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
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But because Earth has a protective atmosphere and is geologically active — with plate tectonics and volcanic ! M( i2 |6 H( e; d* J+ P2 A& x8 P  D
eruptions, mostly relatively young oceanic crust, and harsh weathering from wind and water — impact
* M4 v4 d; R# P! t: vstructures don’t last long and can be tough to come by.5.39.217.776 E& K" M# j) R  H! M$ B- T3 ?3 K

( R4 V$ i/ J) v" C* T) {# ?But on a few old pieces of continent, especially in arid deserts, the marks of asteroids have been preserved.   f. j9 r! V) c9 x5 s* W- g1 Q5 T
One well-known example is our own Barringer crater, also known as Meteor Crater, in Arizona. The images here
* V6 T' F( e0 B$ z. G8 u3 }show 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
4 s) W. Y1 F& B+ v2 t- {5.39.217.77in part to its location in the Sahara Desert in Chad. The 10 mile-wide crater is probably around 350 million
0 R6 s3 M( Y9 A' v$ C! e+ A5 X. Syears old. The stripes are alternating rock ridges and sand layers, known as yardangs, caused by persistent 公仔箱論壇: {% o! W9 c  |7 |
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。5 {' o0 e3 g! U) g, w' M" F
In 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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The Shoemaker crater in Western Australia, formerly known as the Teague crater, was renamed in honor of the planetary 5.39.217.773 b' n, j+ _: t7 \/ T
geologist Eugene Shoemaker for whom the Comet Shoemaker-Levy 9 is also named. The age of the crater unclear, but it 1 n( w9 w( t1 h/ X8 `9 o
could be 1.7 billion years old, which makes it the oldest known impact in Australia. The brightly colored splotches are
& K# `2 ]2 I! f0 Nseasonal salt-water lakes. This image was taken by the Landsat 7 satellite.
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$ l5 y2 y' x# P' @3 UThe Manicouagan Crater in northern Canada is one of the largest impact craters known on Earth. The impact occurred
- w) `1 i4 @  v& Ytvb now,tvbnow,bttvbaround 210 million years ago at the end of the Triassic period and may have caused a mass extinction that killed around
/ a% b. x) \( L6 d) j60 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; Z9 \5 w) ^& l7 j
impact structure. The asteroid that created the crater is thought to have been about three miles wide. Today the lake is a
2 X& U4 ~+ w2 \9 `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 8 @" _& s* L; Z* b# A. c& o
an impact crater when they found shatter cones, telltale cone-shaped, grooved rocks found only around impacts. The crazy % @* L0 t/ B8 Q: H9 K. `# c
looking legs surrounding the impact are mostly due to erosion of different rock layers. The harder sandstone ridges withstood # G6 T  S6 {) V
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 @% G& @: q* d% i+ f
and 900 million years old and the raised area at its center is around 1,600 feet wide.# K: H  R+ z1 o- A6 `
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The image above is a false-color image taken by the Advanced Spaceborne Thermal Emission and Reflection Radiometer on
( }- [' Z; |5 W0 A* A; W- q* jNASA’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
' q" o6 k: ?& d* d9 {5.39.217.77center of the structure is around 2.8 miles across, but the original crater rim was probably at the edge of the surrounding 5.39.217.77( [5 l8 z' w# k
grayish area. The crater was formed caused by an asteroid impact around 140 million years ago.
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. c% @$ y6 U% I  o公仔箱論壇Clearwater Lakes in Quebec, Canada were formed by a pair of asteroid impact craters. The impacts probably occurred
$ Z+ k  R( f  Bsimultaneously around 290 million years ago. The larger crater measures 22 miles across.公仔箱論壇0 j; A" A% b3 b( Z: q, @" Q: O

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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
1 v% ?( w7 q' ]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! i- M! e8 N2 P: [
the space shuttle. Irregular surfaces show up brightly and smooth areas are dark. The white splotch at the bottom of the
" S2 W2 Q1 U( u: Sphoto is a rocky hill, the darkest areas are wind-blown sand dunes, the blue around the crater’s rim may be material that was 公仔箱論壇1 T4 y% J" O0 q/ o: y6 U
ejected during the impact, the red is limestone outcrop and the green areas are mostly vegetation. The impact occurred
( R5 P0 M% m; B3 |  ]8 B- }# \公仔箱論壇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.
) ]# a6 G3 t" ?6 @tvb now,tvbnow,bttvbScientists determined the structure was caused by an asteroid through clues such as the presence of maskelynite, 公仔箱論壇3 W" F8 \$ G# ^3 q4 P% v, D! F+ F
a glass that is only formed by extremely high-velocity impacts. The impact occurred around 50,000 years ago.
4 R' u- N" Q7 d) gThis image was captured by the Advanced Spaceborne Thermal Emission and Reflection Radiometer on NASA’s
2 a$ D+ E! i4 |3 n6 V& ~* U/ q公仔箱論壇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.
$ Z( F! S) y$ J2 u/ S5 J& \' HThe 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 ) T" A0 Q5 z  ~1 p" F7 b
a 300-mile wide asteroid would look impacting Earth. This event probably would have killed everything on the planet. # b& V7 p2 h$ _5 w( e+ a
Fortunately, NASA says nothing this big is headed our way anytime soon.