The View from Space: Earth's Astroid Impact Crater Remnants

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."

Why Free Scientific Inquiry and Democracy are Inexorably Linked and Indicate the Intellectual Health of our Nation

Ask any group of common American citizens about what they think about evolution and the odds are quite high that 46% of those polled will completely reject the tenets and existence of evolution. In fact, some of those polled may be so bold as to indicate that they believe that the facts for evolution espoused by Darwin and his later day followers make this group of scientific eggheads hard boiled and tools of the devil.

Roughly the same sized group of contemporary Americans, I'm not talking about those who lived sometime in the early nineteenth century, would also contend that the Earth is actually less than 10,000 years old. If you will remember from an earlier posting I made this week the actual age of the Earth is really closer to 4 billions years old.

Why are so many people so dumb one might wonder? Well there's plenty of blame to go around and a lot of it has to do with the way science is ignored by the popular media. No. I'm not talking about that next shuttle mission launch; that's important and newsworthy because you never know when one of those overused old workhorse shuttles might explode on launch or upon reentry into the Earth's atmosphere - that's your media in action; covering the spectacle while ignoring the every-day occurrences of science and its intertwining with the strength of our fledgling democracy.I'm talking about the plain fact that over the past several decades, weekly science sections in daily newspapers has shrunken by an astonishing 2/3 of what they once were. Current debates over such significant topics as global climate change have been shifted from a discussion of scientific facts and theories and place into the arena of political bigotry. In addition the voice of scientists have been muted by those of popular religious leaders and opinion makers, groups who do not rely on scientific findings to base their views but on the means and methods of propaganda to support their agendas.

An important insight into the morass in discussing scientific subjects was predicted in the famous 1959 Rede lecture at Cambridge University by C. P. Snow, a scientifically trained writer who uncovered the existence of the competition between "two cultures" that was distinguishable by a "gulf of mutual incomprehension" that pitted humanists against scientists. As the holders of power and the decision makers in western society humanists held sway over the way science would be viewed. In comparison to the humanists, the members of the scientific community were marginalized and held little prestige; they were the 'specialists' who provided the means, such as nuclear weapons for the humanists to be the agenda setters. Meanwhile, the humanists had little practice understanding of what the scientists were capable of producing; they only knew that what ever might be produced could and would be put to use in the plans the humanists had assembled. With numerous threats facing humankind, from climate change;

to pandemics; and the spread of nuclear weapons; each of which are laden with scientific fundamentals that few if many non-scientists understand.

What is the connection to democracy you ask? It lies with the free and unimpinged flow of information and knowledge. The simple matter of the fact is that we live in an age increasingly dominated by science and scientific principles which constitute nothing but meaningless jargon not only for most of the population but also for our political, cultural, and legal gatekeepers as well as the leaders of capitalist enterprises. it is time we integrate a much more precise and meaningful understanding of the necessary integration of the scientific understanding of human affairs as an integral part of civic discourse. In other words the construction of a civics that welds a scientific understanding of worldly affairs with democratic principles that involve all citizens in this undertaking.