In a short article written by Betsey Mason for Wired Science Blog; Ms. Mason reveals some stunning information and pictures of the remains of impact craters on Earth caused by ancient asteroid impacts: "Asteroid impact craters are among the most interesting geological structures on any planet. Many other planets and moons in our solar system, including our own moon, are pock-marked with loads of craters. 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 structures don't last long and can be tough to come by.
"But on a few old pieces of continent, especially in arid deserts, the marks of asteroids have been preserved. One well-known example is our own Barringer crater, also known as Meteor Crater, in Arizona. The images here show some of the biggest, oldest and most interesting impact craters on the planet.
"Aorounga crater, pictured above and below, is one of the best preserved impact craters on Earth, thanks 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 unidirectional wind. The image above was taken by astronauts in the International Space Station in July. In the radar image below, taken from the space shuttle in 1994, reveals that Aorounga may be one of two or three craters.
"The Shoemaker crater in Western Australia, formerly known as the Teague crater, was renamed in honor of the planetary geologist Eugene Shoemaker for whom the Comet Shoemaker-Levy 9 is also named. The age of the crater unclear, but it could 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.
Image: NASA/USGS, 2000.
"The Manicouagan Crater in northern Canada is one of the largest impact craters known on Earth. The impact occurred around 210 million years ago at the end of the Triassic period and may have caused a mass extinction that killed around 60 percent of all species. Though the crater has mostly eroded, Lake Manicouagan outlines what is left of the 43-mile wide impact structure. The asteroid that created the crater is thought to have been about three miles wide. Today the lake is a reservoir and popular salmon fishing location.
Images: 1) NASA, STS 9 Crew, 1983. 2) NASA/GSFC/LaRC/JPL, MISR Team, 2001.
"This crazy looking structure in Western Australia is called the Spider crater, for obvious reasons. Geologists determined it was 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 the weathering of wind and water better than the softer intervening layers. The crater is somewhere between 600 million and 900 million years old and the raised area at its center is around 1,600 feet wide.
"The image above is a false-color image taken by the Advanced Spaceborne Thermal Emission and Reflection Radiometer on NASA's Terra. The true-color image below was captured by Taiwan's Formost-2 satellite.
"This crazy looking structure in Western Australia is called the Spider crater, for obvious reasons. Geologists determined it was 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 the weathering of wind and water better than the softer intervening layers. The crater is somewhere between 600 million and 900 million years old and the raised area at its center is around 1,600 feet wide.
Images: 1) NASA/GSFC/METI/ERSDAC/JAROS, U.S./Japan ASTER Science Team, 2008. 2) Cheng-Chien Liu, National Cheng-Kung University and Dr. An-Ming Wu, National Space Organization, Taiwan, 2008.
"The Gosses Bluff crater in Australia's Northern Territory sits between two mountain ranges. The raised circular feature in the center of the structure is around 2.8 miles across, but the original crater rim was probably at the edge of the surrounding grayish area. The crater was formed caused by an asteroid impact around 140 million years ago.
Image: USGS
"Clearwater Lakes in Quebec, Canada were formed by a pair of asteroid impact craters. The impacts probably occurred simultaneously around 290 million years ago. The larger crater measures 22 miles across.
Image: NASA
"The Roter Kamm crater in Namibia is hard to see in visible light, but shows up more clearly with imaging radar. The crater’s 1.5 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 the space shuttle. Irregular surfaces show up brightly and smooth areas are dark. The white splotch at the bottom of the 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 ejected during the impact, the red is limestone outcrop and the green areas are mostly vegetation. The impact occurred around 5 million years ago.
Image: NASA/JPL, 1994.
"The Lonar crater in Maharashta, India is around 6,000 feet wide and 500 feet deep and contains a saltwater lake. Scientists determined the structure was caused by an asteroid through clues such as the presence of maskelynite, a glass that is only formed by extremely high-velocity impacts. The impact occurred around 50,000 years ago. This image was captured by the Advanced Spaceborne Thermal Emission and Reflection Radiometer on NASA's Terra satellite. It is a simulated true-color image
Image: NASA, 2004
"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.
Images: NASA
An artist's rendering "of what a 300-mile wide asteroid would look impacting Earth."
Today Oct 8, 2011 Meteor Shower. Nov 8, 2011 Asteriod.
ReplyDeleteIMPORTANT NOTICE TO ALL THAT LIVE BY THE SEA OR OCEAN SHORE AT 1 FOOT TO 50 FEET ABOVE SEA LEVEL. Or with in ten miles of the coast. World Wide.
This will be a very close call i pray it is only that. Discovered on December 28, 2005 by Robert McMillan of the Spacewatch Program A potentially hazardous Asteroid known as 2005 YU55.
This Asteroid some what Large 400 meter-sized type – C, will pass by the Earth right between our moon and Earth. On November 8, 2011.
The people on Earth have not seen a Asteroid of this size in advance. One this big Has not impacted Earth in over at least 4 thousand years.
Most Objects that have a diameters over 45 meters or 147.637 ft strike the Earth approximately once every thousand years or so. Lying flat everything for hundreds of miles.
Like the TUNGUSKA 1908 SIBERIA, RUSSIA CRASH OR Tunguska Explosion. This one did not even hit the Earth with its full Impact, it burst high in the air above the ground plowing it apart into many smaller parts. Making thousands of very deep holes in the Russian forests. Many of them in dense forest far from any roads or towns.
One 400 Meters 1,312.3 ft in diameter like this one YU55 weighing millions of tons would if impacted Earth on land would darken all of the Earth not for just days but much longer.
It would change the weather not seen on Earth in over thousands of years a massive climate change to say the least.
Asteroids in our Asteroid Belt that is between the orbits of Jupiter and Mars do have collisions and some do turn into meteoroids many in the past thousands of years have come into the Earth's Atmosphere. Many of thousands of them make it into Meteorites the signs are all over the Earth, craters of all sizes.
The World and NASA will watch this one very closely.
Most likely more Earthquakes and the Oceans Tide will be strongly affected just from a near miss.
The Lord’s Little Helper
Paul Felix Schott