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Asteroid impact craters are among the most interesting geological structures on any planet. Many other
5 v3 ~3 r* [. f) u/ L6 v- Y+ |- @公仔箱論壇planets and moons in our solar system, including our own moon, are pock-marked with loads of craters.
1 W q6 C8 V: u- y8 ftvb now,tvbnow,bttvbBut because Earth has a protective atmosphere and is geologically active — with plate tectonics and volcanic 9 {3 a0 ]1 O3 P6 O( q# r, n- H' U
eruptions, mostly relatively young oceanic crust, and harsh weathering from wind and water — impact
/ S; w9 O0 v: Y7 P: 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。structures don’t last long and can be tough to come by.5.39.217.77:88981 ~- B& Q0 @/ X( I- X
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But on a few old pieces of continent, especially in arid deserts, the marks of asteroids have been preserved.
' U6 T( [/ v! Z: R8 w5 k# U+ _One well-known example is our own Barringer crater, also known as Meteor Crater, in Arizona. The images here
( D4 I/ f% s$ @$ h. J; G; Jshow some of the biggest, oldest and most interesting impact craters on the planet.
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) S% |. \% f- U% K5.39.217.77:8898Aorounga 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。8 x4 N' d7 D& u, ]1 Y7 \
in part to its location in the Sahara Desert in Chad. The 10 mile-wide crater is probably around 350 million " |& @6 Q* k) S# p" l
years old. The stripes are alternating rock ridges and sand layers, known as yardangs, caused by persistent
* [8 o9 Y" a" ]8 p# g1 U) }tvb now,tvbnow,bttvbunidirectional wind. The image above was taken by astronauts in the International Space Station in July.
$ N, P" M/ G3 L- y% {- x2 o- w5 i公仔箱論壇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。' `' w" d, M0 _
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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。- D5 S/ l$ h" D9 K7 {8 P) {+ S) h
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The Shoemaker crater in Western Australia, formerly known as the Teague crater, was renamed in honor of the planetary 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。; p+ J4 g: o+ o
geologist Eugene Shoemaker for whom the Comet Shoemaker-Levy 9 is also named. The age of the crater unclear, but it ; Y, A8 d( U* P4 W* ^& m& }: ~
could be 1.7 billion years old, which makes it the oldest known impact in Australia. The brightly colored splotches are
) s5 @6 T/ S1 J: P+ ]3 W& r- yseasonal 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 " {! }7 x- V# c, @
around 210 million years ago at the end of the Triassic period and may have caused a mass extinction that killed around 公仔箱論壇# ~. E n. i, O' z- S
60 percent of all species. Though the crater has mostly eroded, Lake Manicouagan outlines what is left of the 43-mile wide ! }9 p0 |4 V( H; p, x
impact structure. The asteroid that created the crater is thought to have been about three miles wide. Today the lake is a
3 C# a6 H4 |! Ereservoir 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 5.39.217.77:8898* L+ u$ e% B- C
an impact crater when they found shatter cones, telltale cone-shaped, grooved rocks found only around impacts. The crazy , q" `: k$ h6 g q- I
looking legs surrounding the impact are mostly due to erosion of different rock layers. The harder sandstone ridges withstood 1 u9 @6 F& z7 Y
the weathering of wind and water better than the softer intervening layers. The crater is somewhere between 600 million
4 x( {8 q, ?7 E1 d' |& F/ q" ?5 [and 900 million years old and the raised area at its center is around 1,600 feet wide.
# q& h7 \" u- Y7 e7 s* Q8 N. etvb 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。# A: b) ]( Z! z( _6 A0 r: W* T
The image above is a false-color image taken by the Advanced Spaceborne Thermal Emission and Reflection Radiometer on 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。, ?0 u( ~( ~. z
NASA’s Terra. The true-color image below was captured by Taiwan’s Formost-2 satellite
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' b: ?4 v, Q/ tTVBNOW 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 Gosses Bluff crater in Australia’s Northern Territory sits between two mountain ranges. The raised circular feature in the
: X1 a# P+ [% ~" a0 q1 B4 Rcenter of the structure is around 2.8 miles across, but the original crater rim was probably at the edge of the surrounding 5.39.217.77:8898/ J. a6 N& I7 V# ?; s2 ~
grayish area. The crater was formed caused by an asteroid impact around 140 million years ago.公仔箱論壇) h* @6 @! k! o0 B
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Clearwater Lakes in Quebec, Canada were formed by a pair of asteroid impact craters. The impacts probably occurred
6 z! s: C4 ]- @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。1 C; {$ {2 {& n
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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- B( T) @! B/ V) {
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 boardtvb now,tvbnow,bttvb0 s r2 @ }( O4 O0 w# t. X1 e3 r3 C5 l
the space shuttle. Irregular surfaces show up brightly and smooth areas are dark. The white splotch at the bottom of the
9 C; Q+ z* I8 `* O% o2 ]/ _$ B aphoto is a rocky hill, the darkest areas are wind-blown sand dunes, the blue around the crater’s rim may be material that was ' V! S0 y2 E, ?" F$ ]- x
ejected during the impact, the red is limestone outcrop and the green areas are mostly vegetation. The impact occurred ' \# \1 V3 U! | y- V
around 5 million years ago.
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! r' n- f! F, \; z T9 ktvb now,tvbnow,bttvbThe Lonar crater in Maharashta, India is around 6,000 feet wide and 500 feet deep and contains a saltwater lake.
" Y8 ~' Z3 d5 B6 C) EScientists determined the structure was caused by an asteroid through clues such as the presence of maskelynite, 0 I# E1 i# D e% G) q7 m
a glass that is only formed by extremely high-velocity impacts. The impact occurred around 50,000 years ago. 5.39.217.77:8898" t/ U/ p3 w0 j4 C& A+ q" Y
This image was captured by the Advanced Spaceborne Thermal Emission and Reflection Radiometer on NASA’s
5 O2 x( j% Q6 l0 E# O H7 N4 nTerra 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.
8 m* A6 ? S) n/ Dtvb now,tvbnow,bttvbThe 155-mile crater is approximately 60 miles southwest of Johannesburg and was formed around 2 billion years ago.
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) B2 u3 `" e% }2 i+ a! m2 w$ Ktvb 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。$ I9 D9 c5 I8 X8 ^0 z5 S! d
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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,bttvb0 [6 C/ E4 l H: Z2 j* I/ }- r: B
a 300-mile wide asteroid would look impacting Earth. This event probably would have killed everything on the planet.
) h$ F- s' R, K y; H( @/ stvb now,tvbnow,bttvbFortunately, NASA says nothing this big is headed our way anytime soon.
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