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* I# j3 s& v$ A& S( _& jTVBNOW 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 Shoemaker crater in Western Australia, formerly known as the Teague crater, was renamed in honor of the planetary # q: ^$ z+ K8 M
geologist Eugene Shoemaker for whom the Comet Shoemaker-Levy 9 is also named. The age of the crater unclear, but it 2 Z, x5 y2 @9 N/ c/ X. K
could be 1.7 billion years old, which makes it the oldest known impact in Australia. The brightly colored splotches are
- A# w' g) n6 y S H% FTVBNOW 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。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 2 C4 G X. J: p5 |: s+ P
around 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。: W5 a6 `/ S6 _* n$ ]/ a4 {
60 percent of all species. Though the crater has mostly eroded, Lake Manicouagan outlines what is left of the 43-mile wide
9 X, o; w; P" Q$ M* Yimpact structure. The asteroid that created the crater is thought to have been about three miles wide. Today the lake is a
5 D6 u+ {! N% { p( ereservoir and popular salmon fishing location.& W, a/ k4 P5 B* h) }
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( I# o( Z* n9 j: v8 d公仔箱論壇 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。) Z8 q% d) \" Z; n+ I0 {
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。9 n) e! ?( T& a# z8 W/ l4 R k
This crazy looking structure in Western Australia is called the Spider crater, for obvious reasons. Geologists determined it was tvb now,tvbnow,bttvb' i) a9 r5 n$ s! m/ k: I' j
an impact crater when they found shatter cones, telltale cone-shaped, grooved rocks found only around impacts. The crazy
3 [* F$ B+ [ C) z+ | qlooking legs surrounding the impact are mostly due to erosion of different rock layers. The harder sandstone ridges withstood tvb now,tvbnow,bttvb! w2 @) N& `+ R; t( P! T8 n" ]& C
the weathering of wind and water better than the softer intervening layers. The crater is somewhere between 600 million 公仔箱論壇6 v1 @; I; ~7 \. X0 P3 J. z. d8 u
and 900 million years old and the raised area at its center is around 1,600 feet wide.tvb now,tvbnow,bttvb7 U- ]* x# x5 i, Y7 n
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The image above is a false-color image taken by the Advanced Spaceborne Thermal Emission and Reflection Radiometer on 公仔箱論壇& x; j o A0 _
NASA’s Terra. The true-color image below was captured by Taiwan’s Formost-2 satellite5.39.217.77+ ^% R6 R/ H. ?8 A8 Y/ {' e' r
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The Gosses Bluff crater in Australia’s Northern Territory sits between two mountain ranges. The raised circular feature in the
( |5 Y" J+ I8 h; N1 j. i% l0 O5.39.217.77center of the structure is around 2.8 miles across, but the original crater rim was probably at the edge of the surrounding 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。/ h8 M* V3 j0 i9 F% z
grayish area. The crater was formed caused by an asteroid impact around 140 million years ago.tvb now,tvbnow,bttvb. c' c. D. A9 ?0 u6 s% V
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" `5 @+ K L& {. ] PClearwater Lakes in Quebec, Canada were formed by a pair of asteroid impact craters. The impacts probably occurred
- c& v x' G# V+ h8 w, \( J5.39.217.77simultaneously around 290 million years ago. The larger crater measures 22 miles across.
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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,bttvb' f) K& X \0 [5 @% V1 F6 n% M7 P
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
/ x& U6 |3 d! j( W! y0 {: p" x" J the space shuttle. Irregular surfaces show up brightly and smooth areas are dark. The white splotch at the bottom of the
2 u' k: Q+ x: L- N+ O7 d5.39.217.77photo is a rocky hill, the darkest areas are wind-blown sand dunes, the blue around the crater’s rim may be material that was 3 ~2 T! k* `/ ?: [
ejected during the impact, the red is limestone outcrop and the green areas are mostly vegetation. The impact occurred
6 U c; ^5 b+ L1 e- }, m. rTVBNOW 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。around 5 million years ago.3 `, b+ J7 ]3 e
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/ C# H( J9 L/ d3 X9 [7 X5 @& CThe Lonar crater in Maharashta, India is around 6,000 feet wide and 500 feet deep and contains a saltwater lake. tvb now,tvbnow,bttvb2 F, T% l# T/ h2 `! N
Scientists determined the structure was caused by an asteroid through clues such as the presence of maskelynite,
1 y3 g3 T$ R) ~/ m3 }a glass that is only formed by extremely high-velocity impacts. The impact occurred around 50,000 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。4 Q3 `+ P1 Q! d6 y
This image was captured by the Advanced Spaceborne Thermal Emission and Reflection Radiometer on NASA’s
6 _" Y) I; l+ q. X0 K" u }公仔箱論壇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。/ ?$ f* @+ p/ t: A% V8 ]
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The Vredefort Dome in South Africa is possibly the oldest and largest clearly visible asteroid impact on Earth. / y( C' a. W: C! v
The 155-mile crater is approximately 60 miles southwest of Johannesburg and was formed around 2 billion years ago.
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$ D0 w- o: V. o$ ~5.39.217.77Artist’s rendering of a space object or phenomenon, so we couldn’t resist this beauty. This is one man’s idea of what
8 L- i/ [6 ~6 ?9 q4 L" l0 X5.39.217.77a 300-mile wide asteroid would look impacting Earth. This event probably would have killed everything on the planet. & L5 R M! Q; Y+ ?- V9 F4 i" d
Fortunately, NASA says nothing this big is headed our way anytime soon.
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