1 d5 x; f  G: T" u5 o) \( L公仔箱論壇
' h- d- e4 ^% R7 `% l. J$ h/ OAsteroid impact craters are among the most interesting geological structures on any planet. Many other tvb now,tvbnow,bttvb" ^- ?: E2 n, |2 C! E  R
planets and moons in our solar system, including our own moon, are pock-marked with loads of craters.
/ c2 h/ F/ K* G9 q: ?But because Earth has a protective atmosphere and is geologically active — with plate tectonics and volcanic
9 }: ~0 T; q$ g* ^: q: \( yTVBNOW 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。eruptions, mostly relatively young oceanic crust, and harsh weathering from wind and water — impact
3 f- ~. L$ t6 P( qstructures don’t last long and can be tough to come by.4 u5 M3 J4 U, v4 ?' l5 m, |0 ?( N9 f
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。% I( P) ?( W! _% G
But on a few old pieces of continent, especially in arid deserts, the marks of asteroids have been preserved. ; @( x4 C# i8 Y
One well-known example is our own Barringer crater, also known as Meteor Crater, in Arizona. The images here   W' s+ d" o# K6 ?7 w. g; q
show some of the biggest, oldest and most interesting impact craters on the planet.
9 d8 m- n5 K1 O+ ]1 U% O6 U6 U+ 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。5.39.217.76/ m$ P* o# m3 ~+ G( M
Aorounga crater, pictured above and below, is one of the best preserved impact craters on Earth, thanks " c) @  K! d( R3 L! t# m
in part to its location in the Sahara Desert in Chad. The 10 mile-wide crater is probably around 350 million 9 W5 j9 g# n2 T3 {' u  i0 Y% `* A4 M
years old. The stripes are alternating rock ridges and sand layers, known as yardangs, caused by persistent
, S2 V" F$ h0 F$ v5.39.217.76unidirectional wind. The image above was taken by astronauts in the International Space Station in July. 5.39.217.76( a6 h8 Y; t6 g# @9 l4 u5 ?
In the radar image below, taken from the space shuttle in 1994, reveals that Aorounga may be one of two or three craters.5 l; p" a$ ~- e0 z# Q6 q9 }

- m, v9 x3 y* q6 H" O; N  hTVBNOW 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。5.39.217.768 m' q3 `7 g4 t
( K* E5 W: b2 {0 _" r- N
6 q/ _, l; t$ a8 `  u" ?! M' I2 B! k

5 [$ S0 {$ d0 O2 E) M# ~The Shoemaker crater in Western Australia, formerly known as the Teague crater, was renamed in honor of the planetary
( E' o4 T" R) x7 _! ~4 |9 Y1 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。geologist Eugene Shoemaker for whom the Comet Shoemaker-Levy 9 is also named. The age of the crater unclear, but it
# A8 m$ o' @% L2 p1 f) T5.39.217.76could be 1.7 billion years old, which makes it the oldest known impact in Australia. The brightly colored splotches are 5.39.217.769 A  h- r6 `2 d6 T3 G" }
seasonal salt-water lakes. This image was taken by the Landsat 7 satellite.tvb now,tvbnow,bttvb* i( \, [- A# W9 }7 |- M( `1 t  R4 J) i

6 F# N3 O  G, E8 C
/ }6 x- L' U; K1 z6 w  C5.39.217.76TVBNOW 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- P. \# M0 z4 t( H
The Manicouagan Crater in northern Canada is one of the largest impact craters known on Earth. The impact occurred 5.39.217.767 R' @2 a1 ?% a; F% ^8 z! c, W
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。! m% S5 y: s3 w* P5 _
60 percent of all species. Though the crater has mostly eroded, Lake Manicouagan outlines what is left of the 43-mile wide
! @( ~  W4 w( ]6 \# F4 U9 p" K公仔箱論壇impact structure. The asteroid that created the crater is thought to have been about three miles wide. Today the lake is a
! j2 e4 S2 [% i; a, H. A: Ktvb now,tvbnow,bttvbreservoir and popular salmon fishing location.
& J' W5 D8 H, J8 L% l7 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。) q& k, y0 B# J2 }' L

) {4 h) p* p& P4 M
8 i3 K. K: e+ p$ K1 ?5 f+ N
7 z* s+ \% e. G* ]! Itvb now,tvbnow,bttvb5.39.217.76* K+ c3 z; e. y  k
This crazy looking structure in Western Australia is called the Spider crater, for obvious reasons. Geologists determined it was
  X. f' K( h# b( vtvb now,tvbnow,bttvban impact crater when they found shatter cones, telltale cone-shaped, grooved rocks found only around impacts. The crazy 5.39.217.764 k3 R$ H0 O2 h& g+ N& V; M( A3 w0 ^* J6 k
looking legs surrounding the impact are mostly due to erosion of different rock layers. The harder sandstone ridges withstood
* t$ J. s' E+ \% D" N  Stvb now,tvbnow,bttvbthe weathering of wind and water better than the softer intervening layers. The crater is somewhere between 600 million
) I( F! S$ g0 E3 q5.39.217.76and 900 million years old and the raised area at its center is around 1,600 feet wide.5.39.217.76. q0 j, h" {" M5 O. W

