Asteroid Impact Craters on Earth as Seen From Space

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' y& ?1 V3 T2 o* t公仔箱論壇Asteroid impact craters are among the most interesting geological structures on any planet. Many other
& g8 c; l" I( M& k+ K5 ]% Iplanets and moons in our solar system, including our own moon, are pock-marked with loads of craters. tvb now,tvbnow,bttvb4 G3 l; u. o  f) u
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
/ p- t  S2 L+ l7 Y  t  Hstructures 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. www2.tvboxnow.com% y6 ~( w! j# O% d& {# I
One well-known example is our own Barringer crater, also known as Meteor Crater, in Arizona. The images here
) M0 X) Q" Q3 F2 G  sshow 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。7 e, J" C2 [6 `  S, b

Aorounga crater, pictured above and below, is one of the best preserved impact craters on Earth, thanks
) H/ n9 `$ |! h公仔箱論壇in part to its location in the Sahara Desert in Chad. The 10 mile-wide crater is probably around 350 million
years old. The stripes are alternating rock ridges and sand layers, known as yardangs, caused by persistent 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。" u1 S& o7 x' d$ a$ v
unidirectional wind. The image above was taken by astronauts in the International Space Station in July.
: w2 C+ }: S- C- [/ ]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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8 J: }4 v6 X  a& sThe Shoemaker crater in Western Australia, formerly known as the Teague crater, was renamed in honor of the planetary - b- g7 d# ]. J! d- ]: T
geologist Eugene Shoemaker for whom the Comet Shoemaker-Levy 9 is also named. The age of the crater unclear, but it
- t9 D/ W5 j9 d& K# Scould be 1.7 billion years old, which makes it the oldest known impact in Australia. The brightly colored splotches are
seasonal salt-water lakes. This image was taken by the Landsat 7 satellite.tvb now,tvbnow,bttvb% P' ~$ B& Q/ [: A8 ?0 s

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The Manicouagan Crater in northern Canada is one of the largest impact craters known on Earth. The impact occurred tvb now,tvbnow,bttvb3 ~( L+ a3 B; F0 }/ l9 {, f8 y/ F4 G
around 210 million years ago at the end of the Triassic period and may have caused a mass extinction that killed around
- }, M) u( X- }8 X" d5 A. X60 percent of all species. Though the crater has mostly eroded, Lake Manicouagan outlines what is left of the 43-mile wide
* t8 Y3 p- C6 C0 wimpact structure. The asteroid that created the crater is thought to have been about three miles wide. Today the lake is a
& W# D# `% h8 j4 vreservoir and popular salmon fishing location.
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2 j/ b/ ~: _0 g! Z公仔箱論壇This crazy looking structure in Western Australia is called the Spider crater, for obvious reasons. Geologists determined it was 5 Q7 _% ?2 }. b
an impact crater when they found shatter cones, telltale cone-shaped, grooved rocks found only around impacts. The crazy
looking legs surrounding the impact are mostly due to erosion of different rock layers. The harder sandstone ridges withstood ' O' V- z4 `0 t6 y9 ]5 @' G; O7 R
the weathering of wind and water better than the softer intervening layers. The crater is somewhere between 600 million 公仔箱論壇+ B& |# e; E! O: l
and 900 million years old and the raised area at its center is around 1,600 feet wide., w! w' W" D4 D& q! T
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The image above is a false-color image taken by the Advanced Spaceborne Thermal Emission and Reflection Radiometer on tvb now,tvbnow,bttvb3 }" h8 G; i9 G7 ?
NASA’s Terra. The true-color image below was captured by Taiwan’s Formost-2 satellitewww2.tvboxnow.com/ t& ]. k4 M# P2 Q$ ]: Q7 O

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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8 E( z) [0 D# d- T6 @
center of the structure is around 2.8 miles across, but the original crater rim was probably at the edge of the surrounding
. }- H/ ^. {# Agrayish area. The crater was formed caused by an asteroid impact around 140 million years ago.
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Clearwater Lakes in Quebec, Canada were formed by a pair of asteroid impact craters. The impacts probably occurred
) r0 m. y; n! j6 l1 e( Ssimultaneously around 290 million years ago. The larger crater measures 22 miles across.) o. _) H% ?1 l: }0 v

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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 www2.tvboxnow.com! k0 o6 Q% `+ d& {
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公仔箱論壇2 W8 K. e0 |% D$ F5 B8 j2 n  \
the space shuttle. Irregular surfaces show up brightly and smooth areas are dark. The white splotch at the bottom of the www2.tvboxnow.com  Y, A- Z6 `; d; K4 V2 }% ?2 r. {2 e0 _: ?
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
! P3 t2 A# A  v0 oejected during the impact, the red is limestone outcrop and the green areas are mostly vegetation. The impact occurred 公仔箱論壇2 M; }! Y! ]( R' t- g% B
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. www2.tvboxnow.com* V4 R( X6 e( N/ S- y
Scientists determined the structure was caused by an asteroid through clues such as the presence of maskelynite, ' W$ p. C  R& y; c4 j2 J' b
a glass that is only formed by extremely high-velocity impacts. The impact occurred around 50,000 years ago.
) o! l, I* C9 J/ RThis image was captured by the Advanced Spaceborne Thermal Emission and Reflection Radiometer on NASA’s tvb now,tvbnow,bttvb: S4 P. q# L- j
Terra satellite. It is a simulated true-color image公仔箱論壇: x* D3 `; C7 d7 o

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The Vredefort Dome in South Africa is possibly the oldest and largest clearly visible asteroid impact on Earth.
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
a 300-mile wide asteroid would look impacting Earth. This event probably would have killed everything on the planet. www2.tvboxnow.com- ^* k* \: \' k! ^; L
Fortunately, NASA says nothing this big is headed our way anytime soon.