A team that studied Australia’s Wolfe Creek crater calculated how often meteorites hit Earth with the force of massive nuclear explosions, every 180 years to be precise.
Professor Tim Barrows of Wollongong University led an international team that used two techniques to date rocks affected by the impact of the Wolfe Creek crater, revealing that he is much younger than previously thought.
“The first was to get some rocks from the edge of the crater that had been ejected when the meteor hit, and this creates a cool surface that is exposed to radiation, and we can determine how long that exposure has been,” said Barrows. “The second technique was to observe the dune field that had been diverted by the crater.”
The team discovered that a 15-meter-wide iron meteorite was more likely to hit the site 120,000 years ago, less than half of the previous estimate of 300,000 years ago.
“The amount of energy that was released when the meteorite hit was on the order of 30 to 40 times the energy released by the bomb that fell on Hiroshima,” said Barrows.
The Wolfe Creek crater is one of the best preserved craters on planet Earth, partly due to its relatively young age, but also due to its location in a geologically stable desert, which describes two-thirds of Australia, which means that the craters of Earthly meteorites found here have their best chance of longevity.
“The arid area of Australia is an excellent area in terms of meteorite preservation, there are a lot of meteorites that have been found in the Nullarbor plain, for example,” said Barrows, “but it is also excellent for preserving craters because erosion rates are very low. ” “.
Barrows and his team discovered that meteorites measured in tens of meters, such as the one created by the Wolfe Creek crater, are much more common than large meteorites, measured in kilometers, that only impact the Earth every few million years. Six other Australian craters with known impact dates were combined with new research at Wolfe Creek to produce a frequency of attacks on that area of the Earth’s surface.
“It seems that we are getting at least one large meteorite, in general, more than 25 meters or so, every 180 years,” Barrows said. “There have probably been four craters formed by meteorites that hit the Earth in the last 60 or 70 years. “
Barrows said that since most of these meteors are hitting the oceans, since 75 percent of our planet is covered with water, a meteorite of this type is unlikely to hit a population center. However, says Barrows, they are still important events in the geological history of those areas.