That'll leave a dent
People have long feared the impact of a large object on our planet - and impact that could easily release the devastation of a nuclear weapon many times compounded. Objects from space that survive our atmosphere are generally meteorites, which are small particles from asteroids or comets that orbit the sun.
Once every 2,000 years or so, an asteroid the size of a football field comes in contact with the Earth. This can cause significant damage to the planet. Then, every few million years, our planet experiences an impact event. This is when an object big enough to end life as we know it collides with Earth. Scientists generally agree that an asteroid impact eliminated dinosaurs from the planet about 65 million years ago.
Life on Earth has been transformed by impact events. Not only have these impacts shaped evolution, they have created important ore deposits and land disturbances. Impacts have even helped shape and form our oceans. Here are seven images of known asteroid impact craters around the planet. (Text: Katherine Butler)
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1. Spider Crater, Australia
The Spider Crater can be found in the Kimberly area of Western Australia. This false-colour image was taken by NASA’s Advanced Spaceborne Thermal Emission and Reflection Radiometer, which is on the Terra satellite.
Shatter cones at the centre of the crater give some indication of the Spider Crater's age, though experts are uncertain. (Shatter cones are cone-shaped cone rocks with a shattered appearance that indicate an asteroid hit.) NASA believes an asteroid may have hit this area between 900 and 600 million years ago during the Neoproterozoic Era, when “Earth underwent a series of global ice ages nicknamed 'Snowball Earth',” according to NASA.
2. Manicouagan Crater, Canada
This crater in Quebec, Canada, is known to be one of the oldest and largest impact craters on the planet. Experts believe it was created some 214 million years ago during the Triassic Period. Glaciers have since played a large part in its erosion.
This false-colour image shows a green ring depression that surrounds a central peak. The ring depression contains the Manicouagan Reservoir. NASA calls this impact crater the easiest to spot from space. When astronauts are observing it from space, it looks like a ring lake and is “and as a smooth and flat feature in this topographic visualization.”
3. Barringer Crater, Arizona
The first crater to be identified as the result of an asteroid impact is the Barringer Crater, also known as the Meteor Crater. NASA believes an 80-foot-wide asteroid collided with what is now the surface of northern Arizona about 20,000 to 50,000 years ago.
Only in the past few decades have experts considered impact craters worthy of scientific notice. The origin of the Barringer Crater was questioned for many years. Fragments from a meteorite that struck the area ultimately proved that the crater was the result of an impact.
4. Vredefort Dome, South Africa
At around 300 kilometres (186.4 miles) wide, the Vredefort Dome is the largest verified impact crater on Earth. The colours swirl together to make the crater look like something Vincent Van Gogh might have imagined.
Located in South Africa, the crater is thought to be 2 billion years old. It was created by an asteroid that was only 10 kilometres in width. At the time, life on Earth consisted of microscopic plant life. Experts are sure that if evolution had been further along at the time of impact, it would have annihilated most life on the planet. The force of the impact that created it has been compared to a blast 10 times bigger than the explosion of every nuclear bomb on the planet.
For the last 150,000 years, the crater - with its landscape of mountains and hills - has served as a home for humans. The Vredefort Dome provides shelter and good grazing land.
5. Gosses Bluff, Australia
The Gosses Bluff crater in the Northern Territory of Australia is of great importance to the Western Arrernte Aboriginal people. They call it Tnorala. According to their beliefs, a group of women was dancing across the Milky Way. One of them put her baby in a carrier, which fell over the edge of the dance floor, hitting Earth and creating Tnorala.
The crater, which is 24 kilometres (almost 15 miles) in diameter, is thought to be about 142 million years old.
Australia is second only to North America in number of known impact craters. However, this may only be because the North American craters are more heavily studied than their counterparts in Australia.
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6. El'gygytgyn Crater, Russia
About 60 miles north of the Arctic Circle in eastern Russia is Lake El'gygytgyn, which is inside a 3.6-million-year-old meteorite impact crater. The crater is about 15 kilometres (about 9.3 miles) across. “In this false-colour image, red indicates vegetation, grey-brown indicates bare land, and deep blue indicates water,” NASA writes, noting that the vegetation consists of low-lying plants that make up the Arctic tundra.
Climate researchers find this impact crater particularly valuable, as its lake bed sediments contain a continuous record of past Arctic conditions. They are able to use these sediments to analyze how climate has changed over the past few million years.
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7. Bosumtwi Crater, Ghana
The Lake Bosumtwi impact crater was formed about 1 million years ago and is a sacred spot to the Ahshanti, who believe the dead come here to bid farewell to the god Twi. Fishing in the lake is allowed, but only from wooden planks and not modern boats, because there is a taboo against touching the water with iron.
Located in a dense rain forest, this African crater has been hard to study, but experts have confirmed that its creation was the result of an impact.
Its rim diameter is about 11 kilometres measured north to south and 10 kilometres east to west,” according to the Geological Society of America Bulletin. The largest impact crater on Earth is thought to be the Wilkes Land crater in the Antarctic. However, experts cannot confirm this because the crater is buried under 2 kilometres of ice.
Most impact craters eventually erode away; however, as seen here, the truly magnificent impacts still remain.
There are as many as 140 individual impact craters on Earth. NASA estimates that is about 25 percent of all the craters that exist - but most have yet to be discovered.
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