  D$ y5 U0 V# U9 m7 n7 r$ S  P" ]/ M$ rtvb now,tvbnow,bttvbThe image above is a false-color image taken by the Advanced Spaceborne Thermal Emission and Reflection Radiometer on
$ A$ K' F6 j, G; @- W+ X公仔箱論壇NASA’s Terra. The true-color image below was captured by Taiwan’s Formost-2 satellite
, C/ Y/ g. I9 t+ W, ^2 |/ j5.39.217.76
, V' X" n; x8 v4 o4 V9 _. t, y+ s5.39.217.765.39.217.76" |; G- X2 g. D4 l

3 ?, j: s/ F/ y+ d' Y公仔箱論壇( L; m6 w$ d! h) W5 [
5.39.217.76- s5 z: j+ U( j7 c8 o, w
The Gosses Bluff crater in Australia’s Northern Territory sits between two mountain ranges. The raised circular feature in the 公仔箱論壇$ S' m# h% j' x6 X
center of the structure is around 2.8 miles across, but the original crater rim was probably at the edge of the surrounding
0 x7 `! p, W- vgrayish area. The crater was formed caused by an asteroid impact around 140 million years ago.tvb now,tvbnow,bttvb: @7 ]' {8 S+ H9 X
公仔箱論壇" i5 d% Q' j3 `( I, T8 ~

  q. {1 t6 u  B
6 g) R& D+ K3 w$ d- x+ ^5.39.217.76Clearwater Lakes in Quebec, Canada were formed by a pair of asteroid impact craters. The impacts probably occurred
0 _* s! \* ^! [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。simultaneously around 290 million years ago. The larger crater measures 22 miles across.
/ @2 Q. z4 @- c3 ]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。
, f6 k4 w! M- V5 C公仔箱論壇( H& D: g2 x7 q9 B, i
! A$ H& |3 U$ P2 \
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,bttvb6 I* t" k: t1 \: Y
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
/ ~! T4 [/ A& g& X/ k8 c4 r5.39.217.76 the space shuttle. Irregular surfaces show up brightly and smooth areas are dark. The white splotch at the bottom of the
; e+ ~; h( i; 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
  ?3 V0 ]  J  U7 L( Aejected during the impact, the red is limestone outcrop and the green areas are mostly vegetation. The impact occurred tvb now,tvbnow,bttvb' b* Q% y! d  m+ Z% z
around 5 million 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。9 A+ Z) J8 ?  x. F  W9 \
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。" I* d. h- {, H# m! h7 Y7 z4 m

- ?/ ~9 ^; p/ a5 Y公仔箱論壇公仔箱論壇$ p5 i5 {. D+ ?5 _0 ?+ b6 B
The Lonar crater in Maharashta, India is around 6,000 feet wide and 500 feet deep and contains a saltwater lake.
! R6 U0 K" a( S0 v1 _1 lScientists determined the structure was caused by an asteroid through clues such as the presence of maskelynite, 5.39.217.761 k' U0 L$ P% t
a glass that is only formed by extremely high-velocity impacts. The impact occurred around 50,000 years ago. : v5 K: s0 t2 R4 a3 o- X
This image was captured by the Advanced Spaceborne Thermal Emission and Reflection Radiometer on NASA’s 公仔箱論壇5 X2 M* u% T/ A- C$ C$ A. @/ f
Terra satellite. It is a simulated true-color image公仔箱論壇2 ^' B! K* r* A3 P& Z
5 P+ h- o# t7 F

* c1 c; M$ P* U' C2 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。0 c" O3 M8 _9 ]- d8 e
The Vredefort Dome in South Africa is possibly the oldest and largest clearly visible asteroid impact on Earth.
& b& [" B  ~9 D  Z. U5.39.217.76The 155-mile crater is approximately 60 miles southwest of Johannesburg and was formed around 2 billion years ago.
) J0 h+ c/ |) y9 c. _$ e  x- `$ 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。
3 d9 v& _$ r4 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。
: j+ v, h) s* D5.39.217.76
+ X1 Z( l  U; R! m/ L* r公仔箱論壇tvb now,tvbnow,bttvb) \: {# b6 Q4 ]' C# s$ ?$ y) t

" v" W" B/ m8 LTVBNOW 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。Artist’s rendering of a space object or phenomenon, so we couldn’t resist this beauty. This is one man’s idea of what 5.39.217.76/ A# P- Z. Q) }. }2 @* ]( Z  `
a 300-mile wide asteroid would look impacting Earth. This event probably would have killed everything on the planet.
4 n# h+ N+ z6 C- E, Q% z- b公仔箱論壇Fortunately, NASA says nothing this big is headed our way anytime soon.